Observation of C film formation on a highly oriented pyrolitic 60 graphite substrate via scanning tunnelling microscopy

We have investigated the early stages in the adsorption process of C60 molecules on a highly oriented pyrolitic graphite HOPG.substrate. C60 powder was thermally evaporated in UHV of 10y8 Pa conditions onto a freshly cleaved HOPG surface. We did not observe individual fullerenes on the substrate for the case of short deposition times and low evaporation rates. However, small islands of C60 molecules with an fcc structure could be observed when the deposition rate was about 0.2 nmrmin and the total thickness was above 1 nm. The islands did not grow in the vicinity of the HOPG steps. The typical lateral dimensions of these islands were of the order of a few hundred square nanometers, having thickness of up to five monolayers. We modified the shapes and positions of these islands by the STM tip, using a small less than 1 V.bias voltage. q1999 Elsevier Science B.V. All rights reserved