Y. Kousar, N. Ali, J. J. Gracio, E. Titus, University of Aveiro, Aveiro, Portugal; M. J. Jackson, W. Ahmed, Purdue University, West Lafayette, IN

Summary: In this paper, we use for the first time, the pulsed-gas time-modulated CVD (PG-TMCVD) process to deposit diamond films onto silicon substrates. This process resembles our earlier proposed TMCVD process, where the key feature of the process was the timed methane (CH4) flow modulations conducted during film growth. In PG-TMCVD, the CH4 is timely pulsed ON/OFF, in a conventional hot-filament CVD system, and this enabled the production of nano-sized and also multi-layered diamond films. We have employed the Taguchi process optimisation technique to optimise the PG-TMCVD process. The results have been compared with those of TMCVD. During the CH4 OFF period, the growing diamond deposits are exposed to hydrogen plasma. This enables the generation of a sharper interface at the diamond film surface layer, which provides the conditions for the production of the new diamond over layer. It was possible to control the thickness of each layer of the multi-layer film system. AFM was used to measure the surface smoothness and the surface morphologies of the deposited films. The diamond carbon-phase purity of the films was characterised using micro-Raman spectroscopy.