Surface structures of clean and sulfur-treated GaP(111)a studied using AES, LEED, and STM

Abstract

Surface structures of clean and sulfur-treated GaP(111)A have been studied by Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). A GaP(IIl)A surface is reconstructed into a 2x2 structure by Ar ion sputtering and annealing at 4500C. The 2x2 structure is for the first time imaged by STM. A surface structure model for the structure is discussed in terms of the cation-vacancy model. The sulfur-treated surface shows a 1X1 LEED pattern and the relative AES intensity of sulfur remains constant between 200-5000C. The coverage of sulfur on the GaP(111)A surface is estimated to be about 0.82 monolayers. The sulfur is desorbed at about 5500C where the LEED pattern was changed into a facet-like one. The different surface reconstructions (1X1-S and 2x2-S) on sulfur-treated III-V compound semiconductor (111)A surfaces are discussed in terms of the bond strength. © 2009 The Surface Science Society of Japan.