Studies of defects and impurities in diamond thin films

Diamond thin films were grown on silicon substrates using microwave plasma chemical vapour deposition at various microwave power densities (MPD). Three sets of the films were grown for various thicknesses. The films were characterised using micro-Raman spectroscopy, photoluminescence (PL), cathodoluminescence (CL) and X-ray photoelectron spectroscopy (XPS). Elastic recoil detection analysis (ERDA) was used to determine concentrations of light impurities (N and O), Micro-Raman spectroscopy shows a systematic variation in the non-diamond to diamond carbon content with MPD, Various defect centers related mainly with nitrogen were observed in PL and CL spectra of the films. A sharp feature was observed at 1.68 eV in all the spectra. This peak is attributed to Si impurity in diamond films. Interestingly, the intensity of the peak increases with increase in MPD, The broad band A in the CL spectra has contributions from both green and blue regions, and the intensity ratio of the green to blue region varies with MPD. The spectra of the films of various thickness were also compared, and it was found that the Si content of the films decreases with increasing thickness. ERDA results indicate that the films contain 0.1-0.6% N and O as impurities. The interface composition of the films as a function of MPD was investigated using XPS, and the increase in the Si content of the films was correlated with the change in composition of the diamond/silicon interface. (C) 1998 Elsevier Science S.A.