Microwave CVD Thick Diamond Film Synthesis Using CH4/H2/H2O Gas Mixtures

Thick diamond films with a thickness of up to 1.2 mm and a area of 20 cm2 have been grown in a homemade 5 kW microwave plasma chemical vapor deposition (MPCVD) reactor using CH4/H2/H2O gas mixtures. The growth rate, radial profiles of the film thickness, diamond morphology and quality were evaluated with a range of parameters such as the substrate temperature of 700 oC to 1100 oC, the fed gas composition CH4/H2 = 3.0%, H2O/H2 0.0%∼ 2.4%. They were characterized by scanning electron microscopy and Raman spectroscopy. Translucent diamond wafers have been produced without any sign of non-diamond carbon phases, Raman peak as narrow as 4.1 cm-1. An interesting type of diamond growth instability under certain deposition conditions was observed in a form of accelerated growth of selected diamond crystallites of a very big lateral size, about 1 mm, and of a better structure compared to the rest of the film