Synthesis of Multilayered Diamond Films in Microwave Plasma with Periodic Nitrogen Injections

Abstract

The use of polycrystalline diamond in optics (transparent windows) and electronics (heat sinks) usually requires polishing of a synthesized wafer. However, mechanical polishing of diamond faces certain difficulties, since it is a material with a record high hardness. In this study, we propose a new approach to forming low-roughness diamond layers by periodic time-limited adding (injection) of nitrogen into the standard methane‒hydrogen (CH₄–H₂) gas mixture. Nitrogen stimulates secondary nucleation on the formed well-faceted micrometer diamond grains, which prevents their further growth. The transition from a continuous supply of N₂ to short-term injections prevents the formation of continuous nanocrystalline diamond layers and makes it possible to grow high-quality microcrystalline diamond layers between the nitrogen injection periods.