Simultaneous formation of nanocrystalline and <100> textured and {111} facet dominated microcrystalline diamond films using CH4/H2/O2 plasma

Here, we report on the simultaneous production of a white transparent and a gray translucent microcrystalline diamond film from one microwave plasma chemical vapor deposition (CVD) run and focus on the diamond film morphology on the lower substrate that consisted of a small square Si on a 2-inch Si wafer. The growth was performed with a 0.38% O2 addition into 4% CH4/H2 gas mixture under microwave power 3200 W. Besides the {111} facet dominant morphology, a local gradient morphology is also formed on the lower 2-inch Si wafer in a narrow region surrounding where the upper small square Si was placed. It consists of a narrow gradual morphology transition from nanocrystalline diamond grains through {100} facetted gradually towards a {111} facet dominated feature. In particular, the shining narrow square belt on the centre of 2-inch Si wafer is composed by smooth {100} facets. Based on the relationship between the growth conditions and the diamond film morphologies, we can analyze the impact of the presence of the upper small square Si substrate on the formation of {100} faceted diamond and the uniformity of diamond growth on the lower 2-inch Si wafer. By comparing the present results with our previous experimental work on nitrogen addition, we can deduce that the effect of oxygen addition on diamond growth is not very sensitive to temperature variation and opposite to the role of nitrogen addition. These results can serve as experimental validation for the simulation of the plasma distribution under high power conditions.