Carbon nitride thin-films deposited from coupled r.f.-magnetron sputtering and ion beam-assisted processes

Amorphous carbon nitride thin-films (a-CN) have been prepared in a hybrid plasma-based deposition process that allows independent control of nitrogen ion bombardment, by combining r.f.-magnetron sputtering of a graphite target with simultaneous nitrogen-ion-beam assistance from a capacitively coupled r.f, ion source. The films were deposited on unheated silicon substrates at 0.3 Pa of total pressure, using Ar and N-2 gas flows of 3 and 1 seem, respectively. The increase in nitrogen ion energy from 140 to 800 eV, leads to a reduction of both the deposition rate (from 4.4 to 1.6 nm/min) and the nitrogen to carbon ratio in the films (from 0.26 to 0.17), which suggested chemical sputtering of deposited material by the impingement of energetic nitrogen atoms. In addition, changes in the film structure and nitrogen-bonding configuration were also induced with the increasing in ion energy, as revealed by X-ray photoelectron spectroscopy and Raman analysis. Preliminary nanoindentation and pin-on-disk tests indicated the films are relatively hard (19 GPa) and with low friction coefficients (between 0.1 and 0.2) measured in air ambient. (C) 2001 Elsevier Science B.V. All rights reserved.