Investigation of local tunneling barrier heights

In one of the first publications on STM, Binnig and Rohrer discussed the possibility of recording the local tunneling barrier height F by a modulation experiment [9]. Then-result can be summarized with the following equation:

where A » 1.0251 eV"1. Â"1, Iq represents the initial current and s the tip-sample distance.

By modulating the distances between tip and sample surface and recording the varying tunneling current 7t it is possible to deduce the local barrier height by Eq. (1). Changing the chemical composition of either the substrate or the tip leads to different local barrier heights. Differences in the chemical composition of the substrate therefore result in various barrier potentials.

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