Two-step diamond growth for reduced surface roughness

A two-stage growth process proposed by Wild et al. (Diamond Relat. Mater., 2 (1993) 158-168) and demonstrated in earlier work (C. Nørgård, A. Matthews and S. Eskildsen, Surf. Coat. Technol., 74-75 (1995) 358-361) has been used to obtain smooth {100}-faceted diamond films. By controlling the growth parameter α, i.e. the ratio of the growth rates on {100} and {111} faces, during deposition, it is possible to obtain smooth diamond films with a minimum film thickness for complete coverage of {100} faces which is considerably thinner than for conventional 〈100〉-textured films. The deposition method utilized is a hot filament CVD chamber with a CH₄-H₂ gas mixture. In the first stage, a highly 〈100〉-textured diamond film is grown, which results in a relatively rough surface with small {100} faces compared with the film thickness. The second stage involves subsequent diamond deposition with growth parameters which increase the growth rate of the inclined {111} planes of the 〈100〉-textured film. The {100} faces of the diamond crystal then expand and eventually grow together to form a smooth surface. Due to a poor 〈100〉 texture after the first step, only a limited decrease in surface roughness is observed.