Growth of high quality large grained diamond films on mirror-polished silicon without surface pretreatment

In this paper successful growth of continuous diamond films on mirror-polished (10 0) silicon substrate without any surface pretreatment for nucleation enhancement, were achieved using a 5-kW microwave plasma CVD reactor for the first time. A randomly oriented 235 mum and a <111> textured 220 mum thick high quality diamond films were obtained from CH4/H-2 and CH4/H-2/O-2 plasma by keeping other parameters unchanged, respectively. Scanning electron microscopy (SEM) micrographs show that both films have well-facet large grains with sizes comparable to the thickness. The average grain sizes can reach approximately 35% of the thickness, much larger than that of films grown with abrasion pretreatment (approximate to 10% of the thickness). The SEM micrograph of the cross-section clearly shows large grains were grown nearly directly from the bottom extended to the growth surface with a cylindrical columnar growth rather than usual cone-shaped columnar growth for films grown with surface pretreatment. Raman and Fourier transformer infrared spectroscopy were used to characterize phase purity and optical transparency of the films, respectively. The thermal conductivity of the films was also measured and discussed. (C) 2003 Elsevier Science B.V. All rights reserved.