Study Of The Effects Of Methane Concentration And Off-axis Angle For The Growth Of Single Crystal Diamond

Diamond has excellent properties, such as high hardness and thermalconductivity, thermal expansion coefficient is very small, etc. Now diamond has beenused in the defense to consolidate, industrial production, science and technology, andsome other fields. The preparation of diamond with high quality has attracted theattention of scientific researchers. Especially, achieving high quality single crystaldiamond and high growth rate becomes a pursuit of people.In this paper, single crystal diamonds were grown on HTHP synthetic diamondseeds by MPCVD method. It was found that oxygen has obvious influence on thegrowth of single crystal diamond. The samples were examined by Raman and PLspectrum. The results show that oxygen inhibits the generation of non-diamond phaseand improves the quality of single crystal diamond. However, it will decrease thegrowth rate.We studied the influence of methane concentration on the growth of single crystaldiamond. With the increasing of methane concentration,the growth rate increases. ThePL results show that the methane concentration affects the distribution of nitrogen.When the concentration is low,with the methane concentration increasing, theepitaxial layer becomes thicker and N atoms gradually accumulated resulting in theincreasing of the concentration of nitrogen. However, when the methaneconcentration is10%, the concentration of nitrogen decreased. It may because that thegrowth rate is fast and the nitrogen diffusion velocity is relatively slow. Seen from theSEM and metallographic microscopy, the step densities of the samples are increasingwith the increase of methane concentration when it was lower than10%. Whenmethane concentrations increase to10%, crystal quality improves and the step densityreduces.Off-axis has great influence on the growth of single crystal diamond. Before thegrowth, the diamonds are polished along [100] direction with off-axis angles of0°,1.72°,2.63°, and3.95°. We find that the growth rate of sample with off-axis angle of 3.95°is fastest, and the crystallization quality is best. It shows that theintroduction of off-axis angle improves the growth rate of single crystal diamond.After introducing0.5sccm nitrogen, we found that the growth rate increased when theoff-axis angle is0°. However, the growth rate has no obvious increase when theoff-axis angle is3.89°.