Experiment nr. 21

Study of Solid State Surfaces using a Scanning Tunnelling Microscope

Supervisor: Dr. habil. Michael Lorenz, Wolfram Fritzsche

In the experiment Scanning Tunneling Microscopy STM the lateral electron density distribution of  solid state surfaces will be depicted. This allows under optimised conditions to visualize single atomic positions. Beside it, more extended objects as quantum dots and monolayer terraces with dimensions in the nm-range will be represented.

The scanning tunneling microscope is based on the quantum mechanical tunnel effect. In addition to the imaging of the surfaces, current-voltage curves in dependence on the distance from tip to surface and current-distance curves are recorded. By fitting appropriate model equations the barrier height of the particular tip-sample combination can be determined.
Methodical aspects cover the different scan modes of a STM and the piezoelectric materials which enable the STM experiments by controlling the tip position with sub-nm accuracy. The experiment gives direct practical experience by application of this modern method of surface physics.