Atomic theory of the scanning tunneling microscope

The Scanning Tunneling Microscope is proven to be one of the most powerful tools for surface structure determination. Present theories are able to explain the operation of the microscope when the tip is far from the surface. For the small tip height case the atomic-scale interaction of the tip and the surface has to be included in the theory. The electronic structure of the combined system of the tip and the surface is calculated with an Empirical Tight Binding approach for graphite. It is found that in the vicinity of the tip some Tip Induced Localized States are formed. These states play an important role in the tunneling phenomenon. The contribution of these states to the tunneling current is calculated.