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  • Christmas winter is usually pretty cold in here.

  • It's absolutely roasting.

  • I'm sweat and Brady stripped down to his own pants.

  • Not quite.

  • It's really, really hard on.

  • The reason it's hard in here is, though.

  • Inside here we are baking one of our ultrahigh vacuum systems.

  • We heat it up 250 degrees, and you'll see if you look at this other system, which isn't being big, you'll see this tin foil everywhere.

  • The reason for the tin foil is is to keep everything nice and toasty, and the reason we bake it is because we want to drive off all the water that's on the surfaces, and then when we cool it down, it reaches a really, really fantastic pressure.

  • But enough about what we're actually here to do is to try on Mick the world's smallest Christmas tree.

  • So over here, what's the system?

  • Because actually, what's happening is that this is the system in which everything is happening.

  • Morton, who is the student who's been doing most of this work alongside all of his colleagues, has put a very touching Christmas message torch and you will be killed on the system.

  • That's because this experiment is quite tricky.

  • What's happening, what you're seeing on the screen now the Simmons that's building up.

  • It's happening right in here, which means we don't touch that machine.

  • We don't walk into what we don't bounce into it.

  • Now our surface is not great or surfaces, as you can see all these little specks, what first of all this is 20 nanometers.

  • So these little specks are actually individual molecules, individual atoms.

  • But there are individual atoms that have come out of the vacuum.

  • The residual gases in the vacuum under corrupting our samples are samples been in there a long time, so the underlying surfaces silicon.

  • But it's a special type of silicon service.

  • It's a silicon surface where we've taken all the bonds of the surface that stick out of the vacuum and covered them with hydrogen.

  • So what the surface?

  • What happens is that the silicon atoms pair up each one of these grey.

  • Think of each one of these great things is a silicon atom on that silicon atom is bonded to three others.

  • So one two can you see the pretty three.

  • Maybe if I tilted like they responded to three others responded to this one.

  • It's bonded to that one.

  • Responded it out, one which leaves this one sticking up, out into the vacuum on that we call a dangling bond.

  • And normally that incredibly reactive.

  • So what we do is we expose the surface, toe, hydrogen.

  • This is one of our hydrogen on.

  • We come along and we cap those silicon bonds.

  • So this is incredibly on reactive.

  • It's a very inert, very passive surface.

  • Each of those silicon atoms that are exposed to the surface of basically wearing a hat.

  • Exactly.

  • That's exactly it.

  • Yes, we put a little half and we put it in a hydrogen hat on each one of the dining bones on.

  • So here, we've got a bear silicon on here.

  • We've got the hydrogen counseling, and now we love when we do the hydrogen exposure.

  • We'd love if it was his natives.

  • This that every single silicon bongo title.

  • But we don't.

  • We have some natural bonds that are left over.

  • But the great thing on what we're gonna talk about this this video is that you can actually take one of these.

  • Hydrogen is off.

  • We have a sharp tip.

  • We bring it in close to the surface.

  • I want to stay close.

  • I mean, within a couple of atomic diameters on we move it back and forth across the surface.

  • What we're doing all the time, Mrs Quantum mechanics in action, is we're measuring a tiny, tiny current of electricity.

  • Tiny flow of electrons between the tip on the sample.

  • Even though they're not in contact, we still have electrons form.

  • That's an effect called quantum mechanical tunneling.

  • Using is a measure desperate can also use it as a manipulation device as well.

  • You can do one.

  • You're up here, you can measure that current, and you don't really disturb the surface too much.

  • But what you can do is you can do a number of things.

  • You can increase the voltage on, shoot in a pulse of electrons, which shakes up this autumn and causes it to come off.

  • And you could do with that precisely.

  • Or indeed, you can come on in very much closer and actually bond to it and take it off that way.

  • But what we're gonna do is we're gonna hold the tip above it, inject the flow of electrons, increase the flow of electrons, and it heated up, heated up locally, and that's exactly what we're doing.

  • We're causing it to vibrate and to come off.

  • That's the idea.

  • Anyway, I need to point out, of course, that we didn't pioneer this.

  • The person who developed this on the group that developed this was a university Illinois, back, actually, In the mid 90 somebody called Joe lighting fantastic work.

  • They introduced this on then from your home country, bready.

  • Somebody who's really taking this or no one with that is Michelle Symonds Group in University.

  • New site wears They've pushed this all the way down to making single atom transistors.

  • So what I wanna do is I'll try and show you one removed we've done over the past few weeks.

  • A couple students been working really, really hard on this technique on.

  • They really pushed it too well, certainly for us to get in very high levels of precision.

  • They've done a really, really nice Christmas tree, so we will show you that later on.

  • But for now, let's just look at the process in action for a single bond.

  • So what we see here is a fairly cruddy silicon.

  • Hydrogen postulated silicon surfaces a lot off because we've had this in the system for a long, long time.

  • There's a lot of stuff has ended up landing on the surface and sticking their terms.

  • But I'd love to be able to tell you one of the disadvantages of scanning tunneling.

  • My cross gives you see blobs.

  • You know, the stuff there trying to work out.

  • The chemical nature of that is very, very tricky In the system, we've got water, residual water, even though we bake it.

  • It's really hot in here.

  • Even though we bake the system, we still got some residual water.

  • The seal, the seal to those are the key contaminant in the system.

  • What we're gonna do, we're gonna let it build up an image on what it's basically doing.

  • As you can see the green lang going back and forth, it's moving the tip back and forth across the surface on measuring that current and from that current generating an image of the atoms.

  • And now what we're going to do once it's acquired this image, we're gonna hold the tip at above a certain point in Jack's, um, electrons and hopefully dissolve hydrogen.

  • You might expect when you dissolve the hydrogen.

  • The image might look darker because there's no longer a bump there.

  • But the important thing is by dissolving the hydrogen, you change the ability for electrons to flow through this bond on.

  • In fact, the electrons find it easier to flow through this exposed bond.

  • So you get a big, bright patch in the image.

  • I'm gonna try and end this curse there is.

  • That's right.

  • Let's try here.

  • Yeah, and it worked.

  • So that little block that little white spla JJ brilliant.

  • I didn't think it worked.

  • First time that little bit brights lodge is where we dissolved a hydrogen atom on it.

  • What's that?

  • Yeah, exactly.

  • On that we can do a few more.

  • Let's get that hold scan.

  • This is where it gets boring bread because we gotta wait for to come down and go back up against we get the full scan.

  • Absolutely.

  • Absolutely.

  • No, it's It's fantastic.

  • And the problem is, it can become a damn.

  • You sit in a lab really hard.

  • You're sweltering.

  • Andi can come for a little mundane, but you've got to stand back every now and again and go.

  • Yes, Why actually dissolved an atom?

  • We move atoms around.

  • We see Bonds, it's it's just staggering, absolutely staggering, and that this is possible.

  • Exactly exactly.

  • You just click a point and click on offered Combs.

  • It's most of the time, not all that lets in True Blue Peter Fashion show you one that we did earlier.

  • So this is the work of Morton, whose PhD student here unfortunately had to catch a flight back to Sweden yesterday.

  • But he did a Christmas tree on DDE.

  • I don't think it's about Christmas tree.

  • Each one of these is where the hydrogen atom has been dissolved.

  • Its blob is where we've stripped off one of the hydrogen atoms.

  • So it's like that is like a crowd of people at a football game, and we can see all the people who took their hats off.

  • Yeah, that's exactly what it's like.

  • Yes, it's basically a Ziff.

  • You're looking top down, and people have taken the hearts off.

  • Each one is where we've removed the hydrogen.

  • How many hydrogen atoms he removed to make that business trip?

  • Uh, this is good.

  • 42.

  • Well, certainly let's put it this way.

  • The algorithm that we counted up the algorithm that uses the X Y coordinates.

  • There were 42 different sets of ex wife Warden.

  • I don't know if he's a Douglas Adams found or not, but I find that a nice coincidence.

  • The next Christmas present for me, Saturn and Jupiter very close to each other in the sky.

  • On this is something that that astrologist kind of get very hung up about.

  • They think that it actually means something of great significance when you have one of these conjunctions, especially between the major planets.

Christmas winter is usually pretty cold in here.

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世界最小のクリスマスツリー(42個の原子から作られています (World's Smallest Christmas Tree (made from 42 atoms))

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    林宜悉 に公開 2021 年 01 月 14 日
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