Electrostatic effects of nanoscale dielectric patches in the modification of Schottky contacts

Abstract

We study the electrostatic effects of thin organic films in modifying the interface physics of metal/semiconductor Schottky contacts. We work out analytically the electrostatic parameter space pointing out where interface state effects exceed space-charge effects and vice versa. This is done by introducing another treatment of the electrostatic problem. We also find that the image force effect on the barrier height due to the insertion of a material with lower dielectric constant than the semiconductor in between the Schottky contact is small but positive. This is in contrast to what might be expected from effective-medium theory. We conclude with an examination of ballistic electron emission microscopy results of pentacene modified $\text{Au}/n\text{-Si}(111)$ Schottky diodes as a case study. Using the tools fore mentioned, we infer the local charge neutrality level and density of interface gap states (to an area of $500\ifmmode\times\else\texttimes\fi{}500\text{ }{\text{nm}}^{2}$) from barrier height statistics and pentacene monolayer heights.