X-ray photoelectron diffraction studies of zinc selenide

Polar and azimuthal angle‐resolved XPS studies of ZnSe layers grown epitaxially on {100} GaAs by H2 transport of the elements are described. Comparison of the polar X‐ray photoelectron diffraction (XPD) patterns obtained for rotation about [110] and [110] axes confirms the dominant influence of structural factors in determining the shape of the patterns. Azimuthal XPD patterns are shown to reflect symmetry properties directly related to the emitting sites, and their use to determine the symmetry of an exposed single‐crystal surface is demonstrated. The outermost ∼100 Å of all the ‘as‐grown’ ZnSe layers were ∼20–35% Zn rich. Ar ion bombardment (800 eV, ∼5 μA) rapidly restored the surface stoichiometry to within 10% of 1:1. The disorder concurrently introduced resulted in XPS peak broadening without impairment of the polar XPD pattern. Annealing at 300°C in high vacuum removed the disorder without affecting either the stoichiometry or the XPD pattern. It is inferred that split‐ interstitials are the preferred sites both for atoms displaced by ion bombardment and for the excess Zn initially present.