Investigation on the influence of the gas flow mode around substrate on the deposition of diamond films in an overmoded MPCVD reactor chamber

Abstract

In an overmoded home-made MPCVD reactor, the influence of gas flow mode on the deposition of diamond films was investigated with H2/CH4 gas mixtures at the microwave power of 5800 W. The simulation results show that the diamond films can be grown in the environment filled with the gas mixture with relative high gas flow rate when an improved gas flow mode is established around the substrate. The scanning electron microscope and Raman spectra indicate that the improved gas flow mode plays a role in the growth of well-faceted crystals at the edge area of the diamond films. The quality, growth rate and uniformity of the diamond films can be significantly improved when introducing the improved gas flow mode. To explain the experimental results, the plasma is measured by optical emission spectrometer. It is shown that in the improved gas flow mode, the activated species of C2 and H in the plasma exhibit a uniform distribution. Furthermore the improved gas flow mode enlarges the area of the region where the concentrations of activated C2 and H are coupled. The diamond films with 50.8 mm and 101.6 mm in diameter have been finally deposited in the improved gas flow mode.