Nanocrystalline diamond thin films synthesis on curved surface

Thin films of curved surface nanocrystalline diamond (CS-NCD) are a category of important materials. However, the development of such materials is still a highly challenging task. Here we present a novel approach to synthesizing CS-NCD thin films deposited on non-spherical surfaces of molybdenum substrate using direct current plasma jet chemical vapor deposition. A special cooling system was designed and applied to ensure uniform substrate temperature. It is demonstrated from simulation and experimental results that this system is favorable for the production of thin films. The results show that the quality of CS-NCD thin films depends on the selection of optimal values of parameters including CH₄ concentration, substrate temperature, and chamber pressure. If the CH₄ concentration and/or the substrate temperature is too high or low, it results in non-diamond phase or micron-crystalline diamond thin films. Synthetic CS-NCD thin films using the proposed method have a smooth surface and uniform thickness. The average grain size and the mean surface roughness are approximately 30 and 4.3 nm respectively. Characteristics of CS-NCD thin film spectra comprised of the full width at half maximum with broad Raman peaks around 1,140 and 1,480 cm^-1, confirming the presence of the NCD phase.