Structure of a diamond deposited from microwave plasma by a new gas-jet method

Diamond coatings on a molybdenum substrate were obtained by gas-phase deposition from a high-speed jet of activated gases. In the most common case, diamond film is formed as a result of the appearance of discrete nuclei on the substrate, their growing and competing. We observed the formation of coatings consisting of separate isometric aggregates with different types of packaging (111) or (100) plates depending on the process parameters (gas flow, the H2/CH4 ratio, the substrate temperature). The study of coating morphology using optical and electron scanning microscopy suggests that the particles were in the gas phase for a long time and increased to the size of tens of microns, and then deposited on the substrate. This process can be explained by the charged state of the particles, according to the charged cluster model of Hwang (1996). The study of the structure and phase composition by XRD and Raman spectroscopy revealed amorphous carbon, disordered and crystalline graphite, molybdenum carbide with the dominant contribution of diamond). The broadband luminescence of the coating under UV excitation is related to amorphous carbon, whereas 532 nm excitation causes the glow of vacancy centers such as (NV−) and (SiV−). [Display omitted] •Diamond CVD coatings on a Mo substrate were obtained using a high-speed H2/CH4 jet.•Morphology of diamond grains: octahedrons, mesocrystals and aggregates of {100} pieces.•Diamonds are formed and grow to the size of tens of microns in the gas phase.•XRD and Raman study revealed also amorphous carbon, graphite, Mo and Mo carbide.•PL at UV and 532 nm excitations is due to amorphous carbon and vacancy complexes.