Method to determine defect positions below a metal surface by STM

TL;DR

This paper presents a theoretical method using conductance oscillations in STM to locate defects beneath a metal surface by analyzing quantum interference effects in tunneling and ballistic contacts.

Contribution

It introduces a novel theoretical approach to determine defect positions below metal surfaces through conductance oscillation analysis in STM.

Findings

Conductance oscillations depend on defect position.

Quantum interference causes measurable conductance oscillations.

Method applicable to tunnel junctions and ballistic contacts.

Abstract

The oscillatory voltage dependence of the conductance of a quantum point contact in the presence of a single point-like defect has been analyzed theoretically. Such signals are detectable and may be exploited to obtain information on defect positions below a metal surface. Both tunnel junctions and ballistic contacts of adiabatic shape have been considered. The effect of quantum interference has been taking into account between the principal wave that is directly transmitted through the contact and the partial wave that is scattered by the contact and the defect. This effect leads to oscillations of the conductance as a function of applied voltage. We obtain the dependence of the period and amplitude of the conductance oscillations on the position of the defect inside the metal.