Variable-height scanning tunneling spectroscopy for local density of states recovery based on the 1D-WKB approximation

Abstract

We introduce a variable-height scanning tunneling spectroscopy (VH-STS) method that provides a good level of recovery of the combined surface and tip density of states (DOS) in any bias range without the complexity of previous methods. The combined local electron DOS (LDOS) recovery was performed using a simplified algorithm based on the one-dimensional Wentzel-Kramers-Brillouin approximation already known in the literature. On the basis of this VH-STS approach we derive three separate methods for the determination of tunnel barrier height and absolute tip-surface separation, and which are critical to enabling LDOS recovery. We report experimental results on polycrystalline-Pt and Si(100) surfaces using this scheme. Experimental and simulated spectra are compared to investigate the limits of the various methods and to demonstrate that this approach can be applied successfully to all kind of probes and surfaces.