High Fluence Ion Irradiation of Thin Fullertte Films

Abstract

Thin fullerite films - partly covered with a thin Au layer -have been irradiated with 100 keV Arn+ (n = 1, 6, and 12), 250 keV N+, and 30 keV Au+ ions up to high fluences, and subsequently analyzed by profilometry, Rutherford Backscattering Spectrometry (RBS), and Atomic Force Microscopy (AFM). Depending on the system, either an increase or a decrease of the film thickness after the irradiations was found, and the probing RBS α particles suffered sometimes an enhanced, and sometimes a reduced energy loss upon passage through the films. The comparison of profilometry and RBS results on uncovered and covered samples allows us to separate the different effects which influence the behavior of high-fluence irradiated fullerite samples clearly from each other. Such effects might be the incorporation of the projectile ions, density changes, phase changes, sputtering, and transport of neighbored unirradiated matter into the irradiated zone. It is remarkable that ion irradiation of fullerite can lead as well to a densified material, with densities of about 2.1 g-cm−3, as to a foam-like carbonaceous material with a density around 0.35 g-cm−3 - depending on the type of projectile and its range. The latter case appears to be characteristic for high-fluence heavy noble gas implantation into fullerite. Fullerite sputtering was reconfirmed to decrease inversely with the fluence.