Properties and structures of diamond-like carbon film deposited using He, Ne, Ar/methane mixture by plasma enhanced chemical vapor deposition

Diamond-like carbon (DLC) films have been deposited by a magnetically enhan ced plasma (MEP) chemical vapor deposition (CVD) system. The properties and structures of DLC films deposited by MEP-CVD using various gases (methane, He/methane, Ne/methane, and Ar/methane) were studied. The mechanical prope rties in terms of hardness, Young's modulus and stress, and optical propert ies in terms of optical band gap and refractive index were enhanced by addi ng inert gas in methane plasma. The magnitude of the effects on the propert ies for various inert gases was found as Ne, Ar, and He, on the surface rou ghness was found as Ar, Ne, and He. The Raman characteristic shows a depend ence of the bias voltage and inert-gas/methane ratio, as well as the inert gases dilution. The Raman spectroscopy analysis indicates that the changes of properties of the DLC films are due to the structural changes, such as s p(2) and sp(3) content in the films prepared under various deposition condi tions. The films deposited in Ne/methane show the lowest disordered (D) pea k to graphitic (G) peak intensity ratio, the D and G peak positions; highes t stress, hardness, Young's modulus, optical band gap, and lowest reflectiv e index. The films deposited in Ar/methane show the lowest surface roughnes s. This was proposed due to the optimum balance in the inert gas ionization potential and atomic mass. (C) 2000 American Institute of Physics. [S0021- 8979(00)02511-1].