A study on surface morphologies of (001) homoepitaxial diamond films

A systematic study on surface morphologies of (001) homoepitaxial diamond films prepared by microwave plasma-assisted chemical vapor deposition indicates that growth of these films strongly depends on deposition parameters such as misorientation angles of substrates, methane concentrations, and growth temperatures. With increasing the misorientation angles; the surface morphologies changed from growth hillocks to macrosteps. Step-flow growth resulted in higher growth rates than hillock growth. These indicate that surface steps play a significant role in diamond growth. It is proposed that hillock growth occurs through two-dimensional nucleation on terraces when the density of surface steps is low, while the step-flow growth proceeds along the [110] directions on the substrates with the high density of steps. Homoepitaxial growth at 1% CH4 produced macrosteps with the surface close to the single-domain structure, while at 2 and 6% CH4, growth hillocks and random growth morphology occurred with the double-domain surface. The variation of surface morphologies and structure with methane concentration is attributed to lower mobility and shorter diffusion length of adsorbates on the surface at higher methane concentrations. During the step-flow growth, step bunching was more apparent at a lower temperature of 875 than at 1200 degrees C. Step-flow growth with the single-domain surface is believed to produce higher-quality films with fewer lattice defects than other growth modes. It is likely that the step-flow growth is favored by increasing the misorientation angles, lowering the methane concentrations, and increasing the growth temperatures.