The Tech Elon Has Been Waiting For (EP 51)

What happens when electronics can operate at temperatures hot enough to melt aluminum? In this deep-dive episode, Lester Nare and Krishna Choudhary examine a new high-temperature memory device developed by researchers at USC, the Air Force Research Laboratory, Kumamoto University, and their collaborators. Published in Science, the experimental memristor combines tungsten, hafnium oxide, and graphene. It operated reliably at 700°C—roughly 1,300°F—retained data for more than 50 hours, and survived more than one billion switching cycles. We begin by explaining why conventional electronics and flash memory fail when temperatures rise. From deep-earth drilling and hypersonic aircraft to nuclear systems and the surface of Venus, many environments where intelligent electronics would be useful remain inaccessible to today’s hardware. Krishna then builds the memristor from first principles. We explore the history of the “missing” fourth circuit element, how oxygen vacancies create low- and high-resistance memory states, why conventional platinum electrodes fail under extreme heat, and how graphene prevents tungsten atoms from diffusing through the device. Finally, we examine the implications for artificial intelligence. Memristors can potentially store neural-network weights and perform matrix multiplication in the same physical location, reducing the energy wasted moving information between processors and memory. Could that combination of heat tolerance and energy efficiency make AI data centers in space more practical? Lester and Krishna work through thermal radiation, radiator size, power consumption, radiation resilience, and the considerable engineering challenges that remain. Support the showDonate: FFPod.com/donateFollow: @FFPod on X / Instagram / TikTok / Facebook Research and Show Notes High-temperature memristors enabled by interfacial engineering USC: A memory device that operates at 700°C The development of carbon-neutral data centres in space NASA Venus facts

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Krishna Choudhary?

  Industrial fat flash memory tops out at around 200 degrees Celsius. And above that, there's essentially nothing that works. Okay, it's a memorister, which is a memory switching device. And it's made from graphene, hafnium oxide and tungsten. And it operates reliably at 700 degrees Celsius. Really cool. I mean, it's hotter than molten aluminum. Aluminum melts at 660 degrees Celsius. If you put this thing in a vat of aluminum, it will still retain memory.

• 0:29Lester Nare?

  Hello, Internet. This is your captain speaking, Lester Nare. Joined as always by my co-host and our resident PhD Krishna Choudhary. We have a special deep dive today for you all. Be sure to check out our rundown from last week. But this week, we'll be sure to heat up the future of electronics as we look at a breakthrough in high temperature memory. This is something that Elon has been waiting for for a long time that may enable electronics that can survive lava. I'm gonna need the details. I'm gonna need to understand what's going on here. This comes from a new research paper in the Journal of Science.

• 1:12Lester Nare?

  Shout out to science from March 26, 2026. It was a collaboration between researchers at USC here in California, the Air Force Research Lab in Dayton, Ohio, and the Kumamoto University in Japan. Please correct my pronunciation. With funding for this research being provided by National Science Foundation, the Army Research Office and the Air Force Research Lab. So clearly, they think there is military applications. I'm sure it relates to hypersonics. As always, we are going to learn about the science from the ground up today because this is from First Principles.

• 2:05Krishna Choudhary?

  Today, we're covering an invention that I think is going to be a game changer for the future of computing. You know, we live in the digital age of electronics. Chips are the bedrock of our economy. And yet, all of those chips really have a Goldilocks zone when it comes to when they work. Goldilocks in the traditional sense of like, not too hot, not too cold. The, this research is getting to that not too hot part. You know, the Papa Bear that, uh, that was like too hot. The porridge was too hot. Now we're getting a chip that can withstand that porridge. Okay. These are memory chips that happen in our phone, in our laptop, in the cameras that we have here in the studio.

• 2:46Krishna Choudhary?

  They're all designed to work reliably roughly between 85 degrees Celsius, so 200 Fahrenheit for our Americans, to about 150 degrees Celsius. So 300 Fahrenheit. Okay, that's where they sit. And industrial fat flash memory tops out at around 200 degrees Celsius. Even with a lot of the heroic packaging, where you will try to insulate temperature and things like that. And above that, there's essentially nothing that works. Okay, there's no computation happening above 300 degrees Celsius. But that doesn't mean that we don't want to have computation happening at that temperature.

• 3:27Krishna Choudhary?

  Okay, there are a lot of applications that even I can think of here, not being in the field, that would be really great to have at 300 degrees or above. Okay, for example, oil and gas. Oil and gas drillers, they push deep into the earth's crust. The deeper you get into the earth's crust, the closer you're getting to the mantle where all of the magma is. So the temperature is going to go up. At five kilometers, you're flirting with like 150 degrees Celsius. That's already pushing it. At 10 kilometers, you're well past 300 degrees. And the sensor packages that we have today, when you send them down these boreholes, they need to either operate with like an active cooling thing, where like there's something with the, the drill

• 4:11Krishna Choudhary?

  that's trying to cool the sensors. That's always not convenient, right? Yeah, and then, and then they have to transmit their data to the surface in real time. They can't do any computation down there.

• 4:23Lester Nare?

  Ah, interesting.

• 4:24Krishna Choudhary?

  So then there's this like massive wiring problem that you have to deal with. The wires are going through this really hot.

• 4:32Lester Nare?

  The engineering is way more complex unnecessarily, if you could just have it.

• 4:35Krishna Choudhary?

  Yes, if you could just have like a chip that's right on top of the drill, right? That's right there, then you can have something like an autonomous downhole drill, like electronics that decides where to go right there. I mean, we've got all this AI, but we can't actually put that to use when we're going all the way down there, right?

• 4:55Lester Nare?

  If, and I'm gonna make another Armageddon reference. When we need to go to an asteroid and, and, and we need to drill, I guess that's a bad example because it's not that hot.

• 5:05Krishna Choudhary?

  Yeah, well, I mean, but even the friction is gonna create like a hot, yeah, some heat. You know, we're gonna wanna be able to do that.

• 5:11Lester Nare?

  Yeah, planetary defense.

• 5:13Krishna Choudhary?

  Yes, as always, you know, we are defense first here, not war, only defense. Now, you mentioned hypersonics. That's another big thing, right? In aerospace engineering, the inside of a jet engine or the inside of a rocket engine or the nose of a hypersonic aircraft, these things are getting to really, really high temperatures. We've covered this in previous stories where the, the temperature gets so high that chemistry starts mattering.

• 5:40Lester Nare?

  Gets a little weird.

• 5:40Krishna Choudhary?

  Yeah, and it starts getting a little weird. And we can't make any intelligent decisions on site because of the chip. The chip is just gonna get fried. And finally, the thing that Elon has been worried about and all of these tech bros are worried about is putting data centers in space, right?

• 5:58Lester Nare?

  This is the number one conversation in SF right now.

• 6:00Krishna Choudhary?

  Yeah, yeah, I mean, Elon wants to put data centers in space. He's not the only one. SpaceX had an IPO of 1.7 trillion dollars. And I think a lot of that hinges on Elon's promise that he can put AI data centers in space. We're gonna get into the details there, but there's been a lot of pushback because of fundamental physics, right? They're saying, oh, like fundamental physics is telling you that you can't put data centers in space. Well, yes and no. Okay, yes, in the sense that yes, the physics and the electronics that we have today are, it's probably not a good idea to put data centers in space.

• 6:41Krishna Choudhary?

  But with this problem, you can have innovation like the one that we're gonna talk about. And perhaps it's possible. The main problem really is that to keep a one megawatt artificial intelligence server cool in the vacuum of space, you need a radiator that's roughly the size of four tennis courts, right? That's because the space is a vacuum. There's no way to extract heat other than radiation. And, and radiation is not a great way to let go of heat because you're relying on photons.

• 7:10Lester Nare?

  It's not, is it, would you, it's like because it's not efficient?

• 7:13Krishna Choudhary?

  Yes, exactly. It's just not efficient. We're gonna get into some of the physics of that later. And the, my favorite sort of conundrum that I think this is going to solve is planetary exploration. I think you're gonna like this too. There's a reason why we have so many photos of Mars and not that many photos of Venus. Okay, Mars is pretty chill to go to. It's like kinda cold.

• 7:37Lester Nare?

  Yeah, literally.

• 7:38Krishna Choudhary?

  It's like literally, it's farther away from the sun and it's fine. Venus is closer to the earth and it's got this massive greenhouse effect, which means that it's really hard to get, put stuff down there. Actually, the, the first guys to do it were the Soviets. Venus has a surface temperature of about 465 degrees Celsius and an atmospheric pressure that's 92 times that of the earth. The Soviets put down the Soviet Venere landers and they're the only spacecraft that have ever survived on the Venus surface. But guess how long they survived? Over, under an hour?

• 8:14Lester Nare?

  Uh, it's gotta be under an hour.

• 8:16Krishna Choudhary?

  It's under an hour, yeah. It's, it's between like 23 minutes. I think the record was like two hours later on, but like two hours?

• 8:24Lester Nare?

  Yeah, yeah, no.

• 8:25Krishna Choudhary?

  Right, like the, the stuff that JPL puts on Mars has lasted like 20 years.

• 8:30Lester Nare?

  Yeah, it's two, we're talking about two decades.

• 8:32Krishna Choudhary?

  Yes, versus two hours, right? Is the best that they can do.

• 8:36Lester Nare?

  And I will note, this is for those who are TV fans. We've talked about For All Mankind on the show before, but Apple has a second, Apple TV has a second show called Star City. Okay, that looks at the Russian space program in the same alternative history timeline where they got to the moon first. And they do a whole, all of season one, part of it relates to the Venus mission.

• 8:59Krishna Choudhary?

  Really, dude, I gotta watch that.

• 9:00Lester Nare?

  And it's, it's, it's alternative reality, so yes, no spoilers.

• 9:05Krishna Choudhary?

  I love, I love that kinda stuff.

• 9:06Lester Nare?

  But it is interesting to kind of understand the technical challenges, which they brushed on at a high level in the show. But recently, I've been watching it and this brought it up as a concept. And the engineering problem is non-trivial.

• 9:21Krishna Choudhary?

  Yeah, no, completely, right? It's like going towards the center of the earth. It's the same drilling thing, high pressure, high temperature. Your electronics are gonna get completely wrecked, right? The photo we have from the Venere 9 in 1975, this is the best photo they got. It's the first image of a planet other than the earth. Credit to the Soviets.

• 9:41Lester Nare?

  Yeah, they did.

• 9:41Krishna Choudhary?

  The first image of a planet other than the earth was not the United States and Mars. It was Venus. And that's all they got, but still, that's kinda crazy.

• 9:49Lester Nare?

  But who got to the moon though?

• 9:51Krishna Choudhary?

  Yeah, that's, that's, I mean, they were like, okay, let's go, let's go the other direction. Yeah, yeah, yeah.

• 9:57Lester Nare?

  The race is actually this way, guys.

• 9:58Krishna Choudhary?

  Yeah, um, later missions, um, they were actually able to get some color photos. This is the one that lasted two hours.

• 10:04Lester Nare?

  Okay.

• 10:05Krishna Choudhary?

  And you could get some color photos. You can see the sort of yellow haze that we know that the Venus has if you point a telescope to it. But again, only two hours and you can see there's like, it, it kinda looks like the surface of a volcanic debris field because there's a bunch of volcanoes on Venus. But that's, that's it. That's all we could get.

• 10:25Lester Nare?

  And we can imagine, you know, as we continue to expand in our own local solar system and otherwise, having electronics that can survive high temperature environments is gonna become a valuable asset to expand where we can actually go.

• 10:40Krishna Choudhary?

  Exactly. I mean, I'd like to know more about the surface of Venus, right? We know, we, we have better surface images of Mars Pluto. We have, we have better surface images of Pluto than we do with large swats of Venus, which is our nearest neighbor. Venus is closer to us than the earth. And we still don't know what's under those clouds.

• 10:59Lester Nare?

  Unbelievable.

• 11:00Krishna Choudhary?

  Right, and it's just because it's just, it's, it's a completely. Messed up situation to get down there on the surface. Everything fails.

• 11:09Lester Nare?

  We can't stand the heat, so we can't go in the kitchen.

• 11:11Krishna Choudhary?

  Yeah, exactly, exactly. And into this landscape comes this paper that was published by USC. It's describing something I think genuinely new. Okay, it's a memorister, which is a memory switching device. We're going to get into what that is. And it's made from graphene, half-nium oxide and tungsten. And it operates reliably at 700 degrees Celsius.

• 11:35Lester Nare?

  That's unreal.

• 11:36Krishna Choudhary?

  700 degrees. Yeah, they've they've raised the temperature like by a factor of more than two.

• 11:43Lester Nare?

  And so there's something fundamental. There's a there's a real breakthrough here. That's beyond an iterative.

• 11:49Krishna Choudhary?

  Yes, yes, yeah, there's it's it's I think it's really cool. I mean, it's hotter than molten aluminum. Aluminum melts at 660 degrees Celsius. If you put this thing in a vat of aluminum, it will still retain memory. It's hotter than the surface of a lava flow on Earth. Not all lava flows. I know there's going to be people in the comments being like, no.

• 12:10Lester Nare?

  The volcanologists.

• 12:10Krishna Choudhary?

  Yeah, yeah, the volcanologists is going to be like, no, lava is hotter than that. Actually, there is a volcano in Tanzania, the old Doño Lengay volcano, where the lava is 600 degrees Celsius. Okay, so there exists a lava on Earth where I could put this chip and it would still work fine. So the tagline still kind of works, right? If you if you took it to Hawaii and put it in the lava in Hawaii, it would not. I think Hawaii's is like 1,000 plus, but it perhaps might, and we'll get into that later.

• 12:42Lester Nare?

  We're on the path.

• 12:43Krishna Choudhary?

  Yeah. The other crazy thing about this is the chip, the the memorister device, it maintained stable data retention for 50 hours.

• 12:54Lester Nare?

  Really?

• 12:55Krishna Choudhary?

  50 hours, and it retained that data retention after a billion switching cycles without failure.

• 13:02Lester Nare?

  So this is both high temperature and long duration.

• 13:06Krishna Choudhary?

  Yes.

• 13:06Lester Nare?

  Comparatively to where we were before.

• 13:08Krishna Choudhary?

  Yeah, and the physics is actually like it gives you both.

• 13:12Lester Nare?

  Which is because both are different.

• 13:14Krishna Choudhary?

  Yeah.

• 13:14Lester Nare?

  It's like a graphene different axis. And you can have high temperature. It's like, okay, great, but it's a microsecond.

• 13:19Krishna Choudhary?

  Yeah, yeah, but and here what's what's cool is it's the same physics that's giving you both.

• 13:24Lester Nare?

  Ah, okay.

• 13:26Krishna Choudhary?

  Which I think is really, really cool.

• 13:27Lester Nare?

  Yeah, that is.

• 13:27Krishna Choudhary?

  It's by I think it's by a large margin, the highest temperature at which any nonvolatile memory has ever been demonstrated to work.

• 13:35Lester Nare?

  This is.

• 13:36Krishna Choudhary?

  Yeah, it's it's really, really cool. And I mean, why should why should like normal people care? Okay, not scientists.

• 13:41Lester Nare?

  Sure.

• 13:41Krishna Choudhary?

  Well, I think the border between environments where we can put intelligent electronics and environments where we cannot is about to shift dramatically.

• 13:51Lester Nare?

  And then our understanding of everything about the world around us changes in a in a very big way.

• 13:55Krishna Choudhary?

  Yeah, I mean, it affects how we drill energy, how we explore planets, how we monitor volcanoes, how we put data centers in space. That has a lot of social and political implications for our society. Because then maybe maybe we don't need to, you know, like, take everyone's water.

• 14:13Lester Nare?

  If you don't want a data center in your backyard, this story matters a lot because we can just put them in space.

• 14:19Krishna Choudhary?

  Yeah, yeah, I mean, it's it's one of these like quiet material science results that it doesn't make the front page of the New York Times. But I think it's going to expand the frontier of what our civilization can do.

• 14:33Lester Nare?

  You're saying there's a chance.

• 14:34Krishna Choudhary?

  Yeah, and I think I think I think it's an incredible story.

• 14:37Lester Nare?

  We are going to get into the details of I this has been such a big conversation in the business and technology world. We are so over leveraged on AI in the US in terms of its impact on our GDP. Everyone's saying it's fine because we're going to put data centers in space. And it's been very contentious. As a one aspect of that larger conversation, this the potential for this to be an enabling layer is interesting. But before we get into the details of that story, a brief note of housekeeping. For our longtime listeners in FFP Nation, welcome back. If you happen to be catching this episode for the first time,

• 15:22Lester Nare?

  it is the two of us here bringing you the latest breaking science news every week. And any way that you can help to support the show so we can combat against the billionaire algorithms, like, share a comment, bring it to Journal Club, put it into the group chat. All of those things help us reach more people with the way in which our world is changing and growing because of the advances we have at the frontier of science. Our website has all of our episodes, all of the research papers and show notes that we cover. So if you are someone who's a grad student, a postdoc, or someone who just really wants to get actually more into the weeds of any of these stories,

• 16:06Lester Nare?

  go to ffpod.com. You can check out our research paper library. If you want to support the show, you can donate at ffpod.com backslash donate. And you can also check out the merch shop if you want to let the world know that you yourself are a member of FFP Nation. But enough of the riffraff. Let's get back to this very juicy story. I do like my steaks medium rare. But I guess I can make it much quicker if I do it at 700 degrees Celsius.

• 16:38Krishna Choudhary?

  Yes, yeah, it would it would only cook the outside like micron. And then it would be all rare. Gordon Ramsay would love that. So let's first talk about why the conventional electronics that are in our phone, that are in the laptop, everywhere else, why they fail at high temperature.

• 16:58Lester Nare?

  Why I can't bring my iPhone and put it in a lava flow?

• 17:00Krishna Choudhary?

  Yeah, yeah, yeah, I'd like to.

• 17:02Lester Nare?

  Yeah, I could put it in water.

• 17:03Krishna Choudhary?

  Yeah, but but lava lava is something you can't do. Okay, the physics of high temperature failure. We first have to understand the traditional CMOS architecture that is at the base of all of our technology. This is complementary metal oxide semiconductor. These devices fail at around 200 degrees Celsius. Here's how it usually works. Okay, so at zero Kelvin, which means absolute zero, everything is everything is stationary. Silicon isn't is a insulator. What ends up happening is atoms have something called a conduction and a valence electron shell. Okay, they've got parts where valence electrons can occupy all of the shell.

• 17:48Krishna Choudhary?

  So there's nothing going on. All of the shells are occupied, right? Then there's a conduction shell. There's a conduction energy level where there's like one or two electrons hanging out. And those electrons are the ones that skip from one atom to the next to the next. And they create current, which is what we use. Okay, now at zero degrees Kelvin, all of silicon's valence band is completely filled. If you put a bunch of metal and a bunch of silicon together, the gap between the conduction band and the valence band gets bigger just because of neighboring effects. It's like it's like the the neighboring atoms start pulling on your own energy gaps.

• 18:31Krishna Choudhary?

  And it expands the gap between these two energy bands.

• 18:35Lester Nare?

  The wiggle craze starts getting more intense.

• 18:37Krishna Choudhary?

  Exactly. And so at finite temperature, what you can do is you can bump an electron. You get some wiggle, right? Because like there's jiggling happening, there's photons that are at some energy level. That's going to come in, strike an electron. The electron is going to move up to the conduction band. And then voila, you can have a little bit of conduction. Okay, now, let's get into exactly how this happens. We've got a video that shows exactly how this conduction and valence band works. So on the bottom, you've got your silicon. You've got all of the sites that are now occupied by electrons, which are in the in the blue.

• 19:12Lester Nare?

  It's like the housing market.

• 19:13Krishna Choudhary?

  Yeah.

• 19:14Lester Nare?

  Thing on the market.

• 19:14Krishna Choudhary?

  Yeah, yeah, yeah, there's no openings. Now, all of a sudden, somebody sells a house. So an electron from the valence band moves into the conduction band. Now that conduction band electron can move around and create a current. Notice at the same time, the hole that was left in the valence band can also move around. It's like you have a bunch of packed theater seats and everybody moves one seat over. But then the the the empty seat can can start moving around too. That's a positive charge in some sense, right? Because it's a hole, the electron has gone away, so it's left a positive hole. And that hole can move around in the same sense that the electron can also move around.

• 19:55Lester Nare?

  Because it's attracting because it's that empty space and it needs to be filled.

• 19:58Krishna Choudhary?

  Yeah, yeah, yeah.

• 19:59Lester Nare?

  The movement.

• 20:00Krishna Choudhary?

  Yeah, the movement, the actual movement, the physical movement that's happening is always electrons. Right, it's the negative charge carriers. But the the the the sort of. Thing that matters in the valence band is that positive hole.

• 20:14Lester Nare?

  Right.

• 20:14Krishna Choudhary?

  That's moving around, right?

• 20:16Lester Nare?

  It unlocks the stationary state.

• 20:19Krishna Choudhary?

  Yeah.

• 20:19Lester Nare?

  That exists because it's now moved up to.

• 20:21Krishna Choudhary?

  Yeah, yeah, yeah, exactly. And so you can have two different types of semiconductors here. You can, engineers can make silicon switches using either phosphorus or boron. You can dope the silicon with either phosphorus or boron. And then these artificially dictate how many charge carriers you're gonna get. Are you gonna get more electrons in the connection man? Are you gonna get more holes? So that's where you get, if you've ever heard of like P type and N type semiconductors? The N type is the negative type semiconductor. Because the electrons are the ones that are moving around. The P type is the positive type semiconductor because the holes are the ones that are moving around. And when you combine the two, you get things like LEDs, transistors. But at too high of a temperature, you're gonna get wrecked. Why?

• 21:05Krishna Choudhary?

  Because if you have too high of a temperature, everything is gonna go into the conduction man because there's so much jiggle. And then I'm just gonna get a short circuit. It's always gonna be conducting. With a transistor, I'd like to control when it's conducting current for a one. And when it stops conducting current and becomes an insulator for a zero. But at a high enough temperature, it's always gonna be conducting. Because there's so much jiggle that the electrons are just like, oh, I'm just gonna, I'm free to move around.

• 21:31Lester Nare?

  Everything moves, okay. And so part of what we're saying is we're trying to engineer a level of control of how this movement happens. And at high temperatures currently in our traditional chips and systems, they are unable at high temperatures, you lose the ability to engineer and control.

• 21:49Krishna Choudhary?

  Yeah.

• 21:49Lester Nare?

  The jiggle, the movement. How things move like to the conduction layer.

• 21:54Krishna Choudhary?

  Yeah.

• 21:54Lester Nare?

  And back.

• 21:55Krishna Choudhary?

  Yeah, yeah, you can't control the transistor going from a one to a zero. It's just always gonna be a one.

• 21:59Lester Nare?

  Right, right, because it's always.

• 22:01Krishna Choudhary?

  Yeah, and that's the bedrock of computation.

• 22:03Lester Nare?

  Right.

• 22:03Krishna Choudhary?

  Right? Now, people have managed to make the band gap way bigger. Because if you make the band gap way bigger, then the temperature might not be enough to actually put it up.

• 22:13Lester Nare?

  Right.

• 22:13Krishna Choudhary?

  Right? And then, and then you can like preserve this transistor property. But these are authors, the authors of the paper that we're talking about, they cite this research from NASA research.

• 22:25Krishna Choudhary?

  It shows that you can, you can get all the way up to 800 degrees Celsius. But memory is still an issue, okay? You've created a sort of circuit element here, digital integrated circuit. But non volatile memory, something that retains data even when it's powered down, right? That the stuff that's in our RAM.

• 22:43Lester Nare?

  Yes.

• 22:44Krishna Choudhary?

  Like I, I turn off my computer, it's not like I'm gonna lose.

• 22:46Lester Nare?

  Everything.

• 22:47Krishna Choudhary?

  Everything, right? That kind of stuff is still not up to that scale.

• 22:53Lester Nare?

  So through public funding, we discovered that it's possible to go above 800. But the, the issue still remains, memory does not, in this context, have that high temperature limit.

• 23:06Krishna Choudhary?

  Exactly, and if we wanna do anything, we gotta store data, right? We gotta store weights if we wanna do a neural network. We gotta store what the algorithm is supposed to do if, even if without the AI stuff, right? If, it's just like instructions on what to do. That is stored in your RAM. And if the RAM fails, but like your, your circuit is doing fine, what's it gonna do? There's no instructions.

• 23:26Lester Nare?

  Right.

• 23:26Krishna Choudhary?

  Right?

• 23:27Lester Nare?

  Right.

• 23:27Krishna Choudhary?

  So most of the applications that we have, like in our computer, in, in the phone, they use something called flash memory. This also uses a transistor. This is the MOSFET transistor, where you combine a P and an N type. And it runs into the same issue with the high temperature because you're using P and N types, right? And if, even at like a low temperature, like room temperature, right? Consumer electronics like the flash in our, in our computers, it wears off after about 10,000 to 100,000 read write cycles.

• 24:01Lester Nare?

  Right, so they're not, they can't run forever.

• 24:04Krishna Choudhary?

  Yeah.

• 24:04Lester Nare?

  There, there's deterioration. Doing work deteriorates just like our own human body.

• 24:09Krishna Choudhary?

  Yeah.

• 24:10Lester Nare?

  As an athlete, you can't be an athlete forever. Your body eventually gives up. Similarly, in this context, flash memory deteriorates at some time interval.

• 24:21Krishna Choudhary?

  Exactly, yeah, exactly. And so because of that, people have been slowly looking at other substrates of computation. Specifically, something called resistive memory, R RAM, okay? This is resistive random access memory. And to understand that, we really have to understand something called the MEMRister. Okay? Let's go back to 1970. There are three types of fundamental circuit components. The resistor, the inductor, and the capacitor. This is the stuff of undergraduate physics. And if you're an electrical engineer, I'm really sorry for your loss. But you probably, you probably deal with this every single day, right?

• 25:03Krishna Choudhary?

  A resistor is something that resists electric current. So it drops a voltage across a resistor. And an inductor is something that takes a changing current and creates another current that's going in the opposite direction. So it kind of stores energy using a change in current. And a capacitor is something that stores energy using charge, okay? Now, Leon Chua in 1971, he was at UC Berkeley. He said, let's look at these three components that we've got. We've got a capacitor, right? A capacitor is something that has a relationship between charge and voltage. If I store a bunch of charge, that stores a voltage difference.

• 25:48Krishna Choudhary?

  I've got a resistor, that's a relationship between voltage and current, right? As current goes through, there's a voltage drop. And I've got an inductor. That's something that has to do with current and magnetic flux, okay? There's four variables, though.

• 26:07Lester Nare?

  Right.

• 26:08Krishna Choudhary?

  And there's only three components.

• 26:10Lester Nare?

  Right, so for those who may be audio listeners, we're looking at a square. It kind of looks like those, uh, those one, two, three, four. I don't know what you call it.

• 26:20Krishna Choudhary?

  Oh, the, yeah, the, yeah, the thing we used to do in elementary school.

• 26:24Lester Nare?

  Yeah.

• 26:24Krishna Choudhary?

  That would tell me like what my fate was.

• 26:26Lester Nare?

  Yeah, the paper thing.

• 26:27Krishna Choudhary?

  Yeah.

• 26:27Lester Nare?

  You can let us know in the comments.

• 26:28Krishna Choudhary?

  Yeah.

• 26:29Lester Nare?

  But on each of the four sides, you have exactly the components you mentioned. And each of the four corners, you have the charge voltage, current, and flux. And the point here being, we've talked about every relationship at one side of the square.

• 26:42Krishna Choudhary?

  But one side of the square, right? There should be, Leon Chua decided, there should be a relationship between flux and charge.

• 26:52Lester Nare?

  The flux capacitor.

• 26:54Krishna Choudhary?

  In some sense, yeah, yeah. And he deemed this thing the MEMRister. He said, there should be something out there, okay? This is a component where the resistance changes dynamically based on the charge flow. And he, he ruled that if there is such a relationship, what this thing is going to do is it's going to remember the state when the power is off, okay? Let's, the telltale sign, he also showed, okay, if, if experimenters are looking at this thing, he was a theorist. And he said, if experimenters are looking at this thing, all you gotta do is look at the IV curve, okay? The, um, the IV curve is the current and the voltage.

• 27:32Lester Nare?

  Current on the Y.

• 27:32Krishna Choudhary?

  On the two axes.

• 27:33Lester Nare?

  Voltage on the X.

• 27:34Krishna Choudhary?

  Yes, okay? And if we look at the IV curves, they're all very unique. On the top left, that's a normal resistor, okay? As I increase the voltage, I'm gonna increase the current across the resistor. And there you've got a line. This is a nonlinear resistor. A linear resistor would be, like the stuff that we do in undergrad physics is just like, oh, V equals IR. That's not entirely true, right? The R is a function of the V. So it, it, there's gonna be like some nonlinear resistance where like at low voltage, the resistance is not that high. And then at high voltage, the resistance is way higher, things like that.

• 28:13Krishna Choudhary?

  Or maybe, no, it's the other way around. At a high voltage, the resistance is lower because you know, there's more pull. So like the, it's easier to shuttle electrons through. Okay, so that's what we're seeing in the top left corner, okay? On the top right corner and the top, in the bottom left corner, we're seeing the IV curves for a capacitor and an inductor. Okay, those things cycle around. Those things, and this is something that everyone knows from, you know, if you've ever done RC circuits, you'll, you'll know that there's an oscillation that happens in RC and RL circuits especially. If you, if you combine a capacitor and an inductor, the capacitor gets charged and the inductor doesn't get charged. And then the inductor gets charged, the capacitor gets discharged. So there's a cycling that happens.

• 28:55Krishna Choudhary?

  And that is something that is characteristic of like sine and cosine. You got the unit circle, the X axis is sine, the Y axis is cosine, great. Leon Chua said, I should be looking for something called a MEMRister, where charge and magnetic flux are related to one another. And what I would see is a curve that looks like a loop, a figure eight loop.

• 29:24Krishna Choudhary?

  And the challenge is, there is no way to combine the other three curves to get that fourth curve.

• 29:33Lester Nare?

  Interesting.

• 29:34Krishna Choudhary?

  Okay, it is an independent element in electronics.

• 29:38Lester Nare?

  It's fundamental, it's not derivative.

• 29:40Krishna Choudhary?

  Yes, exactly, you know what, you see what I'm saying?

• 29:42Lester Nare?

  Yeah.

• 29:43Krishna Choudhary?

  It's like, it's like, you can't make, you can't make an electron out of quarks.

• 29:47Lester Nare?

  Right.

• 29:48Krishna Choudhary?

  Right, similarly, you can't make a memorister by just cleverly placing resistors, capacitors, and inductors together. This is an independent component that is one of the four fundamental components of electronics.

• 30:01Lester Nare?

  And this sort of goes back to our previous visual, which, you know, in this context of those four parts, you needed, this is sort of the missing piece to the puzzle of the fundamental elements.

• 30:12Krishna Choudhary?

  Yeah, and it's just a mathematical argument.

• 30:15Lester Nare?

  Which is so.

• 30:15Krishna Choudhary?

  Which is so cool.

• 30:16Lester Nare?

  Right.

• 30:17Krishna Choudhary?

  To think about.

• 30:17Lester Nare?

  Right.

• 30:18Krishna Choudhary?

  Right, that it's just like, there's, there's four variables, we've only got three components, there should be a fourth one.

• 30:23Lester Nare?

  Theorists have value, everybody, okay?

• 30:26Krishna Choudhary?

  It's, it's very cool, and one more thing I want to say about the memorister IV curve, right? Notice that for a capacitor and an inductor, at zero voltage, there is a non-zero current. Okay, that means it can't store data, because if I turn the thing off, there's gonna be current, and that's gonna dissipate whatever the, the stuff was happening, right? A resistor could store data, because at a zero voltage, there's zero current, but it only stores a one. It's whatever the resistance is, so it's not really storing anything. If we go back to Claude Shannon's information theory, I need two things to store data, I need a zero and a one. A memorister, on the other hand, at zero voltage, it can be in two states.

• 31:11Krishna Choudhary?

  It can be in a low resistance state, or a high resistance state.

• 31:15Lester Nare?

  This is so good.

• 31:16Krishna Choudhary?

  Right?

• 31:16Lester Nare?

  This is so good.

• 31:17Krishna Choudhary?

  Now, all of a sudden, people start paying attention, because this could be a substrate for non-volatile memory. Meaning, I turned the thing off, but depending on the history of where I was on the curve, I could be in either a low resistance state, or a high resistance state. If I can sense that, that's my zero and one, computers.

• 31:35Lester Nare?

  As a quick visual analogy here, because we're basically looking at this figure eight that's kind of like a racetrack, you remember Hot Wheels as a kid?

• 31:42Krishna Choudhary?

  Yeah, yeah, yeah.

• 31:42Lester Nare?

  So you remember how you could have the, you can have a figure eight like that, but one side would be going under, and then it would come back and it'd be going over, and that's kind of what we're saying, where it can be in two states at that center point.

• 31:52Krishna Choudhary?

  Yep.

• 31:52Lester Nare?

  It can be on the top part of the Hot Wheels track, or on the bottom part

• 31:56Krishna Choudhary?

  Yes.

• 31:56Lester Nare?

  of the Hot Wheels track.

• 31:57Krishna Choudhary?

  Yes.

• 31:57Lester Nare?

  And that's, that mechanism's how we're storing the zero and one, how we're able to have two states, which means we can have a zero, and we can have a one.

• 32:04Krishna Choudhary?

  Exactly, yeah, and for the Formula One fans, the only circuit that does this is Suzuka in Japan. It's the, there's a figure eight that's beautiful, one day we'll go. So, the theorist has done his job, he's like, there should be this thing, and specifically, this is what you guys should look for.

• 32:22Lester Nare?

  So now.

• 32:25Krishna Choudhary?

  It takes forty years.

• 32:26Lester Nare?

  Oh my god.

• 32:27Krishna Choudhary?

  Nearly forty years. Stanley Williams at Hewlett Packard Labs, so that's HP Labs, I love these Nature articles that are just like, bombshell articles, because the title is just a banger every single time. The Missing Memorister Found. After, it's nearly forty years after Leon Chua postulated that this fourth passive element should exist.

• 32:51Lester Nare?

  Yeah.

• 32:54Krishna Choudhary?

  Stanley Williams announces it in Nature, and he shows that there is a memorister that he's created using titanium dioxide and platinum electrodes, and it uses something called oxygen vacancy migration.

• 33:06Lester Nare?

  I just want to note that, this, we're talking about 2008.

• 33:09Krishna Choudhary?

  Yeah.

• 33:10Lester Nare?

  Very soon. We were in high school.

• 33:12Krishna Choudhary?

  Mm-hmm.

• 33:13Lester Nare?

  Uh, so it wasn't.

• 33:14Krishna Choudhary?

  Isn't that crazy?

• 33:15Lester Nare?

  It wasn't that long ago.

• 33:16Krishna Choudhary?

  It wasn't that long ago, no, we were in high school when the first memorister, like, when it went from theory to reality.

• 33:22Lester Nare?

  Right, and it's still at a research, uh, stage level. We're not talking about in-end consumer products.

• 33:29Krishna Choudhary?

  Yeah.

• 33:30Lester Nare?

  The iPhone came out a year before this.

• 33:32Krishna Choudhary?

  Yeah, that's crazy.

• 33:34Lester Nare?

  Just to, just to put it in time context.

• 33:36Krishna Choudhary?

  Wow.

• 33:37Lester Nare?

  Which is.

• 33:37Krishna Choudhary?

  That's a good way to, yeah, that's a good way to think about it, yeah. I mean, we had an iPhone before we even knew that a memorister was possible.

• 33:44Lester Nare?

  Which is so crazy.

• 33:45Krishna Choudhary?

  That's.

• 33:45Lester Nare?

  Knowing, knowing what we use it for now.

• 33:47Krishna Choudhary?

  Yeah, yeah, I mean, it's insane, okay, so, let's, let's talk about this valence charge mechanism that I was telling you about, about how the memorister works. Here's the idea, um, so, I told you, right, he, he got a titanium electrode, a platinum electrode, and in the middle were oxygen vacancies. Now vacancies is something that I alluded to earlier, when I was talking about the holes, the holes are vacancies, in the sense that I have taken something out, but now those, those holes, where I took that thing out, those are mobile, just like the, the, the stuff that I took out. Those are mobile elements, and if those mobile elements can rearrange, they can create electronic components on their own, right?

• 34:29Krishna Choudhary?

  In the same way that a P-type semiconductor can use the holes to do all of its electronics.

• 34:36Lester Nare?

  The point being, that vacancy is not, uh, stationary, it has the ability, independent of the thing that's left, to move on its own.

• 34:44Krishna Choudhary?

  Yeah, exactly.

• 34:45Lester Nare?

  Okay.

• 34:46Krishna Choudhary?

  So, um, let's get into a little bit more about how these oxygen vacancies work, because this is gonna be the central thing we need to understand about why the physics of this modern paper is working, okay? When you have these two electrodes, you've got a positive electrode and a negative electrode, right? You, you, what you do is a switching process, okay? So, this is effectively how it works. Let's say I've got a top electrode and a bottom electrode, in this case, it's like silver and titanium on, on the bottom, but it doesn't really matter what the identity of the two electrodes are, yet, it's gonna matter later.

• 35:29Krishna Choudhary?

  What happens is, in order to understand what this valence charge mechanism is, let's, let's try to think of an analogy, a simple analogy, okay? Imagine like a really thick, densely packed forest, like the forests of Endor in the Star Wars Episode VI Return of the Jedi.

• 35:47Lester Nare?

  Okay.

• 35:47Krishna Choudhary?

  Okay?

• 35:48Lester Nare?

  Okay.

• 35:48Krishna Choudhary?

  Now, if you remember, the forests of Endor, they had those like, motorbike thingies, um, I actually looked up what they were called, they were called forest motorbikes, seventy-four Z speeder bikes, okay? Remember, like, they, they, they like, zoom through the forest at really, really high speed? Now imagine a really, really dense forest, okay? If you've got a speeder bike in a really, really dense forest, you're gonna crash.

• 36:14Lester Nare?

  Yeah, you have to be in a Lewis Hamilton.

• 36:16Krishna Choudhary?

  Yes, yes, and even that, eh, you know, like, like, I'm talking about, like, there's, there's a tree literally everywhere.

• 36:24Lester Nare?

  It's, it's, it's not, it's not feasible.

• 36:25Krishna Choudhary?

  It's not gonna work, it's not gonna work. So, what you could do instead is have a bulldozer come in, or let's say a really high wind, and that's gonna take down some of the trees.

• 36:35Lester Nare?

  Yeah.

• 36:37Krishna Choudhary?

  Okay, when you take down some of the trees, that's kind of like creating oxygen vacancies in something like a transition metal oxide, like hafnium oxide or titanium dioxide, right? These are transition metal oxides that are metals bonded to oxygen, that's in the middle, sandwiched in between the two electrodes, right? If I've got an electric field, the oxygen, which has these like, it's, it's just got these properties where it wants to go towards the negative electrode, right? Um, this is why oxygen is so reactive, and why it rusts everything, um, the oxygen is gonna start moving. When it starts moving, it's gonna leave behind holes, okay? So it's kind of like the trees are coming down, and now I've got a pathway. Now, my motorbike can move really fast.

• 37:22Krishna Choudhary?

  The motorbike in this analogy represents the electron. The electron is piggybacking on these vacancies.

• 37:29Lester Nare?

  And, and it's, and part of your point is being, until the wind or the bulldozer comes and knocks the trees over, which is the oxygen leaving, um, the electrons can't move through.

• 37:42Krishna Choudhary?

  Yeah, so that would be a high resistance state, right? That's one of the states that we were thinking a memorister should have. It's got a memory, right? There was no wind, and so I am at a high resistance. Now, all of a sudden, I applied an electric field, I got a low resistance. Can I go backwards? Yeah, just apply the electric field in the other direction, the trees stand up, low resistance.

• 38:03Lester Nare?

  Got it, got it.

• 38:04Krishna Choudhary?

  Right?

• 38:05Lester Nare?

  Yes.

• 38:05Krishna Choudhary?

  This is the mechanism behind the switching behavior, the set and the reset that we think of in Memristors, that's the memorister jargon, it's like, you set it to the low resistance state, so then there's like, conduction happening, so that's your one, let's say.

• 38:19Lester Nare?

  Yes.

• 38:19Krishna Choudhary?

  And then you reset it back to the high resistance state, so then the, the trees are all up, the vacancies are back, the oxygen is back, I mean, there's no more vacancies, and the electrons don't have a highway to go through.

• 38:31Lester Nare?

  And what's interesting about this is you can go, you have the ability to return to, to return back and forth in between each of these states.

• 38:39Krishna Choudhary?

  Exactly, so now you've got a cycling.

• 38:40Lester Nare?

  Right.

• 38:41Krishna Choudhary?

  And that's something that you need for non-volatile memory.

• 38:43Lester Nare?

  Right.

• 38:44Krishna Choudhary?

  Okay, that's effectively what this vacancy mechanism is.

• 38:49Lester Nare?

  Mm-hmm.

• 38:49Krishna Choudhary?

  Got it?

• 38:50Lester Nare?

  Mm-hmm.

• 38:50Krishna Choudhary?

  Now, a lot of times now, we're gonna try and use hafnium oxide. The advantage here is that hafnium oxide is something that silicon chipmakers have already been using in transistor gate stacks. It will, it's already replaced the silicon dioxide.

• 39:07Krishna Choudhary?

  Transition metal oxide in the famous high K dielectric constant metal gate transition that happened in like 2007. I wasn't aware of this, obviously, because I was in school. But in 2007, like, there was sort of a plateau on Moore's law. Because we couldn't get stuff smaller. And then, and then somebody decided, hey, actually, we can use hafnium oxide. That reduces power leakage. And it allows these transitions. It allows these transistors to shrink even further without having a significant decrease in performance.

• 39:39Lester Nare?

  The smaller you get, right, the harder it is to keep the same level of performance.

• 39:43Krishna Choudhary?

  Yeah. Yeah, because you're trying to dissipate heat. The smaller you get now that the heat is starting to mess with the components themselves. And so this hafnium oxide, it's CMOS compatible. It scales to very small dimensions. It switches fast and it shows really good endurance. Right? And by the mid 2010s, all the major semiconductor companies, that's like Samsung, Micron, TSMC. They all have active memorister R RAM development programs and they still do.

• 40:10Lester Nare?

  And, and just to make, just to make a quick clarification point. So chipmakers were already using this for other chips prior to using it in Memristors.

• 40:20Krishna Choudhary?

  Yeah.

• 40:21Lester Nare?

  And so part of it was like, they had the industrial scale, working with this particular material. And so they were like, it would be ideal if we could use the same thing we already do at scale.

• 40:34Krishna Choudhary?

  Yeah.

• 40:34Lester Nare?

  In another chip type.

• 40:35Krishna Choudhary?

  Exactly.

• 40:36Lester Nare?

  Is that fair?

• 40:36Krishna Choudhary?

  That's exactly right. And so the original paper that was by Stanley Williams, that one used titanium dioxide as the transition metal oxide. But people have rapidly switched now to hafnium oxide as the sort of sandwich, the, the thing in between the sandwich. Okay. Um, now we've got hafnium oxide. Okay, that's the meat in between the sandwich. What do we want to use for the electrodes? Usually we use tungsten and platinum. Why tungsten? Well, tungsten is, has a very high affinity for oxygen. So that's good. This is trying to get the oxygen. Um, and it's also really good at withstanding high temperatures. That's why the Thomas Edison light bulbs use a tungsten filament. Right?

• 41:20Krishna Choudhary?

  And here we've got a zoom in of one of those filaments. It's made out of tungsten because it's not going to melt. Okay? So that makes sense. The basic idea now to make this memorist is the following. We've got a top electrode. We've got a bottom electrode, tungsten, hafnium oxide, something else. And we use the oxygen vacancies in the hafnium oxide to transport electrons and turn that highway on or off. Okay? That's effectively the idea.

• 41:52Lester Nare?

  And I'm guessing the idea then here is whatever is on the opposite side of the tungsten, depending on what it is, changes the dynamics of the back and forth. And so there's fertile ground to optimize for different use cases.

• 42:08Krishna Choudhary?

  That is exactly right. And, and let's, let's stay here. Okay? So you, you called it. The top is tungsten. The meat in the middle is hafnium oxide. What should go on the bottom? Okay? For a long time, people have been talking about platinum. Usually you want some kind of inert metal. It's a metal that doesn't like react with stuff. Right? Because obviously if it reacts, that's going to cause performance degradation. So platinum is a pretty good metal. This is where the valence charge mechanism takes over. Right? The problem is when you pump up the temperature, at high temperature, the tungsten starts diffusing.

• 42:50Lester Nare?

  Hmm.

• 42:51Krishna Choudhary?

  Right? If you get into a high enough temperature, the tungsten now starts jiggling around and the tungsten starts exploring the forest.

• 42:59Lester Nare?

  And we don't want that.

• 43:00Krishna Choudhary?

  We don't want that.

• 43:01Lester Nare?

  We just want the oxygen.

• 43:02Krishna Choudhary?

  We, we want only the oxygen to move around, create these vacancies, and then there's a highway. But if the tungsten starts moving around, all of a sudden, maybe you've got filaments of tungsten and maybe filaments of platinum that are coming together. And if those two meet, you've got a shorted circuit.

• 43:16Lester Nare?

  Hmm.

• 43:18Krishna Choudhary?

  Now, there, there's no way to, I mean, even if you cut down all the trees, you've just paved a highway.

• 43:25Lester Nare?

  For the, yeah, yeah, yeah. And there's no, they can no longer cycle.

• 43:28Krishna Choudhary?

  Yeah, yeah. Why would anyone take the trees? You just go through the highway.

• 43:32Lester Nare?

  Right.

• 43:32Krishna Choudhary?

  Right? You go through the tungsten and the platinum filaments. And that's been the big problem.

• 43:36Lester Nare?

  Okay.

• 43:37Krishna Choudhary?

  Right? They mix in ways that destroy this precise nanoscale structure. Platinum and tungsten is not the way. Okay? You're going to effectively short circuit at high temperatures. At low temperatures, this thing is working.

• 43:48Lester Nare?

  Great.

• 43:49Krishna Choudhary?

  Right? But you, you start pumping this thing up to 500, 600, 700 degrees Celsius. All of a sudden, the, the metal atoms in the two electrodes, they start getting agitated.

• 44:01Lester Nare?

  This, this is giving me a, a feeling similar to the hypersonics episode we talked about where Navier-Stokes gets weird at higher temperatures. And so there's different regimes.

• 44:14Krishna Choudhary?

  Yeah.

• 44:14Lester Nare?

  Depending on the temperature band you're working in.

• 44:16Krishna Choudhary?

  Yeah.

• 44:17Lester Nare?

  And I'm, I'm just making, making the connection between the two things.

• 44:21Krishna Choudhary?

  Yeah, yeah. Different physics starts mattering, right?

• 44:23Lester Nare?

  Right.

• 44:23Krishna Choudhary?

  It's like, it's like the, the titanium to titanium bond.

• 44:26Lester Nare?

  Yeah.

• 44:27Krishna Choudhary?

  Is now smaller than the thermal noise.

• 44:30Lester Nare?

  Yeah.

• 44:30Krishna Choudhary?

  And so the titanium is like, all right, I'm going to dip out. Let's start exploring. I don't know. I'm going to go this way. And the platinum is like, hey, you know?

• 44:37Lester Nare?

  Yeah. And, and the structure, the way you've kind of laid it out now, that, that makes sense in terms of, okay, we, we've discovered the fourth side, which is the memorister. We've figured out ways in which, because of the way the industry was at the time, what kind of works and is good for most of the use cases we thought we needed.

• 44:55Krishna Choudhary?

  Mm hmm.

• 44:56Lester Nare?

  But then as we got to higher temperatures, physics gets different. And it does, are the current regime of tungsten and platinum.

• 45:05Krishna Choudhary?

  Doesn't work.

• 45:05Lester Nare?

  Doesn't work.

• 45:06Krishna Choudhary?

  Yes, exactly. And now we get to the paper. Okay, this was out in Science. Um, shout out triple A S.

• 45:13Lester Nare?

  Woo!

• 45:14Krishna Choudhary?

  Um, high temperature Memristors enabled by interfacial engineering. One of the co-authors actually is Stanley Williams, who's the original Memristors guy.

• 45:26Lester Nare?

  The, the nature for, for, oh my God. What a legend.

• 45:30Krishna Choudhary?

  I thought that was a nice like, like throughput.

• 45:32Lester Nare?

  What a legend.

• 45:33Krishna Choudhary?

  Um, so Joshua Yang, who's at USC, he worked with Stanley at H, HP Labs. And then now he's a professor at, of electrical engineering at USC. So this is a collaboration between, as you said, USC Air Force Research and Kumamoto. But it's like the same lab that created the Memristors is now like just upping the game.

• 45:53Lester Nare?

  We're, we're the best. What do you want us to do?

• 45:55Krishna Choudhary?

  Which is kind of cool. Their big idea is to replace that bottom inert electrode. Instead of platinum, we're going to use graphene.

• 46:04Lester Nare?

  Okay.

• 46:04Krishna Choudhary?

  Okay.

• 46:04Lester Nare?

  This is the one that we need to be more stable.

• 46:06Krishna Choudhary?

  Yeah.

• 46:06Lester Nare?

  Doesn't want to do stuff.

• 46:08Krishna Choudhary?

  Yeah, I want it to not talk to the platinum, or sorry, I want it to not talk to the titanium. I want them to not be friends.

• 46:15Lester Nare?

  Yes.

• 46:15Krishna Choudhary?

  Platinum and titanium, they're friends at high temperature. Turns out graphene, even at high temperature, it's fine on its own.

• 46:22Lester Nare?

  I'm good.

• 46:22Krishna Choudhary?

  Yeah, it's good. And it, for, for very good reason. So graphene, it won the Nobel Prize in 2010. Um, it was isolated in 2004 by Andre Gaym and Konstantin Noiosolov, Noiosolov. Okay? They were, um, in the UK. It's a very funny story where they actually, they, they took graphite, which is the stuff in pencil lead. They put it on pieces of paper and then they got Scotch tape, put it on the piece of paper and removed it. And the physics between the Scotch tape and the graphite that's on the piece of paper would create single layers of graphite.

• 47:04Lester Nare?

  Hmm.

• 47:05Krishna Choudhary?

  Right? Single layers of carbon hexagonal shells. Graphite is a bunch of layers stacked together. Graphene is a single layer. Okay? It's, it's an incredible story because it was Scotch tape and a pencil and it won them the Nobel Prize.

• 47:21Lester Nare?

  Sometimes curiosity and just trying stuff is the key to breakthroughs that will last a lifetime. As we again have discussed multiple times on the show.

• 47:30Krishna Choudhary?

  And I mean, since then, the, we've done loads of research on how to make graphene. Obviously, like if you're trying to do industrial scale, you're not going to be doing Scotch tape and pencil, right?

• 47:40Lester Nare?

  But you wouldn't have known.

• 47:41Krishna Choudhary?

  But you wouldn't have known, right? And now people do chemical vapor deposition to make graphene. Graphene has extraordinary properties. Okay? It's the strongest material ever measured. It's an excellent electrical conductor. It's transparent. It's chemically inert. It doesn't really mess around with other things. Um, and that chemical inertness is the key property here. Side note, graphene, for the longest time.

• 48:13Krishna Choudhary?

  Was overhyped.

• 48:15Lester Nare?

  It was in Batman's suit, isn't it? Doesn't that what he uses in his suit?

• 48:18Krishna Choudhary?

  No, it's in, it's in all the movies.

• 48:20Lester Nare?

  All the movies.

• 48:21Krishna Choudhary?

  And then when you, when you go out, you're like, where is the graphene?

• 48:26Krishna Choudhary?

  Okay, it won the Nobel Prize and everything, but like, I think if you talk to a lot of material scientists, they're gonna be like, this thing was super overhyped because of those, the, it was the strongest material. It was a conductor, it was transparent, it was inert. It didn't really find a lot of chemi, like, a lot of industrial applications. So it's really nice to see that it's actually doing something. I'm sure there's gonna be people in the comments that tell me that there's all sorts of other stuff that graphene does. It's just, I haven't heard it, right?

• 48:57Lester Nare?

  And I've heard of silicon chips, I've heard of all these other things.

• 49:00Krishna Choudhary?

  Carbon nanofibers, like in F1, they use like, carbon nanofibers in the, but that's not graphene. And carbon nanofibers never won a Nobel Prize. So I'm just saying.

• 49:10Lester Nare?

  Bad PR.

• 49:11Krishna Choudhary?

  Right? Um, this, this is a totally new purpose, though. Because a lot of times, people like to use graphene for, as you said, the, the Mylar in Batman's suit, like, because it's strong, or it's like, electrically conducting. Here, we're exploiting the chemical inertness of graphene.

• 49:28Lester Nare?

  And the, and it may be finally getting its moment in, in the, in the light, because the, the implications of this, uh, could be just so enormous.

• 49:41Krishna Choudhary?

  Yeah, it really could, it really could. So let's now get into the paper, let's talk about figure one, the graphene solution. Uh, figure one A, on the top left, that is their memorister, okay? You've got a little tungsten electrode up top, you've got half-nim oxide in the middle, and you've got a graphene electrode on the bottom, okay? And that's effectively what's happening. The tungsten doesn't wanna mess with the graphene, we're gonna get into some of the cool physics about that later. On the right-hand side is what I wanna show, you see that curve, that hysteresis curve? That's characteristic of your memorister. So that is where they're showing the memorister.

• 50:24Krishna Choudhary?

  All of the colors are from, from zero degrees Celsius, all the way down to 700 degrees Celsius. And notice, the curve maintains its shape.

• 50:34Lester Nare?

  Yes.

• 50:34Krishna Choudhary?

  All the way down to 700 degrees Celsius. This is crazy.

• 50:39Lester Nare?

  Yeah, yeah, yeah, yeah.

• 50:40Krishna Choudhary?

  Right?

• 50:40Lester Nare?

  And, and because we're talking about two and a half, three X.

• 50:44Krishna Choudhary?

  Yeah.

• 50:44Lester Nare?

  The current level that we can.

• 50:46Krishna Choudhary?

  Yeah, and if you, I mean, usually in, in temperature, we always as physicists like to talk in Kelvin, right? Zero degrees Celsius is gonna be like 270, let's say 300, 300 Kelvin. 700 degrees Celsius is 1,000 Kelvin. But this is three times the thermal energy that this thing is able to withstand. Because Kelvin is really how you scale, like, how much kinetic energy is in the system, right? Like, um, at, at 1,000 Kelvin, or at 900 Kelvin, let's say, your atoms are moving with three times the kinetic energy

• 51:18Lester Nare?

  Yeah.

• 51:19Krishna Choudhary?

  as the atoms at 300 Kelvin.

• 51:21Lester Nare?

  Right.

• 51:21Krishna Choudhary?

  Okay, at room temperature. So this is, this is crazy.

• 51:24Lester Nare?

  Yeah, that's, it's, yeah.

• 51:25Krishna Choudhary?

  Yeah, on the, on the bottom left plot, you're seeing the time axis on the X-axis, right?

• 51:33Lester Nare?

  Yep.

• 51:34Krishna Choudhary?

  That's 10 to the four seconds, you're maintaining those two states of high resistance, low resistance.

• 51:42Lester Nare?

  So the cycling is maintaining.

• 51:44Krishna Choudhary?

  Yeah.

• 51:45Lester Nare?

  That we talked about, the forest is going up and down.

• 51:47Krishna Choudhary?

  Yeah, and it's fine.

• 51:48Lester Nare?

  And it's no problem.

• 51:49Krishna Choudhary?

  And it's not even coming together. It's just flat.

• 51:52Lester Nare?

  Which is, ah, right, right, right, right. Like, there's not a D, like, there, there's not a, it's not approaching the collapse.

• 51:58Krishna Choudhary?

  Yeah.

• 51:58Lester Nare?

  The, it's not approaching the, the circuit, the short circuit.

• 52:01Krishna Choudhary?

  No, it's not, yeah, short circuit would exactly mean that, like, they're both coming to the same thing. We're not seeing that at 700 degrees Celsius. This is cycling at 700 degrees Celsius.

• 52:10Lester Nare?

  So we have, it's stable.

• 52:11Krishna Choudhary?

  Yes, and on the right-hand side, we've got endurance of cycles. The X-axis there, on the bottom right, that's in log scale.

• 52:19Lester Nare?

  Holy.

• 52:19Krishna Choudhary?

  Okay, that's not a linear scale. Each of those tick marks is 10 endurance cycles, then 100, then 1,000, then 10,000, 100,000. It goes all the way up to a billion cycles.

• 52:30Lester Nare?

  Before we start to see.

• 52:32Krishna Choudhary?

  Yeah, and even then, that could just be noise, because there's, there's, there's enough, like, you know, jitter in the beginning.

• 52:37Lester Nare?

  Yeah, yeah, yeah, yeah, it's not clearly, this is incredible.

• 52:41Krishna Choudhary?

  Right?

• 52:42Lester Nare?

  Yeah, the, because what we're sort of saying, there's two things here, like, one, stability at high temperature, which is C, and then D is stability over time, which goes back to the, the two things.

• 52:54Krishna Choudhary?

  Yeah.

• 52:54Lester Nare?

  And I'm kinda getting what you were saying before about why the fundamentals of the structure impact both of these variables.

• 53:03Krishna Choudhary?

  Exactly, it's impacting both the temperature side of things, which is in the B, and the time side of things, because it's like, stable, the whole thing is stable. And actually, the next one, which is in, I think this is figure two in the paper, this shows a schematic. The, you always want a cartoon for all us stupid people like me, who are trying to understand what's going on. On the left is an old memorister, okay? Tungsten, half-nim oxide, platinum. At high temperatures, the tungsten is migrating and creating a paved highway. So the electrons will just move through that.

• 53:35Lester Nare?

  Yes, because that's the path of least resistance.

• 53:37Krishna Choudhary?

  Yeah, no, no one's gonna take the vacancies, the oxygen vacancies, why would you do that when there's a highway right next door? Um, it's like the Cars movie, you know, when the interstate was formed, nobody went through Route 66, and then your town got wrecked, right? Okay, so on the right-hand side, now, um, there's no highway, because the tungsten is trying to diffuse, but it just bounces back from the graphene. The graphene's like, I'm good, I'm all carbon, and I'm good.

• 54:05Lester Nare?

  It's, it's like, uh, California's, uh, high-speed train.

• 54:09Krishna Choudhary?

  Yeah.

• 54:09Lester Nare?

  86 miles of track, but you can't really use it.

• 54:12Krishna Choudhary?

  Yeah, you can't, yeah, no, where is it going?

• 54:13Lester Nare?

  Where is it going? Nowhere.

• 54:14Krishna Choudhary?

  Nowhere, right? And so, and so, that's exactly right, yeah. And so the, the, the tungsten is sort of just like, trying, it's still diffusing around. The atoms are still diffusing because of the high temperature, but it can't bind to the graphene. And so the only way through is with the vacancy centers that are created through that hiker's paradise.

• 54:35Lester Nare?

  Yes.

• 54:36Krishna Choudhary?

  And that's where the electrons shuttle. And so now we have exquisite control of the resistance state.

• 54:42Lester Nare?

  The, the, the one on the right here, the, the, the hiker's path that you're talking about, that structure, which is the forest, the, the bike analogy, where we have the ability to control when they're up or down, that, that, that's the point, is that, that's the lev, the lever that gives us, uh, programmatic control, for lack of a better term.

• 55:01Krishna Choudhary?

  Exactly, exactly. And Professor Joshua Wang, who is the principal investigator, he described this interface interaction between the tungsten and the graphene as oil and water. It's just like, they're, they're just not gonna mix, right? Makes sense.

• 55:14Lester Nare?

  This is so good.

• 55:16Krishna Choudhary?

  It's, it's, it's pretty cool, right? So now let's, um, you know, to get into a paper in science, you can't just have a cartoon.

• 55:22Lester Nare?

  Yeah.

• 55:23Krishna Choudhary?

  Right, that, that's for me.

• 55:26Krishna Choudhary?

  But, but, uh, in order to pub, in order to publish in science and convince your competitors that this is legit.

• 55:32Lester Nare?

  Yes.

• 55:32Krishna Choudhary?

  And all that other kinda stuff, you need actual analytical verification. So let's go to the first analytical verification. This is high-resolution transit, transmission electron microscopy. Electron microscopes, we've covered this a lot, instead of light, we're using high-energy electrons to really get down to, um, you know, tiny, tiny nanometer level resolution. On the top is a traditional memorister, okay? You can see after, after like, not a lot of time, the curves collapse.

• 56:05Lester Nare?

  Yeah.

• 56:05Krishna Choudhary?

  Right, after just like 2,000 seconds, which is like, less than an hour, um, there's no memorister.

• 56:11Lester Nare?

  It's the slope of, uh, uh, mammoth.

• 56:14Krishna Choudhary?

  Yeah, yeah, yeah, exactly.

• 56:15Lester Nare?

  Straight down.

• 56:16Krishna Choudhary?

  Yeah, yeah, chair 36, I believe. Correct me in the comments, I never go on those chairs, so that'll be you lunatics. But on the right-hand side is the transmission electron microscopes. And you can see at high temperature, you see this like mushroom cloud?

• 56:30Lester Nare?

  Yep.

• 56:30Krishna Choudhary?

  That's forming on the right-hand side? That's the platinum and the tungsten meeting up.

• 56:35Lester Nare?

  Hmm, a, a, and so instead of sort of maintaining the same, like, substrate texture or orientation, this, there's just disturbance in the force.

• 56:43Krishna Choudhary?

  Exactly, there's a.

• 56:44Lester Nare?

  You can visually see it.

• 56:45Krishna Choudhary?

  Yeah, and you can see the half-nim oxide in the middle, right? The meat?

• 56:48Lester Nare?

  Yes.

• 56:48Krishna Choudhary?

  But like, the platinum is just like going through.

• 56:50Lester Nare?

  Yeah.

• 56:50Krishna Choudhary?

  Why would you, why would you go through the half-nim oxide?

• 56:53Lester Nare?

  Yeah.

• 56:53Krishna Choudhary?

  Right, on the bottom is our new memorister with graphene. And there you can see, even at high temperature, even after all of that cycling, the graphene layer, the graphene layer is inert, the tungsten layer is inert, nothing is happening.

• 57:08Lester Nare?

  This is incredible.

• 57:09Krishna Choudhary?

  There's no chemistry happening.

• 57:10Lester Nare?

  And it's, it's also so verifiable.

• 57:12Krishna Choudhary?

  Yeah, you can literally look at it.

• 57:14Lester Nare?

  Yeah.

• 57:14Krishna Choudhary?

  Under the microscope.

• 57:15Lester Nare?

  And I can see.

• 57:16Krishna Choudhary?

  And you can see that it's happening.

• 57:18Lester Nare?

  That stupid analogy is like, imagine you have a BLT sandwich from a, a deli, and they put the, the thumb, the, the toothpick through it. In the first case, it's like, you know, the toothpick through, where you can see it disturbs the nice layers you have of your tomato, bacon, lettuce.

• 57:34Krishna Choudhary?

  Yeah.

• 57:34Lester Nare?

  And it looks like a very nice, undisturbed, but, but the point here is, is it, it, the, the the high-resolution imagery that is able to validate that this graphene-based memorister actually sustains at high temperature is undeniable.

• 57:50Krishna Choudhary?

  Yeah, yeah, yeah, it's like now you don't need a cartoon, this is the thing that the cartoon is inspired from.

• 57:55Lester Nare?

  Literally what it is, right.

• 57:55Krishna Choudhary?

  Right, like, you're just seeing it, I can see it. Um, here's another way to see it, you can use energy-dispersive X-ray spectroscopy. The idea here is that, um, like, so during, in the previous photo, we, we had transmission electron microscopy, so you're like, sending these high-energy electron beams, right? That strike the sample. Now, when those electrons strike the sample, it can transfer energy and violently kick electrons out. And when the electrons come back, they're gonna release X-rays, right?

• 58:25Lester Nare?

  Yeah.

• 58:25Krishna Choudhary?

  And if I monitor the X-rays during that electron microscopy, because every atom is unique, the X-ray signature is going to be unique. Like, in the transmission electron microscopy, people could be like, oh, like, there's some weird thing happening. How do you know that's tungsten? How do you know that's plat, platinum, right? It's just a gray image. Well, now we can tell that it is, in fact, tungsten that is leaking through, because only a certain energy comes from tungsten, and we're seeing that energy spike.

• 58:58Lester Nare?

  Yeah.

• 58:59Krishna Choudhary?

  In the old memorister, but in the new memorister, there's no tungsten spike.

• 59:03Lester Nare?

  Tungsten spike.

• 59:04Krishna Choudhary?

  The W, by the way, for those watching, W is the chemical symbol for tungsten. Because of Latin.

• 59:11Lester Nare?

  And it's so it's interesting because I think part of this is like you you're doing both of these things almost simultaneously.

• 59:17Krishna Choudhary?

  Yeah, yeah, yeah.

• 59:17Lester Nare?

  Because the the electron microscopy is triggering an event that you track with the X-ray spectroscopy. And so you're getting both the visual and the the signature.

• 59:28Krishna Choudhary?

  Yeah, exactly.

• 59:29Lester Nare?

  That allows you to identify the the composition of what you're looking at and conceive visually.

• 59:35Krishna Choudhary?

  Exactly. And so if you look in the platinum electrode, there is tungsten there. If you look at the graphene, there's no tungsten, right?

• 59:42Lester Nare?

  Undeniable.

• 59:43Krishna Choudhary?

  There were also some calculations that were done from first principles. So you've got electron densities with density functional theory. Density functional theory is something that we covered in our America 250 episode. It won the Nobel Prize. This is what I mean by density functional theory, okay? It's like you don't have to worry about every single electron. You can just be like the electron clouds are like a potential. What happens when a tungsten atom goes through? Does it bind or not? On the right hand side is what platinum looks like. These giant sort of honeycomb structures where the d orbital, which is the stuff that

• 1:00:22Krishna Choudhary?

  these are these large d orbitals of metals, right? They're extremely large. The tungsten is fine, kind of just binding to one of these d orbitals because they're so they're so big, right? And there's a lot of vacant spots where the tungsten can go and bind. On the left hand side is graphene, pristine hexagonal structure. I think it's only just like sp2 binding.

• 1:00:48Krishna Choudhary?

  Or maybe sp3. I I forget my chemistry, but in any case, the the bond lengths in between the carbons are smaller. The graphene electron clouds are a lot smaller. So the tungsten has nowhere to go.

• 1:01:02Lester Nare?

  It's incredible.

• 1:01:03Krishna Choudhary?

  Right? There's the you see the fat little like pimple?

• 1:01:06Lester Nare?

  Yes.

• 1:01:06Krishna Choudhary?

  That's the tungsten atom. And it's trying to find somewhere to bind. And it can't.

• 1:01:12Lester Nare?

  It's like the grill on like your microphone or a speaker cover.

• 1:01:15Krishna Choudhary?

  Yeah.

• 1:01:16Lester Nare?

  Versus like you described, like a bunch of donuts that got blended or like, you know, Hawaiian rolls that got baked together.

• 1:01:24Krishna Choudhary?

  Yeah, exactly.

• 1:01:24Lester Nare?

  With no clear actual like structural, you know, like a well-defined, small structural positioning.

• 1:01:30Krishna Choudhary?

  Exactly.

• 1:01:31Lester Nare?

  And it's part of your point that the the the smaller size of the electron cloud is a material aspect of why. Because the tungsten is just not small enough to.

• 1:01:42Krishna Choudhary?

  Yeah, yeah, the tungsten is not small enough. The smaller size also means that you need a higher energy to get in there.

• 1:01:47Lester Nare?

  That makes sense.

• 1:01:47Krishna Choudhary?

  Right?

• 1:01:47Lester Nare?

  Yeah.

• 1:01:48Krishna Choudhary?

  And and and all of the stuff is is taken.

• 1:01:51Lester Nare?

  Yes.

• 1:01:51Krishna Choudhary?

  Right? With with graphene, because of the hexagonal structure, it's just carbon on carbon on carbon.

• 1:01:55Lester Nare?

  There's no.

• 1:01:55Krishna Choudhary?

  All of the carbon atoms are happy. They don't want anything else.

• 1:01:58Lester Nare?

  They don't want anything.

• 1:01:59Krishna Choudhary?

  Right?

• 1:02:00Lester Nare?

  Yeah. And all, oh, that's so good.

• 1:02:02Krishna Choudhary?

  So it's all coming together. And the final thing that I want to talk about is the nudged elastic band. This isn't the final thing, but I just go go I'm going through their figures because they're just so cool. Okay, so on the left hand side, again, that's the old memorister.

• 1:02:18Krishna Choudhary?

  This is an activation energy diagram that shows if I want the tungsten to bind to my platinum, I need to go over this hill. And then and then there's like a valley on the other side where I'm bound to the platinum. The height of the hill is point three electron volts. And then the the there's a there's a nice valley where I can just like sit. On the right hand side is the same diagram, but for graphene, the height of the hill is now one to two electron volts. And there's no nice valley, right? Like if I'm up there and I'm jiggling around, I'll just come right back.

• 1:02:52Lester Nare?

  Yeah.

• 1:02:53Krishna Choudhary?

  To my original state.

• 1:02:54Lester Nare?

  Yeah.

• 1:02:54Krishna Choudhary?

  So again, same idea. It's really hard to bind to graphene.

• 1:03:00Lester Nare?

  It's really good.

• 1:03:00Krishna Choudhary?

  Okay. Now, one thing that I was thinking about was there's kind of a paradox in my head, right? Like the high resistance state makes sense. High resistance, meaning

• 1:03:12Krishna Choudhary?

  there's no oxygen vacancy highway. And so

• 1:03:19Krishna Choudhary?

  like my electrons aren't going through, but everything is kind of inert, right? Now, let's say I have oxygen vacancy highway in that low resistance state. What prevents the oxygen vacancy highway from moving around?

• 1:03:34Lester Nare?

  Yeah.

• 1:03:35Krishna Choudhary?

  At high temperature.

• 1:03:36Lester Nare?

  Yeah.

• 1:03:36Krishna Choudhary?

  Right? At high temperature, if I've got these like vacancy lines where the electrons are going through, but those vacancies can move, as I was saying.

• 1:03:44Lester Nare?

  As we talked about earlier, they're not stationary.

• 1:03:46Krishna Choudhary?

  They're not stationary.

• 1:03:47Lester Nare?

  They're not fixed.

• 1:03:47Krishna Choudhary?

  Yeah, yeah, yeah. So what's preventing those guys from moving around at high temperature when there's all this jiggle? It has to do with something called phase separation. There was a paper about this where the system reaches thermodynamic flux equilibrium where there's a net migration of zero, meaning that the material separates into an oxygen-rich insulating phase and then an oxygen-poor conducting phase. And it's that same argument about oil and water. There's going to be parts of the hafnium oxide that have a lot of these oxygen vacancies. And then there's going to be parts that don't. And those guys don't want to mix together.

• 1:04:23Lester Nare?

  They don't want to mix.

• 1:04:23Krishna Choudhary?

  Because they become like oil and water. Now, how can we tell in our new memorister? Well, they did electron energy loss spectroscopy, which is similar to the X-ray stuff that I was talking about. Like the electrons are now coming out and then we measure the the energy of the electrons. The main thing that I want you to see is in the low resistance state, which is on the bottom. So the the color tells you how much oxygen vacancy there is. The darker it is, the more oxygen vacancy there is. So that's why the low resistance state at the bottom, that has it's kind of darker because there's a lot more oxygen vacancies. The the key thing that I want you to notice is on the bottom, we're plotting the number

• 1:05:07Krishna Choudhary?

  of oxygen vacancies as a function of space. Like we're going, we're moving along in nanometer position. We're moving along our memorister and we're plotting how much oxygen vacancy there is. If you if you expect a lot of mixing, it should be at equilibrium. But if there's not a lot of mixing, there should be clumps.

• 1:05:26Lester Nare?

  Yeah.

• 1:05:26Krishna Choudhary?

  Where there's a lot of oxygen vacancy and then not a lot of oxygen vacancy.

• 1:05:29Lester Nare?

  Because of this oil and oil and water you just talked about.

• 1:05:31Krishna Choudhary?

  And that's what we're seeing. We're seeing a very bumpy profile, right? There's certain spots where there's a lot of oxygen vacancy and then other spots that there aren't. If this stuff mixed, it would look like the middle plot in that high resistance state. Right?

• 1:05:46Lester Nare?

  Yes.

• 1:05:47Krishna Choudhary?

  But because it's not mixing, you get this valley and mountain landscape.

• 1:05:52Lester Nare?

  And so part of what we're saying is there's two dynamics here. There's both the dynamic between the how the tungsten and the graphene relate. And then the the how how fight oxygen?

• 1:06:04Krishna Choudhary?

  Yeah, um, hafnium.

• 1:06:05Lester Nare?

  Hafnium oxide. Hafnium oxide in the middle also has dynamics that not that are that combined with the relationship between the tungsten and the graphene such that the graphene doesn't want to create the highway. And the oxide in the middle also doesn't allow movement.

• 1:06:27Krishna Choudhary?

  Yeah.

• 1:06:27Lester Nare?

  And so both of these things combined are are meaningful for the impact in terms of from an industrial or performance perspective.

• 1:06:35Krishna Choudhary?

  Exactly.

• 1:06:36Lester Nare?

  And it's both things, not just the ends, the ends of the sandwich.

• 1:06:40Krishna Choudhary?

  Exactly. Yeah. So both the high resistance state, which is the one that can or sorry, no, the high resistance is the zero. Because that's like the the electrons aren't moving. And then the low resistance state where there is current, that's the one. Both of those are now stable.

• 1:06:53Lester Nare?

  Right.

• 1:06:53Krishna Choudhary?

  Right?

• 1:06:54Lester Nare?

  For for dynamics that we just walked through. Which is which is which is an important point because I was going to end up asking, but what about the middle stuff?

• 1:07:03Krishna Choudhary?

  Yeah. Yeah. The middle stuff is also oil and water.

• 1:07:06Lester Nare?

  Right, right, right.

• 1:07:07Krishna Choudhary?

  It's kind of cool.

• 1:07:08Lester Nare?

  Yeah.

• 1:07:08Krishna Choudhary?

  And they did a lot of benchmarking of like, okay, what what is all the state of the art and then where is this? And it's kind of crazy. The retention, which is how how long it takes and the temperature, that's part A. You want it to be high temperature, high retention. So you've got a desired corner that's the shaded and there's a star where the current work is and all of the other riffraff.

• 1:07:32Lester Nare?

  This is not even.

• 1:07:33Krishna Choudhary?

  Is not even close. You've got the writing endurance in B versus temperature. Again, the only star in the desired corner is this work. See the on off ratio versus the temperature, desired corner is us. The spider web diagram. The yellow is the current work and it's always larger.

• 1:07:55Lester Nare?

  Yeah, right.

• 1:07:56Krishna Choudhary?

  In temperature, in retention, in endurance, in the device size, all sorts of stuff. Now, there is a little bit of Photoshopery happening here, right? Because I could easily make the desired corner like elsewhere. But but in any case, it's in the by every metric, it's always in it's the most in that corner. So whatever desired corner you made, it would always be the most.

• 1:08:20Lester Nare?

  Yeah, right.

• 1:08:21Krishna Choudhary?

  Out there.

• 1:08:21Lester Nare?

  Right.

• 1:08:21Krishna Choudhary?

  Right?

• 1:08:22Lester Nare?

  It's the closest to the optimal regardless of whether you made the desired smaller or larger, whatever.

• 1:08:28Krishna Choudhary?

  Yeah, yeah, yeah. But a game recognized game because like I've done that.

• 1:08:32Lester Nare?

  I know what you're up to.

• 1:08:33Krishna Choudhary?

  Yeah, I'm going to make the square right here so that all the others.

• 1:08:37Lester Nare?

  Are out, but like buy it.

• 1:08:40Krishna Choudhary?

  Yeah, but in this case, I think it's like fairly obvious and I don't think they're doing any shenanigans. I just thought that was kind of funny as a plot. And finally, like to because I think they knew that people would call BS.

• 1:08:52Lester Nare?

  Right.

• 1:08:52Krishna Choudhary?

  So they took a video of their lab.

• 1:08:56Lester Nare?

  They're like proof.

• 1:08:56Krishna Choudhary?

  They're like, this is proof. And the and the thingy shows, oh, 700 degrees Celsius. And they've got their they've got like a computer with their with the two electrodes on the on the two on the titanium and the graphene. And they're measuring the on off ratio and they're measuring the histories curve. And here you can see the histories curve like, okay, I turned the voltage up, I turned the voltage down, I'm getting this histories, guys. This is happening in real time. I'm not making this stuff up. Like, I think it's really cool that like this is part of the supplement on the science website. Because like whenever you publish, right? There's the main figures and the main text. And then you provide supplementary data and supplementary figures.

• 1:09:40Krishna Choudhary?

  A lot of the figures that we've seen here in today's episode are from the supplement. And this is a supplementary video that they show. Okay, guys, here's my histories curve. It's definitely a memorister. This is happening at 700 degrees Celsius and it's definitely working.

• 1:09:57Lester Nare?

  Picks or didn't happen?

• 1:09:58Krishna Choudhary?

  Yeah.

• 1:10:00Lester Nare?

  In

• 1:10:02Lester Nare?

  frontier science research. But it's also kind of like, I think one people, one thing, you know, as we always talk about is scientists are some of the most skeptical people, especially when it's other people that say they did something.

• 1:10:15Krishna Choudhary?

  It's like, why didn't I think of that?

• 1:10:17Lester Nare?

  I don't I don't believe you.

• 1:10:19Krishna Choudhary?

  Yeah. But here, yeah, it's like, okay, here, 704 degrees Celsius, guys. There's my thermometer.

• 1:10:26Lester Nare?

  God, this is so good because, you know, and I think you've done a good job of walking us through to kind of understand that there's a fundamental insight that happens that then you you take to the end of possibility or the end of kind of the story in order to get to something that's practical. And it was a very, it was maybe subtle for folks who are material scientists and who work in the space. But if you're not in this lane, it can seem like, oh, this is a subtle point. That has such huge implications. And they've used graphene as the other part of this layer here.

• 1:11:09Lester Nare?

  Are there other things?

• 1:11:10Krishna Choudhary?

  Yeah.

• 1:11:11Lester Nare?

  That have different performance characteristics.

• 1:11:14Krishna Choudhary?

  Yeah, maybe we can now start, maybe we can now start replacing the tungsten. I don't know.

• 1:11:20Lester Nare?

  Right. And then, and then what does that do?

• 1:11:22Krishna Choudhary?

  Yeah, it just, it opens up all sorts of possibilities.

• 1:11:24Lester Nare?

  Right.

• 1:11:25Krishna Choudhary?

  So now let's talk about the future. Okay, what would this current research have to do with how we move forward in computation as a society? We've talked about the von Neumann bottleneck for a long time. This is the tyranny of the processor having to be separate from our memory. Modern architectures waste a lot of power and time trying to move data between our CPU, which is where all of the computation is happening, and the RAM, which is where the data and the memory is stored. This was, von Neumann came up with this, and it's the bedrock of almost all of the computation that we have in our society today. Now with neural networks, this is especially bad because you've got to load the weights.

• 1:12:11Krishna Choudhary?

  And then you've got to do the computation. Then you've got to load a new set of weights. So you got to dump the old weights, right? And all of this takes a lot of time. It takes a lot of energy, dissipates heat. And what exactly is the computation that happens in these AI systems? When you've got a neural network, what we're really doing fundamentally is we're relying on matrix times vector multiplication. The vector is your state and the matrix is the weights of your network. You multiply the matrix, you multiply the matrix to the vector, and then you get a new vector that tells you how the state is changing. At the end of the whole thing, you get a giant vector in the example of L L Ms.

• 1:12:53Krishna Choudhary?

  You have a giant vector with all of the next possible tokens. And you pick usually the one with the highest probability. Okay, how does matrix multiplication work? How do you multiply a matrix by a vector? For those from linear algebra, you already know this, but let's just do a little bit of a review. Okay, let's say I've got a three by three matrix. On the left there, I've got one, one, two, two, one, three, one, four, two. And I want to multiply it by a vector, three, one, two, three, one, two is the vector. That's my state of like next tokens, let's say. And the matrix tells us how to change that vector to create a new probability vector with the new tokens. Okay, what you do is you go row by row and you take each row, you multiply it by the vector.

• 1:13:38Krishna Choudhary?

  So the one gets multiplied by the three, the one gets multiplied by the one, two gets multiplied by the two, and you add it all up. That's your first row. Then you go to the second row, add it all up, third row, multiply, add it all up, and you get your new vector. Okay, that's fundamentally what most of the AI computation that we all know and love, I guess, that's what that is. Okay, that's what's happening.

• 1:14:05Lester Nare?

  Keyword, I guess.

• 1:14:06Krishna Choudhary?

  Yeah, that's what's happening. Now, we'd like to do better. We'd like to not load the weights every single time in order to do this computation.

• 1:14:18Lester Nare?

  And this is part of the reason why, for example, the cloud versus local with AI models and stuff. It's why if you want to do it locally, you need a very powerful machine because it has to do this.

• 1:14:28Krishna Choudhary?

  Yeah, it has to store all of those matrices and it's got to do all of that computation. That's why GPUs are so important because GPUs are just insanely good at matrix multiplication.

• 1:14:39Lester Nare?

  That's specific.

• 1:14:40Krishna Choudhary?

  At that very specific task. Okay, they're not good at like doing normal emails. But it turns out Nvidia made the big gamble way back in the day that actually graphics, which is matrix multiplication,

• 1:14:57Krishna Choudhary?

  is going to have a use for later. And it turns out, yeah.

• 1:15:00Lester Nare?

  And things other than video games. For those who are gamers, we've been very familiar with GPUs for a while. And now everyone is making custom PC builds unnecessarily expensive.

• 1:15:09Krishna Choudhary?

  Yeah, yeah, exactly. So instead of doing all this von Neumann nonsense, in instead, we can do something called in memory computing. In memory computing, meaning I don't have to move anything. Okay, we can use something like a resistor to

• 1:15:28Krishna Choudhary?

  do the computation without changing anything. So again, let's talk about how that would work. I told you about how matrix multiplication works, right? Like matrices, you multiply it by a vector and then you get a new vector. Well, now, what if we had the old vector come in like wires? Okay, and this is what we see at the, on the, on the right. And let me, let me see if I can say this correctly. Okay, so I've got a matrix and I've got an old vector and I want to make a new vector. And the way that I do that is the rows get multiplied to each of them and then I get added up, right? I can use the rules of electronics, V equals I R and the summing of voltages and the summing of currents to then just do that using physics. Here's what I do.

• 1:16:13Krishna Choudhary?

  My old vector is represented by the old, by currents that are going at the very top. The old voltages, I should say. They're, they're, each of the wires at the very top is held at a certain voltage, right? I've got resistors that are attached to these voltages. And then I've got a new set of wires at the bottom. Because of electronics, the new current, it's a new set of currents at the bottom. Because of electronics, right? The new currents are going to be related to the voltage at the top and the resistance in between. And all I have to do is add up the currents.

• 1:16:56Lester Nare?

  I'm so mad.

• 1:16:57Krishna Choudhary?

  Right? In this case, it's not really resistance, it's one over resistance. It's the, it's the conductance and the, and then the current is just voltage multiplied by conductance. But it's the same thing. It's just V equals I R the other way around. And all we're doing is using the physics in place, right? We don't have to move weights around as long as the weights are the same. I can use the physics to be like voltage multiplied by conductance gives me a current. Voltage multiplied by another conductance gets, gives me another current. And so my new vector is going to be the sum of all of those currents. And there you go. Matrix multiplication using physics.

• 1:17:35Lester Nare?

  I'm so, I'm so mad. That's so, that's so.

• 1:17:38Krishna Choudhary?

  It's so good.

• 1:17:38Lester Nare?

  It's so good. And the part of the point here is then, then you can get around the von Neumann bottleneck as a result of that because you're not having to transition between your compute layer and your memory layer.

• 1:17:48Krishna Choudhary?

  Yeah, and all you have to do is the weights have to be programmed into the conductance. The input is the voltage and the resulting multiplication comes out as current. I'm just using Ohm's law and Kirchoff's junction rules, the stuff that you learn in like intro physics. Right? Now, are we capable of doing something like this? Well, this particular paper itself made a thirty two by thirty two analog resistance state. And it works at thirteen hundred degrees Fahrenheit. It works at low voltage, zero point five volts is all you need.

• 1:18:21Krishna Choudhary?

  Thirty nanoseconds switching in the speed. And it definitely, it, it, it proves that you can be fully capable of storing complex, multi-level analog neural weights for whatever AI interface that you're working with. It can do it in extreme environments, thirteen hundred degrees Fahrenheit. And the standard digital GPU, which relies on all these transistors and the CMOS and all that other kind of stuff. The, the traditional GPU is going to get fried. But if I use this memorister where the, the conductances, the weights are stored using this memorister, now all of a sudden, I've got something that can actually work.

• 1:18:59Lester Nare?

  Golly, it's so, it's so good. And it, it's this interesting combination of both things, which is the fundamental discovery around the memorister construction for high temperature plus the concept of in memory computing together.

• 1:19:22Krishna Choudhary?

  Yeah.

• 1:19:24Lester Nare?

  It, it, there's a, because it's, it's not just one or the other. Both things give you now the single chip. That can work in high temperature, that can, you know, run comparatively for a long time.

• 1:19:38Krishna Choudhary?

  Faster.

• 1:19:39Lester Nare?

  Faster. And can do both your compute and memory at the same time.

• 1:19:44Krishna Choudhary?

  Exactly. And of course, the authors have made a startup.

• 1:19:49Lester Nare?

  Of course.

• 1:19:50Krishna Choudhary?

  There's a startup called Tetra Mem. It was co-founded by Joshua Yang, who's the P I of the paper that we're talking about, along with Chang Fei She and the other authors.

• 1:20:00Krishna Choudhary?

  And it's already working to commercialize this crossbar memorister device to replace power-hungry GPUs, right?

• 1:20:07Lester Nare?

  They're getting acquired immediately.

• 1:20:09Krishna Choudhary?

  Yeah, no, especially with this.

• 1:20:11Lester Nare?

  Immediately.

• 1:20:12Krishna Choudhary?

  Now, let's talk about what this has to do with data centers in space.

• 1:20:16Lester Nare?

  Okay.

• 1:20:16Krishna Choudhary?

  Okay. Elon wants to put data centers in space. Why? Because it's probably possible. And I mean, it helps SpaceX, obviously. And it's not just SpaceX that's trying to do this, right? Google is trying to do this. There's a bunch of startups that are trying to do this. And it's looked impossible for a very, very long time because of a sort of fundamental physics quandary. The reason why is because these GPUs are highly reliant on cooling mechanisms. Because the GPUs can't withstand a lot of heat. That's why whenever you hear about like all these data centers taking up local water, the water is being used to cool down the GPUs effectively.

• 1:21:00Krishna Choudhary?

  At the end of the day, that's most of the water being used is just to extract heat from these GPUs and put it out into the environment. That's why the data centers, the climate around the data centers, there's like a microclimate that's created and the temperature gets raised. And then all the environmental people are like, okay, what's happening to flora and fauna? Which is completely reasonable, right? I don't want to hurt like the planet and especially the planet that's right around those data centers. So, let's talk about how heat transfer happens. There's three types of heat transfer, okay? There's convection, conduction, and radiation. Convection is hot stuff moves around to the cold part.

• 1:21:40Krishna Choudhary?

  And then the cold part goes down to where the hot stuff is. That's how, like, if you put a pot on a stove, the water gets heated uniformly because the hot packets are moving and the cold packets are moving. So that's convection. Conduction is the atoms themselves jiggling around to conduct heat from one spot to the other. That's why the handle gets hot. And then finally, the most inefficient part is radiation, which is literally photons coming out. Like, the reason why a fire is hot, but if you put your hand in front of the fire, all of a sudden you don't feel that hot is because you've stopped photons from getting to your face, okay?

• 1:22:22Krishna Choudhary?

  And that's why like when a shade is so important, because now the photons, the infrared photons from the sun are not hitting you. And then all of a sudden, you feel like 10 or 20 degrees cooler. You're right next to the sun, right? The shade is only shading your part. But the reason why it's so effective is because the photons aren't getting to you. The convection and the conduction still is, right? The hot pockets of air are still moving towards you, but the photons are not. Okay, so those are the three types of heat transfer. Now, terrestrial data centers, they mostly use the first two. Mostly it's convection. That's why you've got water pipes going through, because the water gets hot and then you move the water to a colder spot.

• 1:23:04Krishna Choudhary?

  It dumps the heat and you cycle it back and so on and so forth, right?

• 1:23:10Krishna Choudhary?

  Terrestrial data centers have issues, right? Where's the power gonna come from? Where's the water gonna come from? Who's gonna build it?

• 1:23:17Lester Nare?

  Yeah, who's gonna pay for it?

• 1:23:18Krishna Choudhary?

  Yeah, there's a lot of nimbyness going on. And in this case, the nimbyness is a good thing, right? We don't want, I don't want data centers in my neighborhood.

• 1:23:26Lester Nare?

  Yeah.

• 1:23:26Krishna Choudhary?

  Okay. I might want the AI, but I really don't want the data centers, right? And so that's why people are looking into space. Now, people have already started looking. This is StarCloud. It's a startup that's backed by Nvidia. Google is doing its own thing. And there's a lot of smart people betting on this thing. Here it shows a five gigawatt data center.

• 1:23:46Lester Nare?

  Crazy.

• 1:23:47Krishna Choudhary?

  But the radiator that you would need to dissipate all that heat with radiation is something like a four kilometer square.

• 1:23:55Lester Nare?

  And you have real, you know, getting any payload into space is cost prohibitive.

• 1:24:02Krishna Choudhary?

  Yeah.

• 1:24:03Lester Nare?

  And so getting a payload that's four kilometers by four kilometers wide will take a modular system, multiple launches. Yes, the cost of launches is going down.

• 1:24:11Krishna Choudhary?

  Yeah. But still, it's four kilometers worth of.

• 1:24:14Lester Nare?

  Stuff.

• 1:24:15Krishna Choudhary?

  Worth of stuff, right?

• 1:24:16Lester Nare?

  It's not a joke.

• 1:24:17Krishna Choudhary?

  It's not trivial, right? And there's several important papers that are coming out trying to plan for this kind of thing. Like, how do we develop carbon-neutral data centers in space? I want to highlight this because this is in Nature Electronics. This is a top journal. It's not impossible. There's a lot of rhetoric out there that's saying that data centers in space is impossible because of the vacuum of space and people need to take undergraduate physics. It's not true.

• 1:24:42Lester Nare?

  Right.

• 1:24:42Krishna Choudhary?

  Okay? It's hard, but that's a key distinction from it's impossible, okay? We, I mean, we obviously do it, right? The International Space Station is already doing this. If we look at a photo of the International Space Station, the curved panels that we see, those are solar panels that are facing the sun. The, the flat ones, those are radiators. Those are radiating out heat into space. So that the astronauts that are on board don't get cooked alive and all of the electronics that is, you know, doing computation. There's several computers up there. Those don't get cooked alive. The way that works is using both convection and radiation. So you've got convection in that they use ammonia instead of water, because ammonia has a low freezing point.

• 1:25:27Krishna Choudhary?

  If you use water, then the water's just gonna freeze when it gets to the radiator. And then like what? So, so, so that's why you use ammonia. The ammonia uses convection to take the heat to the radiator. And then the radiator takes that heat and radiates it out into space, okay? Now, what we want to do is make this thing cheaper. And that is perhaps an engineering problem, especially in the context of the paper that we've just covered. I'd like to, I'd like to pose that as a challenge and then see if we can work through with just some like first principles back of the envelope thinking, okay? The technology poses three advantages. One, let's talk about the physics of thermal radiation.

• 1:26:10Krishna Choudhary?

  The reason why everyone's saying that it's gonna be impossible, right?

• 1:26:16Krishna Choudhary?

  Thermal radiation is governed by something called the Stefan Boltzmann law, which states that the energy that is radiated by a surface at a certain temperature is proportional to the fourth power of that temperature. This is why it's hard, okay? It's not T squared, it's T to the fourth. So if I double the temperature, I'm increasing the amount of power output I need, or the power output that's going, going out

• 1:26:41Krishna Choudhary?

  by a factor of 16, okay? Now, this is actually a good thing, okay, in the context of this current paper. Now, standard silicon processors, they've got to be relatively cool to prevent failure, right? But you can only allow that chip with the standard silicon

• 1:26:58Krishna Choudhary?

  to run at like tops 100 degrees Celsius. At 100 degrees Celsius, right, let's say 400 Kelvin is the tops that you can do.

• 1:27:10Krishna Choudhary?

  At 400 Kelvin, the amount of radiation that I'm letting off is gonna be some amount. Some amount of photons are going off. Now, what if I could make that go up to 700 degrees Celsius, 1,000 Kelvin? So I've effectively doubled the temperature that I'm working with. Well, the number of photons, the amount of power that I'm dissipating has now gone up by a 16, by a factor of 16. If the amount of power per unit area has gone up by a factor of 16, then in order to dissipate the same amount of power, I only need a 16th the size of radiator.

• 1:27:47Lester Nare?

  Yeah.

• 1:27:49Krishna Choudhary?

  Yes?

• 1:27:49Lester Nare?

  Yeah.

• 1:27:49Krishna Choudhary?

  The size of the radiator goes down the higher the temperature that you can operate. And this is crucial for putting the stuff into space, right? Because of what you said, it's, it's hard to put stuff in space.

• 1:28:02Lester Nare?

  Yes.

• 1:28:03Krishna Choudhary?

  It's hard, it's expensive. I'd like to put less stuff in space. This could be the key, right? Because now I can operate things at a much higher temperature, meaning that the amount of watts that are going out as radiation into space is higher, which means the amount of area that I need for my radiator is smaller.

• 1:28:22Lester Nare?

  This is so interesting. And it is, it is enabled by this high-temperature Memristors and the fundamentals that we just walked through that, again, now give you a different substrate, a whole different computing paradigm when you think about the concept of a data center in space.

• 1:28:40Krishna Choudhary?

  Yeah, exactly. And I did some back-of-the-envelope calculations, right? So, let's, let's say I need a radiator for a one-megawatt space server, okay? That means one megawatt of electricity is coming in from my solar panels. Okay, now at standard 30 degrees Celsius, so that's 300 Kelvin, if I want to dump one megawatt of heat, I would need 2,000 meters squared. That's eight tennis courts.

• 1:29:08Krishna Choudhary?

  And I want to dump just as much energy that's coming in, right? Because if I don't dump the energy that's coming in, then my temperature increases. And then the electronics are not stable. My satellite keeps increasing in temperature. So whatever energy is coming in, I'd like to dump out. So one megawatts in, one megawatts out. The what matters is the temperature that I'm operating at. Okay. Now, if one megawatt is coming in, and now let's say I'm operating at 300 degrees Celsius. That's around 600 Kelvin ish. My area has gone down to 150 meters squared. I've gone from 2,000 meters squared to 150 meters squared. That's a reduction of 90%. Right? If I go even further, because this thing was at 700 degrees Celsius, right?

• 1:29:51Krishna Choudhary?

  If I go even further to 600 degrees Celsius now, meaning 900 Kelvin. Now, my radiators only need to be 30 meters squared. And that's totally doable.

• 1:30:03Lester Nare?

  That's very reasonable.

• 1:30:04Krishna Choudhary?

  Right? That's that's already in the ballpark of stuff that we've already put out there.

• 1:30:08Lester Nare?

  Right, right. Right, right. That's so fat. It's it's for me, it's a little counterintuitive where it's at the higher, you know, when you before we started. The higher the temperature, the less surface area you need to dissipate. The heat, it doesn't feel.

• 1:30:22Krishna Choudhary?

  Yeah, as long as the stuff is not cooking.

• 1:30:25Lester Nare?

  Right.

• 1:30:25Krishna Choudhary?

  Right? But like, it kind of makes sense because um, like, if you think about like, you know, those like electric stoves with the coils?

• 1:30:32Lester Nare?

  Yeah.

• 1:30:33Krishna Choudhary?

  Right? The the higher the temperature, the more the more heat is coming out. That's the whole point of how it cooks stuff.

• 1:30:39Lester Nare?

  No.

• 1:30:40Krishna Choudhary?

  Right? I mean, no, I guess that's not true because there's like contact, but you get what I'm saying, right? Like, if you're around that thing.

• 1:30:45Lester Nare?

  I know what you mean.

• 1:30:46Krishna Choudhary?

  It's like, there's, there's a lot more photons that are coming out. So you're dumping a lot more energy. And as long as you can live in at 700 degrees Celsius, you're good to go.

• 1:30:55Lester Nare?

  And it's just because we've never been able to think about it because we've never been able to operate. Yeah, there's. That temperature level. So it's never was even a possibility.

• 1:31:02Krishna Choudhary?

  There were no chip components that could withstand that temperature. So everyone was doing these calculations at the lower temperature, being like, oh, I need tennis court sized, four kilometers squared size. But now I've reduced stuff down to like 95, 99% the area, just because my components can withstand the higher temperature. My components, my computer can be hotter. And so the amount of radiator I need is a lot, lot lower by T to the fourth.

• 1:31:29Lester Nare?

  This is so, I mean, you know, again, there is the industrial scale question and all of these other, you know, engineering. But but to the point you brought up earlier, a lot of the narrative and rhetoric has been dismissive on its face in a way that doesn't even take into account what we're doing at the frontier. Yeah, I mean, this paper came out in March.

• 1:31:54Krishna Choudhary?

  Yeah.

• 1:31:55Lester Nare?

  By the way, and this discussion about data centers in space has really heated up as we've gotten into the summer.

• 1:32:00Krishna Choudhary?

  Yes.

• 1:32:00Lester Nare?

  Uh, which was after this paper had come out. And most of the folks who have been like, it's impossible. You know, certainly one from a fundamental physics perspective.

• 1:32:10Krishna Choudhary?

  It's not impossible.

• 1:32:11Lester Nare?

  It's not impossible. And then also from where we are on the frontier, both from a basic research and an engineering perspective. It's a very different paradigm than, you know, just talking about putting the same thing we have in a data center on the ground.

• 1:32:23Krishna Choudhary?

  Yeah.

• 1:32:23Lester Nare?

  And just putting it in space.

• 1:32:24Krishna Choudhary?

  Exactly. And if you combine that with the fact that payloads to space are going to get cheaper, as you said, the amount of payload that I need is going to go down.

• 1:32:33Lester Nare?

  Yeah.

• 1:32:34Krishna Choudhary?

  This is totally a doable thing.

• 1:32:35Lester Nare?

  Right.

• 1:32:36Krishna Choudhary?

  Right? As long as we keep innovating and we keep going through with high temperature Memristors, high temperature memory, high temperature computation. That's going to be the key, I think.

• 1:32:46Lester Nare?

  Yeah.

• 1:32:46Krishna Choudhary?

  To unlocking data centers in space.

• 1:32:48Lester Nare?

  Yeah, yeah, because you can have a lot more smaller, you'd have, you know, much smaller space servers. With high output capability. Meaning we're not going to be, you know, looking up at the night sky and seeing, you know.

• 1:33:06Krishna Choudhary?

  Yeah.

• 1:33:07Lester Nare?

  These giant floating radiators.

• 1:33:09Krishna Choudhary?

  Yeah. And and I, I mean, it perhaps is is is going to be bad for astronomy, terrestrial astronomy. But there's, there's got to be ways around it. I mean, it's already bad with the Starlink satellites that are up. But does that mean that like, we don't provide internet to like these remote areas? Like, you know, technology and innovation comes at a cost and we're just going to have to figure out ways to battle.

• 1:33:32Lester Nare?

  And with the lower cost of payload, you could argue we could have a much larger array of space based instrumentation.

• 1:33:38Krishna Choudhary?

  Exactly.

• 1:33:39Lester Nare?

  That exists that negates the need to have terrestrial.

• 1:33:42Krishna Choudhary?

  Yeah.

• 1:33:43Lester Nare?

  Observatories. Again, there's some caveats there.

• 1:33:45Krishna Choudhary?

  Yeah, yeah.

• 1:33:46Lester Nare?

  There's a lot of caveats.

• 1:33:47Krishna Choudhary?

  A lot of caveats, right?

• 1:33:48Lester Nare?

  But, but, you know, there are trade offs and we'll have to continue to figure out.

• 1:33:51Krishna Choudhary?

  Maybe we can make the orbits like avoid Chile, which is where like half of everything is.

• 1:33:56Lester Nare?

  Right.

• 1:33:56Krishna Choudhary?

  Right? If you just avoid like Hawaii and Chile, like.

• 1:33:59Lester Nare?

  No fly zones.

• 1:34:00Krishna Choudhary?

  Half of the astronomers are going to be happy.

• 1:34:02Lester Nare?

  Yeah, right.

• 1:34:02Krishna Choudhary?

  You know? So um, I mean, that's going to be hard, given that it's like high Earth orbit and whatever. But in any case, the the other thing that I want to bring up is this is not just an advantage in terms of cooling. Okay? There's two other things that this new memorister technology would give us.

• 1:34:20Lester Nare?

  Okay.

• 1:34:20Krishna Choudhary?

  For data centers in space. One is the extreme power efficiency. I was talking about how it only takes like very little amount of voltage in order to do that computation with a memorister. Now, satellites operate on extremely strict power budgets, you can imagine, right? Often it's under 20 watts. And in standard AI chips, nearly every single watt of electricity is consumed directly into heat. But Memristors use this in memory analog computing. They don't have to do this von Neumann bottleneck.

• 1:34:50Lester Nare?

  Right.

• 1:34:50Krishna Choudhary?

  Right? So if we're applying Memristors here, then that complex mathematics instantaneously happens without shuttling the data back and forth. Now you're consuming a fraction of the power of a traditional GPU. And that's going to bring down the amount of power that you need to dissipate again.

• 1:35:08Lester Nare?

  So this is both, you can have the radiators be smaller and you can have the solar panels be smaller.

• 1:35:12Krishna Choudhary?

  Exactly.

• 1:35:13Lester Nare?

  Because you don't need as much power intake.

• 1:35:15Krishna Choudhary?

  Exactly. Or with the same solar panels, you can do a lot more.

• 1:35:18Lester Nare?

  Right.

• 1:35:18Krishna Choudhary?

  You know, either way.

• 1:35:19Lester Nare?

  Right, right.

• 1:35:20Krishna Choudhary?

  Efficiency is always great.

• 1:35:21Lester Nare?

  Yeah, yeah.

• 1:35:22Krishna Choudhary?

  Both in power dissipation and in terms of computing. And finally, the other big thing that people talk about with data centers in space is like, normal GPUs, a cosmic ray comes in.

• 1:35:32Lester Nare?

  Yeah.

• 1:35:33Krishna Choudhary?

  I don't know where that, what if that bit was a zero or a one, right? Like, what? So like a nor a galaxy decided to fart.

• 1:35:41Lester Nare?

  Yeah.

• 1:35:42Krishna Choudhary?

  And then, and then now like my AI query is giving me nonsense.

• 1:35:46Lester Nare?

  Right.

• 1:35:46Krishna Choudhary?

  That's not great.

• 1:35:47Lester Nare?

  Right.

• 1:35:47Krishna Choudhary?

  Right? You need electronics that is able to sustain performance in a high radiation environment.

• 1:35:54Lester Nare?

  Yeah.

• 1:35:54Krishna Choudhary?

  Memristors are great for this because Memristors store memory by physically moving atoms and creating structural bridges, right? This like valence charge mechanism.

• 1:36:04Lester Nare?

  Yeah.

• 1:36:04Krishna Choudhary?

  Rather than relying on these easily disrupted pockets of electrical charge. So now you can imagine a cosmic ray comes in. It's not really going to upset the valence charge mechanism all that much compared to if there was a single, like, sort of point of failure.

• 1:36:20Lester Nare?

  Right. And and and so the, there is the, we have a thermal radiation benefit. A power efficiency benefit and a resilience benefit. And it's hard for me to imagine, again, there is the engineering problem. But it's kind of like when Nvidia started with GPUs before you could really understand what the impact would be. We already can see now, in the case of data centers in space, why, if you can figure out the industrial scaling of this. It it it makes the execution of it in three, the three arguably, three of the most important categories.

• 1:37:02Krishna Choudhary?

  Yeah.

• 1:37:02Lester Nare?

  That you care about as an operator significantly better.

• 1:37:08Krishna Choudhary?

  Yeah.

• 1:37:09Lester Nare?

  In an order or orders of magnitude from what you would otherwise be doing with the current conventional options.

• 1:37:16Krishna Choudhary?

  Exactly. Yeah. I mean, I think it's an incredibly exciting time for electronics at the cutting edge.

• 1:37:23Lester Nare?

  Yeah.

• 1:37:23Krishna Choudhary?

  Right? Because all we're starting to see that things like GPUs and things that are capable of doing matrix multiplication and things like that are going to become increasingly important. Perhaps even more important than traditional von Neumann architectures. We've still got a long way to go, so I do want to temper the brakes here and not dream too much. Because memory alone does not make a complete computer. You need high temperature logic circuits that also need to be developed and integrated alongside whatever chip that you're trying to put in. And current devices are built by hand, sub micron scale in the lab. The this is from their paper in the supplement. That length bar there says five micrometers. Okay?

• 1:38:08Krishna Choudhary?

  So that's, that's like a thousand times bigger than the chips that we have, like the transistors that we have in our, in our chips, in my computer, for example. So we got to make this thing smaller while still retaining the memorister characteristics, the graphene. That's going to be a problem, right? Scale up is going to take time. On the manufacturing side, two of the three devices, two of the three materials in this device, namely the tungsten and the hafnium oxide. Those are already standard.

• 1:38:39Lester Nare?

  Right.

• 1:38:40Krishna Choudhary?

  In semiconductor manufacturing, right? Making the graphene smaller, that's going to be kind of tough, right? It's newer to the industry. But actually, TSMC and Samsung both have that in their development roadmaps. If you go look, you know, they have like the shareholder like pitch decks or like, we're still innovating, guys. You know, so they have graphene. In their roadmap and it's already grown at wafer scale in research settings. We need to make it industrial if we want to have this thing grow. I mean, the startup that these USC scientists Tetra Mem, co-founded by Joshua Yang and Xia. I mean, it's already like doing things.

• 1:39:20Krishna Choudhary?

  So we're, we're, we're heading for a new era in computation in a era where computation is becoming the bread and butter for our society more than ever, more so than ever. I mean, we used to think, right? Ever since the advent of the nineties and the advent of the personal computer, the computation would be big. Now it's like cloud computing and these large scale computing.

• 1:39:44Lester Nare?

  Yes.

• 1:39:44Krishna Choudhary?

  Large scale computing is now taking precedence over personal, small scale computing.

• 1:39:49Lester Nare?

  Yeah.

• 1:39:49Krishna Choudhary?

  Right? So we're, we're entering into a new era of computation. We've lived through one in the nineties and now this is a new one.

• 1:39:58Lester Nare?

  As if, as it relates to TSMC, it's interesting that both TSMC and Samsung are already working on, you know, you know, integrating graphene into their industrial process. As if we needed another reason for Taiwan to be a geopolitical.

• 1:40:11Krishna Choudhary?

  Ah, yikes.

• 1:40:12Lester Nare?

  Yeah. Matchbox.

• 1:40:13Krishna Choudhary?

  Yeah.

• 1:40:14Lester Nare?

  Particularly given the stakes of the perceived and real benefits of the race as it relates to AI writ large.

• 1:40:26Krishna Choudhary?

  Yeah.

• 1:40:26Lester Nare?

  Um, it, this is going to be, and again, you know, we talk about breaking science. Research papers on this story, there is a delta between or a distance between it working in a lab and it being in your phone at home or in a data center in space. But it is a, we're trying to continue to build this roadmap for people to understand where we're going as a society and what some of the best and brightest among us are trying to bring to us. And again, we talked about this in the context of data centers in space, but there are other things that you've mentioned, you know, that would be used, this will be useful for an extreme computing.

• 1:41:09Krishna Choudhary?

  That's right.

• 1:41:10Lester Nare?

  Exploration and other things. So.

• 1:41:11Krishna Choudhary?

  Space exploration, I'd like to get better photos of Venus.

• 1:41:15Lester Nare?

  Yeah, yeah.

• 1:41:16Krishna Choudhary?

  That'd be really nice.

• 1:41:17Lester Nare?

  That'd be great.

• 1:41:17Krishna Choudhary?

  Um, I'd like to have a rover on Venus that's like running around and stuff. That would be cool.

• 1:41:21Lester Nare?

  Yeah.

• 1:41:22Krishna Choudhary?

  Heavy energy like geothermal.

• 1:41:25Lester Nare?

  Right.

• 1:41:25Krishna Choudhary?

  Nuclear monitoring.

• 1:41:26Lester Nare?

  Right, right.

• 1:41:26Krishna Choudhary?

  I'd like to have safer nuclear.

• 1:41:29Lester Nare?

  Yep.

• 1:41:30Krishna Choudhary?

  Um, power.

• 1:41:31Lester Nare?

  If you're a green or clean energy person, I mean, this can have real, real impacts in that space because it can help us better both understand and also execute in terms of production, maintenance, operational aspects.

• 1:41:46Krishna Choudhary?

  Yeah, really anything that requires high temperature computing, right? I mean, with the advent of fusion, right? If we're trying to make fusion a thing, stuff is hot.

• 1:41:55Lester Nare?

  Yep.

• 1:41:55Krishna Choudhary?

  And so if we want real time monitoring and decision making using some AI algorithm about how to confine the plasma, I'm just thinking out loud, right? Like that's something.

• 1:42:04Lester Nare?

  That this would be used for.

• 1:42:06Krishna Choudhary?

  I don't need like to cool it down to room temp. I can just cool it down to 700 degrees.

• 1:42:10Lester Nare?

  Who needs a room temperature semiconductor?

• 1:42:13Krishna Choudhary?

  Yeah.

• 1:42:14Lester Nare?

  Well, we still want that.

• 1:42:14Krishna Choudhary?

  We still want that, yeah.

• 1:42:15Lester Nare?

  We still want that. This was a really great electronics that can survive lava. Again, this was a recent science paper, March 2026, a collaboration led by researchers here in California, forever goodbye at USC alongside the Air Force Research Lab in Dayton, Ohio and the Kumamoto University in Japan with funding from the National Science Foundation, the Army Research Office and the Air Force Research Lab. Can't wait to see a, a high temperature murmurs in a hypersonic vehicle near you.

• 1:42:58Lester Nare?

  Because certainly they're going to be using it for command and control systems integrated with, you know, next generation military stuff. So before they do that, we would like to have it be used for the good of mankind. Do you have any last notes before we wrap up today?

• 1:43:15Krishna Choudhary?

  No, um, if you want to leave a comment, think of a really funny application for high temperature computing. Where would you want to put a chip? Run wild.

• 1:43:26Lester Nare?

  Keep it PG, everybody. This is a family friendly show. As always, my name is Lester Nare, joined by my co-host, our resident data centers in space, our possible PhD Krishna Choudhary. We are approaching our one year anniversary. So be sure to be tuned in for our anniversary episode. For our long time listeners, we are extremely grateful. If you just happen to be listening to us for the first time, catalog is a bunch of episodes that are just like this, 50 of some of the best science entertainment on the planet. We will see you all next week.