CARBON-BASED HARD FILMS PRODUCED BY HIGH-TEMPERATURE CARBON-ION IMPLANTATION

We have performed 120 keV carbon-ion implantations into copper at high doses (5 x 10(17) cm(-2)) and high temperatures (973 K less than or e qual to T less than or equal to 1273 K) acid characterized the microst ructure of the surface layer formed by this process. This study reinve stigates the possibility of producing thin diamond films by the so-cal led carbon-ion-implantation-out-diffusion method. The basic mechanisms of the carbon layer growth are not well understood and we propose a m odel where the segregation of C atoms and the preferential sputtering of Cu atoms would play an important role. In order to examine the vali dity of such a hypothesis we have investigated the influence of both t he ion flux and the temperature. For all experimental conditions we ob serve the formation of a uniform graphite layer (turbostratic graphite ) with a more- or less-pronounced texture along the (0001) direction. We have identified in the graphite layer a high density of graphitic s helled micrograins (''fullerene onions'') but the presence of diamond has never been detected. Our results are in agreement with some previo us studies on this subject that were not able to reproduce the first r esults claiming that diamond formation is possible by this method. It is suggested that a higher C ion flux or the presence of impurities in the copper substrate could be favourable for such a mechanism of diam ond growth.