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

The surface topography of (0 0 0 1) highly oriented pyrolytic graphite eroded 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 fluence 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 switching of the wave pattern from parallel to perpendicular orientation relative to the ion beam projection, as predicted for increasing tilt angle theta, was confirmed. Moreover, the wavelength was round to scale with the range and longitudinal straggling width of the collision cascade. This fact allows a direct determination of the mean lateral size of the collision cascade. The dependence of the measured wavelength on the three parameters theta, 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.