Diamond and Related Materials, 2 (1993) 1257 1262 1257 Non-diamond carbon phases in plasma-assisted deposition of crystalline diamond films: a Raman study* M. Silveira, M. Becucci** and E. Castellucci European LaboratoryJbr non-Linear Spectroscopy (LENS) Largo E. Fermi 2, 50125 Firenze (Italy) and Dipartimento di Chimica, Universitgt di Firenze, via G. Capponi 9, Firenze (Italy) F. Polla Mattiot, V. Barbarossa, R. Tomaciello and F. Galluzzi Eniricerche S.p.A., 00016 Monterotondo Scalo, Roma (Italy) (Received August 31, 1992; accepted in final form December 7, 1992) Abstract The micro-Raman technique has proved helpful in the analysis of diamond samples grown on silicon substrates by PA-CVD. With different deposition conditions and substrate preparation, isolated grains or continuous films both containing non-diamond carbon phases as major impurities were obtained. These can be distinguished spectroscopically from pure diamond structures as they show broad features peaked at different frequencies with respect to the diamond Raman line. Non-diamond carbon phases were investigated as a function of deposition parameters and silicon substrate pre-treatment. By deconvolution of the Raman spectra the content of non-diamond carbon phases has been estimated to be 2% for isolated crystals grown on unscratched substrates and as much as 10% for continuous films (small crystallites with extended grain boundaries). 1. Introduction In the metastable growth of diamond by CVD meth- ods (see ref. 1 for a review) non-diamond carbon phases can often be found. Their presence introduces a degrada- tion of the physical properties of the material, which is particularly detrimental in optical and electronic applica- tions [2]. Raman scattering is very well suited for the character- ization of carbon phases, owing to its ability to distin- guish between sp 3 and sp 2 carbon bonds and between crystalline and amorphous regions [3-5]. Moreover, by using a micro-Raman technique, useful information can be gained on the distribution of the different forms of carbon in the grains and films of diamond [6-7]. Here we submit a Raman micro-spectroscopic study of non-diamond carbon phases present in crystalline diamond depositions, grown on silicon substrates by microwave plasma-enhanced CVD. We investigated, in particular, the role of substrate pre-treatments and deposition parameters on the occurrence and on the structure of non-diamond components and attempted to give a quantitative evaluation of the graphitic content by comparison of the integrated areas of the calculated *Paper presented at Diamond 1992, Heidelberg, August 31- September 4, 1992. **Author to whom correspondence should be addressed. Raman bands obtained after deconvolution of the mea- sured spectra. Reasonable assumptions as to the assign- ment of the Raman frequencies to different carbon phases were taken from the literature. 2. Experimental methods The growth of polycrystalline diamond was carried out in a standard ASTeX microwave assisted chemical vapor deposition system. Microwave (2.45 GHz) power level, total flow and pressure in the reactor were kept constant in all experiments at l l00 W, 500 sccm and 40 Torr respectively. Methane content was 1% and 2% in hydrogen and molecular oxygen, when added, was 1%. The diamond films were deposited on monocrystalline (100) silicon substrates heated to 860 °C, and a hydrogen plasma was allowed to act on them for 10 min before the deposition run. Standard deposition time was 8 h. Pre-treatments of silicon wafers consisted of polishing with diamond abrasive paste or ultrasonic cleaning in a diamond powder colloidal solution. Non-pre-treated and A1203 powder scratched substrates were also used in this study. Preparation conditions for each sample are summarized in Table 1. Scanning electron microscopy (SEM) images of depos- ited diamond films were taken with a Cambridge Stereo Scan 360. 0925-9635/93/$6.00 ~) 1993 - - Elsevier Sequoia. All rights reserved