Study of polycrystalline diamond deposition by continuous and pulsed discharges

The effects of pulsed microwave discharges on the deposition and properties of a set of polycrystalline diamond films are investigated by varying the duty cycle at a fixed pulse frequency and keeping constant the peak microwave power at 1250 W, the substrate temperature and the final film thickness. The deposition of polycrystalline diamond films obtained from highly diluted CH4 (1% CH4 in H2) gas mixtures was monitored by pyrometric interferometry technique. This analysis evidences that, in order to obtain the same thickness, the nucleation/deposition times and the process rates increase and decrease, respectively, by decreasing the pulse duration. Moreover, the influence of the variations of duty cycle on the deposition rates, the surface morphology, the optical properties (refractive index and extinction coefficient) and the crystallite orientations of the polycrystalline diamond films is investigated.