Gold–silicon interface modification studies

We have performed ballistic electron emission microscopy measurements on the Au–Si system with and without controlled monolayer impurities at the interface. At moderate sample to scanning tunneling microscopy tip biases (<2.5 V) we have observed, and at high biases (>3 V) modified the local ballistic transmittance (BT), i.e. the scaling factor of the collector current versus voltage spectra, of the interface. Spatially, the modification typically consists of a region of decreased BT a few hundred Å in diameter surrounded by a ring of increased BT. No change in Schottky barrier height is found. A model is presented which describes the decrease in terms of Au–Si interdiffusion, and the enhancement in terms of a thinning of an impurity layer between the Au and Si; connections are made to observations of the unstressed system.