(NH 4) 2S x - treated GaAs surfaces studied by soft x - ray photoelectron spectroscopy and S K - edge XANES

Abstract

The sulfur chemical bonding states on (NH 4) 2S x - treated GaAs surfaces have been studied by S1s core - level photoelectron and S K - edge fluorescence yield x - ray absorption near edge structure (XANES) using synchrotron radiation soft x - rays. The change in the sulfur chemical bonding states caused by annealing in vacuum after (NH 4) 2S x - treatment was confirmed more clearly by spectral changes in both spectra than in the S2p photoelectron spectra. While four kinds of sulfur bonding states exist on the as - treated surfaces, only the SGa bonding state was detected on the surface after annealing. The spectra of S1s photoelectron and S K - edge XANES both suggested that annealing after the (NH 4) 2S x - treatment is indispensable to achieve GaAs surface termination by SGa bonds.