Electronic structure and hardening mechanism of Si-doped/undoped diamond-like carbon films

摘要

In this article, we have investigated the electronic structures of silicon-doped and undoped diamond-like carbon (DLC) thin films using Fourier transform infrared (FTIR) spectra, Raman spectra, photoluminescence (PL), and X-ray absorption near edge structure (XANES) spectroscopy. The films were deposited by Plasma-Enhanced Chemical Vapour Deposition (PECVD) method in argon atmosphere using C_2H_2 and/or Si(CH_3)_4 vapour precursors. Raman spectra displayed a decrease in (I_D/I_G) ratio for films synthesized using Si(CH_3)_4 vapour, indicative of the formation of more diamond-like (sp~3 rich) films. The PL intensities and the full width at half maximum (FWHM) of the PL band increased, whereas PL peak position shifted towards lower energies when the Si incorporation was increased in the film. FTIR spectra revealed an increase in Si-H_n and C-H_n bonding intensity at 2100 cm~(-1) and 2900 cm~(-1), respectively, with increased Si incorporation. Hardness as well as the Young's modulus changed with not only the sp~2 content present in the film, but also decrease in the three-dimensional interlinks of the C-C atomic bond structure by the C-H_n and Si-H_n weaker bonds.