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 t...

Texture formation in polycrystalline diamond films

http://navier.engr.colostate.edu/pubs/DiamRelatedMater_4_1173_1995.pdf

Studies on nucleation process in diamond CVD: an overview of recent developments

Diamond and diamond-like films

The surface energies for 24 surfaces of diamond structure cubic crystals of C, Si and Ge have been calculated using the modified embedded-atom method. The results show that the three lowest surface energies correspond to the (111), (211) and (433) surfaces. Considering surface energy minimization solely, the (111), (211) and (433) textures should be favourable successively in diamond cubic films. The appearance of abnormal grains or textures with (111) and (211) orientations in Si, Ge and C films results from surface energy minimization.

Anisotropy analysis of the surface energy of diamond cubic crystals

The seeding for large‐area mosaic diamond films approaching single‐crystal quality is described. The technique includes patterned etching of relief structures in Si substrates, deposition from a slurry and orientation of macroscopic diamond seed crystals in the structures, and chemical vapor deposition overgrowth of the diamond seeds to form a continuous film. The film comprises ∼100 μm single crystals, which are separated by low‐angle grain boundaries of a few degrees or less. We believe that these low‐angle grain boundaries will not affect the electrical properties of majority‐carrier devices.

Large‐area mosaic diamond films approaching single‐crystal quality

A technique has been developed to grow (111) textured diamond films on smooth substrates using attached diamond seeds. The degree of texture is defined by the initial texture of the seeds. This initial texture depends upon the seed size and the cleaning procedure. Under the best conditions, over 90% of the seeds exhibit a (111) texture with a tip angle of less than 0.25°. Further growth of diamond on these seeds does not affect the texture, and diamond films obtained by such growth are expected to have smoother surfaces and more controlled doping than nontextured polycrystalline films.

M. W. Geis

Papers

Growth of textured diamond films on foreign substrates from attached seed crystals