TrueOne Semiconductor (China)

Abstract Understanding how hydrogen plasma etches various potential products during the diamond growth process can contribute to improving the knowledge of diamond growth. However, due to the absence of an in situ characterization technique during the etching process, the complex chemical reactions involved in the process obscure the atomic‐scale etching mechanisms. In this paper, the etching mechanisms of diamond (001), graphite (0001), and amorphous carbon substrates irradiated by hydrogen plasmas are investigated and compared using molecular dynamics simulations based on ReaxFF. When the incident energy of H atoms is 1 eV, the rate of carbon loss from graphite and amorphous carbon are far higher than that from diamond. As the incident energy of H atoms increases, the etching rate of diamond shows a slow increase, while the etching rates of amorphous carbon and graphite exhibit more significant increases. It can be concluded that the etching rate of diamond is significantly lower than that of graphite and amorphous carbon under H plasma. In the Chemical Vapor Deposition (CVD) process of diamond growth, the generated graphite and amorphous carbon are rapidly etched, leaving only diamond. This offers a plausible explanation for the growth mechanism of diamond through CVD.

The study of the distance between the substrate edge and the substrate holder cavity edge on the growth quality was further carried out. The results showed that the substrate edge quality decreased with the increase in the distance from the substrate edge to the substrate holder cavity edge, and the lateral growth rate significantly increased. Therefore, a three-step growth method was proposed. After 68 h of growth, the substrate size grew from 3.57 mm × 3.63 mm × 1.01 mm to 6.13 mm × 6.04 mm × 2.52 mm, but at the end of the third step, the quality and the morphology of the substrate became poor. Two experiments were carried out to verify the influence of eccentric placement and the substrate holder cavity edge on the substrate morphology. The results showed that the influence of the substrate holder cavity edge on the substrate edge quality was more significant than that of eccentric placement. Because of the lateral growth, the substrate edge will inevitably be closer to the cavity edge during the growth, and its temperature gradient will increase. Therefore, an improved substrate holder was designed, and the simulation results showed that the new substrate holder could effectively guarantee the uniformity of the temperature gradient on the large-scale substrate surface.

ABSTRACTLarge-scale molecular dynamics vapour deposition simulations have been performed to study the homoepitaxial growth of AlN films on non-polar (11-20) AlN surfaces. The effect of growth temperature and injected N: Al flux ratio on the crystallinity and surface morphology of deposited AlN film are investigated. We find that as the growth temperature increases from 1000 K to 3000 K at injected N:Al flux ratio of 2.0, the crystallinity and surface morphology of deposited AlN film both reach the optimum at 3000 K. Increasing the growth temperature makes the adatoms more mobile to move to their ideal lattice sites. Thus, the amorphousness and defects can be effectively reduced and good crystallinity and surface morphology could be obtained. Moreover, when the N:Al flux ratio increases from 1.2 to 2.4 under the growth temperature of 2600 K, the crystallinity and surface morphology of deposited AlN film both reach the optimum at injected N: Al flux ratio of 1.6. The improved crystallinity and surface morphology can be reached by using the optimised N: Al flux ratio. Furthermore, our simulation deepens the understanding and provides guidance for the growth of AlN on the non-polar (11-20) surface in the future.