Atomic force microscopy of (100), (110), and (111) homoepitaxial diamond films

We present atomic force microscopy images of diamond films grown by chemical vapor deposition epitaxially on diamond (100), (110), and (111) substrates. The films were grown from 0.2%–1.6% mixtures of CH4 and C2H2 in H2 in a hot-filament reactor at a total pressure of 25 Torr. The substrate and filament temperatures were held at 810–1000 and 2000–2150 °C, respectively. A (100)-oriented diamond film grown with 0.3% CH4 at a substrate temperature of 810 °C was rough on the μm scale, exhibiting pyramidal features, terraces, and penetration twins, while films grown at higher substrate temperatures and hydrocarbon flow rates were smooth on the nm scale and showed evidence of a (2×1) reconstruction. A (110)-oriented film was very rough on the μm scale but nearly atomically smooth on the 0.5–5 nm scale and exhibited local slopes higher than 40° with no evidence of faceting. A film grown on a diamond (111) substrate underwent spontaneous fracture due to tensile stress and exhibited a roughness of ≊10–50 nm on the ≊100 nm lateral scale in regions far away from any cracks. The implications of the morphological features for diamond growth mechanisms are discussed.