Theory of tunneling spectroscopy for semiconductors

Abstract

It is generally accepted that scanning tunneling microscopy and scanning tunneling spectroscopy (STS) get their information from the sample local density of states. At present, however, there is little theoretical ground on which to explore this assumption. We contribute here with a theory of STS for semiconductors, treated within the tight-binding approach. In the context of this theory, we demonstrate that the current-voltage (I-V), and the conductance-voltage (\ensuremath{\sigma}-V) curves are related to the density of states. In particular, the current is a sum over tip states of semiconductor local density of states modulated by tip-dependent coefficients. This result is consistent with those found in previous works. The \ensuremath{\sigma}-V curve has nondifferentiable points which are a direct manifestation of the Van Hove singularities in the global density of states of the semiconductor.