Abstract

LEED, HEED and Auger spectroscopy were combined with mass spectrometric studies of Ga and As 2 molecular beam interactions with GaAs (100) and (1̄1̄1̄) surfaces. It was found that surface structural changes could be correlated with gain or loss of As 2 from the surface. A kinetic model involving changes in surface stoichiometry is proposed which gives quantitative agreement with experiment for both desorption rate and surface composition. The model assumes that As 2 is adsorbed in a weakly-bound molecular precursor state from which dissociation into As atoms in As surface sites occurs. Recombination of surface As atoms into the molecular state occurs at a rate whose activation energy decreases rapidly with increasing As concentration in the surface.

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