Evolution of physical properties of diamond nanoparticles deposited by DC-PECVD method after post deposition annealing

High quality diamond nanoparticles were synthesized by plasma enhanced chemical vapor deposition (PECVD) method on steal 304 substrates. Effects of post deposition annealing in the vacuum at temperature of 100 °C, 200 °C, and 300 °C was studied. Investigations of phase structures and surface morphology of diamond materials were examined by X-ray diffraction (XRD), atomic force microscopy, scanning electron microscopy (SEM) and Raman spectroscopy. The XRD spectrum of the annealed samples showed the well-defined crystalline structure of the diamond nanoparticles with a more intense peak at 100 °C. Post annealing of the samples at higher temperature transforms the diamond structure to graphite phase with is reduced of the film's crystalline quality. A shift in preferred diamond growth orientation at higher annealing temperature from (111) to (220) was happened. Remarkable differences in the morphology were evident in the SEM images of annealed samples. The high concentration and distribution of the diamond nanocrystals with crystallite size of lower than 50 nm were obtained on the surfaces of the annealed sample at 100 °C. Raman spectra showed a more intense diamond peak for annealed sample at 100 °C and graphitic and non-diamond components for annealed sample at higher temperature.