Momentum conservation for hot electrons at the Au/Si(111) interface observed by ballistic-electron-emission microscopy

Ballistic-electron-emission microscopy (BEEM) spectroscopy was performed at room temperature and at 77 K on Au/Si(111) structures. Au thickness was varied in the range 75–300 Å. At 77 K a direct signature of parallel momentum conservation is observed in the BEEM spectra of samples with thick Au layers. The change in spectral shape which was observed as a function of both Au thickness and temperature places restrictions on allowable values of inelastic and elastic mean-free paths. The observations also suggest the presence of multiple reflections of the injected electrons within the Au layer. An independent indication of these multiple reflections is observed in the dependence of BEEM current on Au thickness in Au/Si(100) structures. Calculations provide good agreement with observed BEEM spectra and attenuation length data.