Atomic Resolution Imaging and Measurement of the Local Density of States of Graphite, Gold and Silicon using Scanning Tunnelling Microscopy

TL;DR

This paper demonstrates atomic resolution imaging and local density of states measurements of graphite, gold, and silicon using scanning tunneling microscopy, providing experimental lattice constants, work functions, and LDOS variations.

Contribution

The study applies STM and STS techniques to measure atomic-scale properties and LDOS of materials, with experimental validation and comparison to literature values.

Findings

Lattice constant of HOPG measured at 0.27 nm

Work functions for gold and graphite determined as 0.7 eV and 0.5 eV

LDOS hierarchy: gold > graphite > silicon

Abstract

A series of experiments were conducted using the STM instrument, which involves a conducting tip probe to analyse sample surfaces by measurements of a tunnelling current. In this experiment, STM was used to (1) determine the lattice constant of Highly Oriented Pyrolytic Graphite (HOPG) by acquiring atomic resolution images of its surface, (2) measure the work functions of gold (Au) and HOPG samples using the STS mode and, (3) compare the variation of the Local Density of States (LDOS) of gold, graphite and Silicon (Si) samples with respect to bias voltage V. Experimental values of the lattice constant of HOPG and work functions for gold and graphite were determined as 0.27 +/- 0.2 nm, 0.7 +/- 0.1 eV and 0.5 +/- 0.1 eV respectively. The lattice constant deviated slightly from the literature value of 0.246 nm, whereas the work functions deviated significantly from the literature values of 5.40 eV for gold and 4.62 eV for graphite. The LDOS for gold was found to be the highest, followed by graphite, then silicon. These findings will be discussed.