Surface and bulk band-structure effects onCoSi2/Si(111)ballistic-electron emission experiments

Abstract

A theoretical model of ballistic-electron-emission microscopy (BEEM) based on linear combination of atomic orbitals Hamiltonians and Keldysh Green's functions is applied to analyze experimental data obtained for ${\mathrm{CoSi}}_{2}/\mathrm{Si}(111)$ contacts. Hot electrons injected from a scanning tunneling microscope tip into the silicide film form a highly focused beam, which even after propagation through films of moderate thickness is narrow enough to allow the observed atomic resolution of interfacial point defects. On $(2\ifmmode\times\else\texttimes\fi{}1)$ reconstructed domains a certain fraction of the initial current is injected into localized surface states, leading to the reported contrast in BEEM images, reflecting the topography at the surface. These results confirm that band-structure effects, both in the bulk and at the surface of the metallic overlayer, intricately influence the interface-related information contained in BEEM data. It is found that for a careful analysis of experimental results, a theoretical model going beyond the ballistic hypotesis is required.