Microstructure And Properties Of CN_x Films Deposited By DC Bias Enhanced Pld Technique

CNx films have received considerable interest from a larger number of researchers for their excellent properties, but it still doesn’t get further application attributed to lower N atomic percentage and chemical bonding structure. Selecting bias voltage techniques would be feasible to improve the content of sp3bonding and N atomic percentage in the films. However, there is very few reports about CNx films prepared by bias voltage assisted pulsed laser deposition.The fabrication of CNx films grown on silicon surface by graphite target and pulsed laser deposition technique (i.e.c-CNx) at various bias voltages were reported in this paper. The surface morphology, chemical composition, chemical bonding structure and mechanical properties of the films were systematically characterized. We also investigated the relationships among bias voltage, structure, and mechanical properties including hardness, cohesion and friction. Then we make further study on the CNx films (i.e. i-CNx) deposited by bias voltage assisted pulsed laser deposition, which select rich-nitrogen and rich-sp3bonding carbon nitride as target instead of graphite. In view of the analysis between c-CNx and i-CNx, finding the optimum parameters are applied to achieve the maxmum of N incopration and sp3bonds combination, and meanwhile the connection between chemical bonding and mechanical properties also have been in-depth analysised.The microcosmic morphology, chemical composition and chemical bonding structure of the two group films including c-CNx and i-CNx films were characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and Raman spectroscopy (Raman) respectively. The relative mechanical properties have been observed by using nano indentation, coating scratch tester automatically and a ball-on-disk tribometer. The results show that all films are comprised of various nano-particles and the homogeneity of films has small changes with various bias voltages. Particllarly bias voltage assisted pulsed laser deposition could sharply improve the content of N percentage. By contrastive analysis of XPS and Raman datas, xsp2/xsp3and xsp2C-N/xsp3C-N of two group films decreased firstly and then increased, attaining the minimum values at Vb=-40V(c-CNx films:2.43and1.76; i-CNx films:1.78and1.39). Meanwhile, the minimum ID/IG is2.2for c-CNx and1.6for i-CNx films were obtained under the same bias voltage. It concluded that Vb=-40V is the optimum conditions for the combination of sp3bonds. The tendency of hardness well agrees with the changes of xsp3and xsp3C-N-With the increase of bias voltage, the adhension strength appears a trend of augment between c-CNx films and i-CNx films. The friction coefficient variation can be attributed to the uniformity of the films surface affected by bias voltage. The better the smoothness of the surface, the lower the friction coefficient.