What did we do?

First, we went to the STM, to see the effects of the bakeout. The different parts of the microscope were becoming warm, in order to get rid of water and other molecules.



Then, we visited another STM lab, which studies electronic properties: the effects of the thickness of the sample on superconductivity are analyzed. There are only a few monolayers of atoms (10-15) and the studied system doesn't behave like a volume. For example, the critical temperature decreases.

The tunneling spectroscopy enables us to know if the material is locally nonconductor. A magnetic field is applied to the system, to create vortexes, which are analyzed in order to know the superconductivity properties of the sample.

The microscope mustn't touch the walls of the vacuum chamber, because it has to be mechanically isolated.


Later, we talked with the researcher who uses the atomic force microscope. A diapason is approaches to the surface. The diapason has a natural frequency of vibration. When it is near the surface, there are interaction between the surface and the tip, so the frequency and the amplitude change. The tip mustn't touch the surface.

The materials studied are monocrystals. The lattice is cleaved in order to have a planned surface. If bumps. are detected, they are structural defects. These defects play a role in the electronic state of the material.