Abstract
Carbon nitride films have been prepared by ion-beam-assisted deposition, in which carbon was evaporated by electron beam and nitrogen and/or argon ions were simultaneously bombarded onto silicon substrate. The influences of the argon ion addition on the surface roughness, the nano-indentation hardness and the friction coefficient of carbon nitride films are investigated. Furthermore, the composition and the chemical bonding states of carbon nitride films are analyzed by Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. Even in the films prepared at the ion beam gas ratio (Ar/N2) of 1, argon concentration was about 2at% although around 30at% nitrogen was incorporated. Nano-indentation studies show that argon ion addition in the film formation process below 100°C lead to the higher hardness of the film and that the maximum hardness was 23GPa. Furthermore, argon ion addition was effective for reducing the friction coefficients of the film against a steel ball. Nls peaks in XPS spectra indicate that population of nitrogen surrounded by three carbon in the C-N network, which corresponds to C-N cluster formation, increased by argon ion addition. Therefore, the improvements of the mechanical properties of the films are thought to be induced by the C-N cluster formation promoted by argon ion addition at low temperature.
