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 cm(2) have been grown in a homemade 5 kW microwave plasma chemical vapor deposition (MPCVD) reactor using CH4/H-2/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 degrees C to 1100 degrees C, the fed gas composition CH4/H-2 = 3.0%, H2O/H-2 = 0.0% similar to 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.