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(111) and Au/Si(100).

• Received 1 May 1998

DOI:https://doi.org/10.1103/PhysRevB.58.14036