Ambient scanning tunnelling spectroscopy of sulphur passivated InP(100) surfaces

The results of scanning tunnelling spectroscopy (STS) studies of wet chemical sulphur passivated InP(100) surfaces are presented. The aim of the study was to attempt to establish a more quantitative measure of the surface passivation using the STM. Current voltage (I-V) spectroscopic plots for sulphur passivated and native oxide surfaces displayed distinct differences previously reported for GaAs(100) surfaces. Current distance (I-S) spectroscopic results for both passivated and unpassivated InP surfaces and the accompanying apparent barrier height (φA) measurements are presented along with a justification of the results. For reference purposes, φA measurements of the Au(111) surface were made to establish the validity of the (I-S) spectroscopic technique in air. The chemical composition of the InP(100) surface before and after sulphur passivation is determined by X-ray photoelectron spectroscopy (XPS) measurements.