Nanocar Race Part 4: The Track – Preparation of the sample
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.
Nanocar Race 2017
The NanoCar Race is an event in which molecular machines compete on a nano-sized racetrack. These “NanoCars” or molecule-cars can have real wheels, an actual chassis…and are propelled by the energy of electric pulses! Nothing is visible to the naked eye, however a unique microscope located in Toulouse will make it possible to follow the race. A genuine scientific prowess and international human adventure, the race is a one-off event, and will be broadcast live on the web, as well as at the Quai des Savoirs, science center in Toulouse.
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