Damage creation in α-Al2O3 by MeV fullerene impacts

Single crystals of alpha-Al2O3 were irradiated at room temperature with C-60 clusters at normal and grazing incidences. The extent of the induced damage was determined using Rutherford backscattering spectrometry in channeling geometry (RBS-C), A damage cross-section of 3.1 x 10(-12) cm(2) was obtained for the highest electronic stopping power (76.2 keV nm(-1)). From electron microscopy observations continuous amorphous tracks were evidenced around the projectile trajectory and an electronic stopping power threshold for damage creation of 18 keV nm(-1) was also determined. The spatial correlation in depth of the cluster components were deduced from both direct track length measurements and the damage profiles extracted from RBS-C analysis. The maximal correlation length represents about one-third of the projected range (R-p) of a free carbon. Using atomic force microscopy (AFM), conically shaped hillocks corresponding to the out of plane expansion of the latent tracks were observed. These structures characterize nanometric changes of the plastic properties of sapphire induced by high electronic excitations. (C) 1998 Elsevier Science B.V. All rights reserved.