Estimation of low-energy ion bombardment damage on GaAs(001) surface by x-ray photoelectron diffraction

The structural damage on a GaAs (001) surface was estimated by means of X-ray photoelectron diffraction (XPED), which was induced by 170 - 1200 eV ion bombardment at various polar angles of ion-incidence. The thickness of the damage, which was saturated at a sufficiently high ion dosage, was obtained using a 'homogeneous two-layer model'. The saturation thickness, which varied from 4 to 36 A, decreased as the ion acceleration voltage decreased and the polar angle of ion incidence increased. In the state before saturation, a 'mosaic two-layer model' was applied, and the results indicated that the initial rate of the damage formation of the ion bombardment depended on the ion acceleration voltage and the angle of ion-incidence. The 'displacement yield', i.e., the number of displaced atoms produced by one ion, was obtained. (author)