ION IMPACTS AND NANOSTRUCTURES ON GE(111), IN0.22GA0.78AS GAAS(100) AND ALPHA-QUARTZ SURFACES OBSERVED BY ATOMIC-FORCE MICROSCOPY/

Atomic force microscopy (AFM) is used to compare the topography of the ion-bombarded surfaces of Ge(111), atomically flat terraces on strain ed layers of In0.22Ga0.78As on GaAs and alpha quartz. Germanium sample s were bombarded with 100 keV Ge+ ions at doses of up to 10(16) ions c m(-2). A cellular structure with a mean pore diameter of 50 nm was obs erved at greater detail but similar to that reported in earlier scanni ng electron microscope (SEM) measurements [I. H. Wilson, J. Appl. Phys . 53, 1698-1705 (1982)]. It is proposed that this structure is formed by the intersection of the etched surface with point defect clusters c reated in the dense collision cascade, and the combined effects of spu tter etching, ion reflection and redeposition. Individual impact crate rs are observed on As+- and B+-bombarded In0.22Ga0.78As/GaAs (35 keV, 10(11) ions cm(-2)) at the areal density identical to that of ion impa cts. The craters arising from As+ bombardment are attributed to damage associated with nuclear stopping in the primary collision cascade. By contrast, alpha quartz samples bombarded with a wide range of ions (P b, Ni, O, Si, Ar and In at doses of 10(10)-10(11) ions cm(-2)) and ene rgies (30 keV to 0.73 GeV) exhibit asperities (bumps). In the case of very high energy ions, the areal density of asperities is much less th an that of ion impacts. The asperities are attributed to volume expans ion associated with amorphous zone creation. In the case of very high energy ions, zone creation is attributed to energetic knock-on cascade s directed back towards the surface.