MODELING OF CHEMICAL VAPOR DEPOSITION OF DIAMOND FILMS FROM ACETYLENE-OXYGEN FLAMES

摘要

The production of artificial diamond and diamond layers is not only of scientific but also of commercial importance. Techniques allowing for high growth rates of large and homogeneous diamond films are of special interest. Chemical vapor deposition of diamond layers using rich acetylene-oxygen flames as the source for carbon atoms is a promising step toward this goal. In the present paper, a detailed surface reaction mechanism for the homoepitaxial growth of a diamond layer is presented. Numerical results based on a one-dimensional stagnation-point flow to describe the flame above a surface are presented and compared with experimental data from the literature. Growth rates as well as species distributions in the gas phase are shown. The surface mechanism is based on earlier work by Harris and Goodwin but has been extended significantly. Growth is allowed to take place only at surface steps, and reactions are included to describe the addition of CH_2 and CH radicals as well as carbon atoms at the surface. In low-pressure acetylene-oxygen flames, CH_3 radicals and carbon atoms are equally important for the growth process. A key feature is the extension of the mechanism by O_2 molecules and O atoms, leading to the oxidation of the diamond layer. With this extension, the model describes diamond-growth rates as a function of the temperature of the substrate and the composition of the unburned gases within a factor of 2.