HIGH-RESOLUTION PHOTOEMISSION-STUDY OF THE INTERACTION OF HYDROGEN WITH GAAS(110) SURFACES

We present a synchrotron-radiation photoemission investigation of hydrogen chemisorption on GaAs(110) surfaces cleaved in situ. Analysis of the valence-band emission and high-resolution core photoemission studies as a function of hydrogen coverage and photoelectron escape depth show that at least in the high-coverage regime hydrogen chemisorption occurs via the formation of surface bonds between atomic hydrogen and both As and Ga atoms. Decomposition of the As 3d and Ga 3d core lines in terms of bulk and surface components demonstrates that hydrogen adsorption is accompanied by preferential etching of As, roughening of the surface, and a consequent relatively large variation of surface stoichiometry toward a Ga-rich composition.