HOT-ELECTRON SCATTERING EFFECTS IN METAL-SEMICONDUCTOR STRUCTURES ANDTHEIR ROLE IN INTERFACE TRANSPORT

The spectroscopy mode of ballistic electron emission microscopy was us ed to study the thickness dependence of the collector current I(c) for 8-90 angstrom thick Pd films deposited on Si(111) and Si(100) substra tes. The observation of similar spectral intensities for the thinnest films on both orientations is attributed to disorder induced scatterin g at the Pd-Si interface, which is conventionally equivalent to a brea kdown of transverse momentum conservation. Fits to a model based on th is interpretation give unprecedented agreement over a wide energy rang e. The attenuation of I(c) with film thickness exhibits strong nonexpo nential behavior for all tip biases studied (less-than-or-equal-to 6 V ), which is due to a changing dominance among scattering mechanisms as the film thickness varies. A simple analytical expression, based on a random-walk approach, is derived that allows a unique determination o f the energy dependent elastic and inelastic mean free paths of hot el ectrons in the Pd films.