Texture formation in polycrystalline diamond films

Structure and morphology of polycrystalline diamond films prepared by chemical vapor deposition (CVD) have been studied using x-ray texture analysis, angle-resolved optical reflection, and scanning electron microscopy. The films under investigation exhibit a pronounced 110 fiber texture, i. e. , a preferential alignment of 110 planes perpendicular to the growth direction. By thinning a 180-μm-thick CVD diamond film in an oxygen discharge the dependence of the degree of 110 texture on the film thickness has been investigated. It was found that the crystals formed at the beginning of the film growth are randomly oriented, and that a preferential orientation of 110 planes develops with increasing film thickness. Computer simulations show that this behavior can be explained by evolutionary selection, i. e. , competing growth of differently oriented crystals, which implies that 〈110〉 is the direction of fastest growth. In addition, angle-resolved optical reflection and scanning electron micrographs show that the surface of the diamond films consists of 111 faces. Possible explanations for these findings are discussed.