Gas discharge produced by millimiter wave beams and its application in CVD diamond technology

Abstract

Summary form only given. The paper reviews the results of studying continuous gas discharges generated by millimeter-wave radiation in wave beams. Features of localization of the continuous discharge, and plasma parameters are described. Application of the non-equilibrium plasma generated by beams of millimeter waves in the CVD (chemical vapour deposition) diamond technology is analyzed in detail. It is shown that higher microwave frequencies in CVD reactors, as compared with the frequencies 2.45 GHz and 0.915 GHz used conventionally, cause the gas medium get activated faster, i.e. increase the rate of production of atomic hydrogen and other chemically active radicals. As the result, diamond films are deposited in CVD reactors with higher-frequency microwaves at a faster rate as compared with traditional reactors. The presentation demonstrates the potentials of a plasma CVD reactor with millimeter-wave radiation taking a novel MPACVD reactor based on the 20 kW/30 GHz gyrotron as an example. In the developed CVD reactor the following conditions of the diamond coating process are carried out simultaneously: the deposition rate is higher than 10 mum/h, the size of diamond film area is larger than 100 cm2 and diamond films with high thermal conductivity and optical transparency are grown