Latent tracks in sapphire induced by 20-MeV fullerene beams

摘要

Single crystals of alpha-Al2O3 were irradiated with 20-MeV fullerene beams in a fluence range from 1.0 x 10(10) to 22 x 10(11) C-60(+) cm(-2). The cluster electronic stopping power (dE/dx)(e) was approximately 62 keV nm(-1). Two complementary techniques were employed to assess the modifications induced by these irradiations: Rutherford-backscattering spectrometry in channeling geometry (RBS-C) and transmission electron microscopy (TEM). The disorder induced by electronic processes is clearly determined by the RBS-C analysis. A damage cross section A(e) of about 2.2 x 10(-12) cm(2) has been extracted from the disorder kinetics, which corresponds to a track radius of approximate to 8.5 nm. From lattice-disorder profiling, a maximal decorrelation length of the C-60 clusters in the crystal was estimated to be approximate to 150 nm. TEM micrographs exhibit cylindrical latent tracks formed around the projectile trajectory, while the high-resolution observations evidence the amorphization of sapphire in the core of these tracks. The present results have been interpretated within a model of high locally deposited energy densities in the cluster irradiation regime. [References: 24]