Ion beam erosion of graphite surfaces studied by STM: Ripples, self-affineroughening and near-surface damage accumulation

The surface topography of (0 0 0 1) highly oriented pyrolytic graphite erod ed by Xenon ions at an incidence tilted relative to the surface normal was measured as function of the tilt angle theta and the ion energy E and fluen ce Phi by means of scanning tunneling microscopy (STM). Up to about 10(1x) ions/cm(2), the formation of periodic ripple structures was observed. The s witching of the wave pattern from parallel to perpendicular orientation rel ative to the ion beam projection, as predicted for increasing tilt angle th eta, was confirmed. Moreover, the wavelength was round to scale with the ra nge and longitudinal straggling width of the collision cascade. This fact a llows a direct determination of the mean lateral size of the collision casc ade. The dependence of the measured wavelength on the three parameters thet a, E and Phi is reproduced by the theory of sputter erosion by Bradley and Harper. The high-fluence regime can be described by the Kardar-Parisi-Zhang theory (KPZ). (C) 2000 Elsevier Science B.V. All rights reserved.