Surface sink effects on void formation in GaSb and InSb under ion irradiation

Abstract

Cellular defect structure forms on GaSb, InSb and Ge surfaces irradiated with energetic ions. These structures are generated after void formation via the movement of point defects induced by ion irradiation. In this transmission electron microscopic study, void formation by thin foil irradiation (irradiation after polishing for transmission electron microscopy (TEM)) was compared with void formation by bulk irradiation (cross-sectioning after ion irradiation), in order to investigate the effect of surface sinks for the point defects. The voids formed in GaSb and InSb by thin foil irradiation with 60keV Sn- at a temperature of 100-150K were smaller than those formed by bulk irradiation. The diameters and densities of the voids increased rapidly as the ion dose increased from 1 × 1014 to 2 × 1014 ions/cm2 under both types of irradiation. Amorphous halos were observed in the selected area diffraction patterns (SAED) of the thin foil irradiation specimens in addition to the main spots of the zincblende structure at a dose of 1 × 1014 ions/cm2. This finding contrasts with the polycrystalline ring patterns observed in the SAED of the bulk specimen under the same dose. It was concluded that the easy escape of interstitials to the surface assists both void formation and amorphization in thin foil irradiation. © 2008 The Japan Institute of Metals.