Characterization of GaAs(111) surfaces by AES and LEED

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Abstract
A quantitative Auger formalism which allows us to predict the composition of GaAs(111) surfaces with any combination of Ga and As atoms in the outermost bilayer is presented, and applied to the study of (111) surfaces prepared by different combinations of ion bombardment and annealing (IBA), as well as by simultaneous ion bombardment and annealing (SIBA). The formalism predicts the coverage of the only structure quantitatively determined, GaAs(111) 2×2-Ga, and of all the structures reported in the literature for the (111) surfaces. By a SIBA (Ar, 0.6–1 kV, 870 K) treatment, we have obtained for the first time a 2×2 superstructure on the (1̄1̄1̄)As face, corresponding to 1/4 of an As monolayer in the first layer. The effect of the different methods of preparation has been studied by the interaction of the corresponding surfaces with oxygen. The (1̄1̄1̄)As surfaces prepared by SIBA present a sticking coefficient smaller than those obtained on any (111) surface prepared by IBA. Consequently, the sticking coefficient seems to depend strongly on the method of surface preparation, but much less on the degree of saturation of the dangling bonds on Ga atoms of the first layer, as suggested before.

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