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Nanocar Race 2017: 5. The Track – Preparation of the sample

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Nanocar Race 2017: 5. The Track – Preparation of the sample
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5
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163
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CC Attribution - NoDerivatives 4.0 International:
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Abstract
We use a gold sample consisting of a perfect single crystal. It is pure gold and the atoms are perfectly arranged to a crystal. On the 111 surface of the gold crystal a reconstruction of the surface atoms takes place. The atoms arrange like a herringbone. That’s why it is called herringbone reconstruction. The race track of the Nanocar Race is along such a herringbone reconstruction. The reconstruction is the side rail of the track that we are not allowed to cross. Each team has to do three straight lines and two turns. In total this is a distance of approximately 100 nm. It is not possible that we all start at exactly the same position and take the same race track because we cannot bring 4 STM tips so close together. But the reconstruction is the same all over the sample surface. So each team has one quarter of the sample and chooses one molecule which sets the race track. First, we have to clean the race track to be sure that there are only the nanocars and no other molecules from previous measurements. In order to clean the sample we have to move the sample from the microscope to the preparation chamber. Afterwards we do sputtering and annealing cycles. . For sputtering you bombard the sample surface with ions to get rid of all contaminations. Annealing means that we heat up the sample so that the atoms rearrange after the sputtering and form flat and large terraces. If the surface is cleaned, we start with the second process. To put the nanocars on the surface we heat up the crucible where the powder of the molecules is inside. If a certain temperature is reached, the molecules are evaporated and fly towards the sample surface where they are deposited. Finally we have to transfer the sample back to the microscope.
Keywords
Tidal raceMoleculeTidal racePotenz <Homöopathie>Computer animationMeeting/Interview
QuartzGoldTidal raceMeeting/Interview
Surface scienceAtomic numberMatchWalkingChemical experiment
Atomic numberWalkingMeeting/Interview
Computer animation
Terrasse <Geologie>Atomic numberWalkingTidal raceMeeting/Interview
Computer animation
Surface scienceComputer animation
Tidal raceMeeting/Interview
Computer animation
Sample (material)Cell (biology)Meeting/Interview
Ice frontSample (material)Combustion chamberWursthülleBacon
Surface scienceSample (material)Powdered milkRadiation damageScrubberPotenz <Homöopathie>StuffingIsland
MoleculeSurface scienceHuman body temperatureChemical experiment
Chemical experiment
Surface scienceMoleculeChemical experiment
Meeting/Interview
Sample (material)GesundheitsstörungMoleculeCombustion chamberCuring (food preservation)OperonChemical experiment
GesundheitsstörungMeeting/Interview
Transcript: English(auto-generated)
In the nanocar race, just like in any other car race, you will be racing on a specific racing circuit, right? We already talked about that a little bit in the last video when we learned about how to control a single molecule just like a car. Can you tell me more about the racing track? Yeah, for the racing track we use a single gold crystal that you can see here.
And it's a very clean and flat surface. But is it flat all the way? No, it's not flat all the way. So look at the STM image. And there you see some steps. And these steps are coming from layers of atoms. So if there's one layer of atoms more, you get a step. So that's kind of an edge you should try to avoid, right?
Because otherwise your car will fall down and crash. Exactly, we should avoid these step edges. That's why we choose for the racing track a flat and large terrace here. So I zoom in to show you what we use. So here you see again the rails of the racing track. But on this image I can also see some dark spots. What's that?
The dark spots are exobates that come on the surface and we try to avoid them because we cannot pass. So we choose the racing track here in the middle. And we do one straight line, a turn, again a straight line, a second turn and then we go straight again. So in total 100 nanometers. Okay, and will all teams be racing on exactly the same circuit?
That's not possible. We will use the same sample but we cannot use exactly the same circuit. And that's why we go to Toulouse. They have a special microscope, they have four tips. So four teams can compete at the same time. And how do you get all those cars down on this little sample?
This I show you in our preparation chamber. Let's go there and see. We are back in front of the microscope. To prepare the sample we have to bring it to the preparation chamber. But you can't see anything in here, right? No, you cannot see anything there. So first we have to clean up the surface. And how do you do that? Do you scrub it with a rag or something?
That's not clean enough for us. So what we do is we use a sputter gun and we bombard the surface with ions. Okay, bombardment sounds like a lot of forest. Does it leave any damage on the surface? Exactly, the surface is completely damaged. So that's why we have to anneal the surface. So we heat up the sample to get a flat surface again.
Okay, now that your surface is flat and clean again, how do you get the cars onto that? What we do is that we heat up the powder that you see here. And if a certain temperature is reached and the molecules are evaporated and they fly around and some of them go to the surface and stay on the surface. But it's not just your team. I mean there are four teams. Do all teams evaporate the molecules at the same time?
That's not possible. That's a technical challenge for us. So every team has special conditions for the preparation of the sample and all molecules have to come on the same sample. So that's really a technical challenge. Okay, and then now that your sample is prepared, what happens next?
Then we have to bring it back to the microscope. So we have to transfer it from the preparation chamber to the analysis chamber. And there are special conditions in the analysis chamber. And we'll talk about these special conditions in another video that you will as always find, linked below. I hope I'll see you again there and have a good time. Bye bye.