CHEMICAL-REACTIONS INDUCED BY THE ROOM-TEMPERATURE INTERACTION OF HYPERTHERMAL ATOMIC-HYDROGEN WITH THE NATIVE-OXIDE LAYER ON GAAS(001) SURFACES STUDIED BY ION-SCATTERING SPECTROSCOPY AND X-RAY PHOTOELECTRON-SPECTROSCOPY

A surface characterization study using x-ray photoelectron spectroscop y (XPS) and ion scattering spectroscopy has been performed on solvent- cleaned, n-type GaAs(001) substrates before and after room temperature exposure to the Aux produced by a novel atomic hydrogen source based on electron-stimulated desorption of hyperthermal (similar to 1 eV) hy drogen atoms. The native oxide layer on the solvent-cleaned GaAs(001) substrate contains C, As2O5, As2O3, and Ga2O3 according to the XPS dat a with Ga2O3 being the predominant species. Before H atom exposure, th e C is present as hydrocarbons, carbonates, alcohols, and carbides wit h hydrocarbons as the predominant chemical stale. Upon room temperatur e exposure to a 1 eV hyperthermal H atom flux, the O in As and Ga oxid es is removed, and the amount of C present is reduced through methane formation and desorption. In this process hydrocarbons are not convert ed to carbides, which are difficult to remove, as in the case of ion s puttering. After reduction the predominant form of O is a subsurface, dissolved O, and the outermost atomic layer is enriched in O by a chem ical-induced driving force. (C) 1997 American Vacuum Society.