Growth rate and structural characterization of diamond layers produced by CVD methods

Abstract

This paper discuss the effect of working gas pressure, changed in the range of 20-100 mbar, and hydrocarbon concentration, changed in the range of 2.3-3.0%, on the structural properties of polycrystalline diamond (PCD) films synthesized in a hot filament chemical vapor deposition (HFCVD) system. As a working gas the mixture of CH 3 OH diluted in H 2 was used. Characterization of CVD diamond were performed by using three most common techniques such as Scanning Electron Microscopy (SEM), Raman and X-ray diffraction (XRD), which have been intensively employed for characterizing CVD diamond layers. With increasing hydrocarbon concentration at each deposition pressure, the decrease of the diamond grain sizes was observed, accompanied with increasing sp 2 /sp 3 ratio. The pressure exerted has rather small influence on the film growth rate as it is indicated by diamond film thickness. Such pressure dependence of the diamond growth rate was suggested to result from two competing effects of pressure on the concentration of carbon radicals, responsible for diamond growth, close to the diamond growth surface.