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Mechanism of oxidation of the GaAs(001) surface: (a) Initial oxidation, vertical growth of the oxide layer; (b) oxidation of the inner layer: stress accumulation at the interface; (c) stress release by a Ga atom ejection into the oxide layer with a vacancy generated at the interface; (d) filling of the vacancy by a neighboring atom and formation of an As antisite defect (As, Ga, and O atoms are depicted by white, black, and gray balls, respectively).
An atom ejection event during the oxidation: the z-projection the trajectory of a Ga atom ejected in the above amorphous oxide layer is shown (black curve), compared with the trajectory of a nonejected one, whose fluctuations indicate thermal vibrations within the oxidizing layer.
Computed electronic DOS for the reconstructed GaAs(001) surface (dashed line), an oxidized surface before atom ejection (gray line), and after the occurrence of such event (black line). Energy levels are introduced in the bandgap by the formation of structural defects at the interface during the oxidation; is the GaAs valence band edge.
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