Quantum-mechanical analysis of the elastic propagation of electrons in the Au/Si system: Application to ballistic-electron-emission microscopy

We present a Green's-function approach based on a linear combination of atomic orbitals scheme to compute the elastic propagation of electrons injected from a scanning tunneling microscope tip into a metallic film. The obtained two-dimensional current distributions in real and reciprocal space furnish a good representation of the elastic component of ballistic electron emission microscopy (BEEM) currents. Since this component accurately approximates the total current in the near-threshold region, this procedure allows-in contrast to prior analyses-to take into account effects of the metal band structure in the modeling of these experiments. The Au band structure, and in particular its gaps appearing in the [111] and [100] directions, provides a good explanation for the previously irreconcilable results of nanometric resolution and similarity of BEEM spectra on both Au/Si(lll) and Au/Si(100). [S0163-1829(98)01243-0].