Preparation of diamond film by dc thermal plasma torch

A dc thermal plasma system has been designed and constructed to obtain diamond films from a mixture of CH4 and H2. The effects of the deposition conditions such as substrate temperature (850 C - 1050 C), gas mixing ratio (0.5 - 1.5 percent CH4 in H2), chamber pressure (50 - 200 torr), axial magnetic field (0 - 900 Gauss) on the diamond film properties such as morphology, purity of the film and deposition rate, etc., have been examined with the aids of scanning electron microscopy, X-ray diffraction and Raman spectroscopy. Under optimum conditions, high quality diamond films can be obtained with high deposition rate (more than 1 micron/min). Both the growth rate and particle size increased with the substrate temperature but the morphology changed from the faceted to unshaped when the temperature deviates from its proper range. Furthermore, higher growth rates of 1.5 micron/min can be obtained by applying an axial magnetic field to the plasma torch. The observed values of interplanar spacings of diamond were in a good agreement with the values reported in ASTM data and all deposits have the diamond peak of 1332.5 cm in the Raman spectra.