Properties of amorphous a-CH(: N) films synthesized by direct ion beam deposition and plasma-assisted chemical vapour deposition

Hydrogenated carbon films and hydrogenated carbon films containing nitrogen have been synthesized by direct ion beam deposition (IBD) using cyclohexan e and methane as precursors and by plasma-assisted chemical vapour depositi on (PACVD) using cyclohexane and acetylene as precursors. The elemental com position has been assessed by gas chromatography. The films' structure has been analysed by FTIR, Raman, NEXAFS spectroscopy and X-ray reflectivity. T he hardness has been determined by nanoindentation and microhardness measur ements, and the stress by optical profilometry. FTIR measurements reveal an increasing nitrile and amine group absorption w ith a corresponding decrease of C-H stretching modes as the nitrogen concen tration in the film increases. The nitrogen-containing functional groups ar e proposed to be at peripheral positions of graphitic domains. The correspo nding reduction of the domain size is detected in the Raman data, and the i ncrease of delocalized bonding in a-CH(:N) films with respect to a-CH films is confirmed by the NEXAFS results. In the carbon K-edge spectra, the inte nsity of the pi* C=C resonance at similar or equal to 285.3 eV has been fou nd to increase as a function of N content. This indicates principally an in crement of the sp(2) hybridization. Such a structural change leads to a dec rease in the hardness and the internal compressive stress with respect to a -CH films. In a film containing 15 at% N, the hardness is reduced to 44% an d the stress to 36% of that for a-CH. (C) 1999 Elsevier Science S.A. All ri ghts reserved.