Why conventional memristors fail when hot

41:02Why tungsten? Well, tungsten is has a very high affinity for oxygen. So, that's good. It's 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? 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 memor is the following. We've got a top electrode. We've got a bottom electrode, tungsten, halfneeium oxide, something else. >> Mhm. >> And we use the oxygen vacancies in the half oxide to

41:45transport electrons and turn that highway on or off. >> Okay, >> that's effectively the idea. 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. >> 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 hnneium 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

42:26metal. 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 veilance charge mechanism takes over, right? The problem is when you pump up the temperature at high temperature, the tungsten starts diffusing, >> right? If you get into a high enough temperature, the tungsten now starts jiggling around and the tungsten starts exploring the forest. >> Okay? >> And we don't want that. We don't want that. We just want oxygen. >> We we want only the oxygen to move around, create these vacancies, and then

43:06there'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. >> Mhm. >> Now, there's no way to I mean, even if you cut down all the trees, you've just paved a highway >> for that. Yeah. Yeah. Yeah. And there's no it can no longer cycle. >> Yeah. Yeah. Why would anyone take the trees? You just go through the highway. Right. >> Right. You go through the tungsten and the platinum filaments. And that's been the big problem, right? They mix in ways that destroy this precise nanocale structure. Platinum and tungsten is not the way. Okay? You're going to effectively short circuit at high

43:46temperatures. At low temperatures, this thing is working >> great. Right? But you you start pumping this thing up to 500, 600, 700° C. All of a sudden, the the metal atoms in the two electrodes, they start getting agitated. This this is giving me uh a feeling similar to the hypersonics episodes we talked about where Navier Stokes gets weird >> at higher temperatures. And so there's different regimes depending on the temperature band you're working in and I'm I'm just making making the connection between the two things. >> Yeah. Different physics starts mattering. Right. Right. It's like it's like the the the titanium to titanium bond

44:27>> is now smaller than the thermal noise. Yeah. >> And so the titanium's like, "All right, I'm going to dip out. Let's start exploring. I don't know. I'm going to go this way." [laughter] And the platinum's like "Hey hey >> 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 memeister, 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. >> But then as we got to higher temperatures, physics gets different. And it does our the current regime of tungsten and platinum >> doesn't work. >> Doesn't work. >> Yes. Exactly. And now we get to the

45:08paper. Okay. This was out in science. Um shout out. >> Um high temperature meristers enabled by