Tip apex charging effects in tunneling spectroscopy

TL;DR

This paper investigates how the charge accumulated at the tip apex of an STM affects electron transport through surface quantum states, combining theoretical models with experimental validation.

Contribution

It introduces a combined theoretical and experimental analysis of tip apex charging effects on tunneling spectroscopy, highlighting the impact of tip sharpness on conductance symmetry.

Findings

Sharp tips become extra charged, breaking conductance symmetry.

Experimental results on Ag islands confirm theoretical predictions.

Tip shape influences electron transport properties.

Abstract

The influence of charged STM tip on the electron transport through quantum states on a surface is studied both theoretically and experimentally. The current and the differential conductance calculations are carried out by means of the Green's function technique and a tight-binding Hamiltonian. It is shown that sharp STM tip is extra occupied and this additional charge breaks the conductance symmetry for positive and negative STM voltages. The experiment on Ag islands with two STM tips (blunt and sharp) confirms our theoretical calculations.