Interaction of oxygen with a potassium-covered GaSb(110) surface at 500 K

The interaction of oxygen with a GaSb(110) surface precovered with 0.9 mono layers of potassium at 500 K has been studied by X-ray photoelectron spectr oscopy, ultraviolet photoelectron spectroscopy and change of work function measurements. It is found that potassium can diffuse into the substrate and react with antimony atoms in the GaSb surface. At low exposures oxygen pen etrates below the topmost layer, inducing a disruption of the K-Sb bonds an d reacting with potassium, antimony and/or gallium to form their correspond ing oxides (O2-). At th, same time, potassium atoms are gradually drown bac k to the surface with oxygen exposure. At higher exposure, potassium peroxi de (O-2(2-)) on the surface is observed follow the formation of the monoxid e K2O. The elevated temperature promotes oxygen diffusion into the substrat e and delays the appearance of potassium peroxide, resulting in an increase of the saturated adsorption of oxygen, and this is beneficial for further oxidation of the GaSb surface. (C) 1999 Elsevier Science B.V. All rights re served.