N. Ali, Y. Kousar, J. J. Gracio, Q. H. Fan, University of Aveiro, Aveiro, Portugal; W. Ahmed, University of Ulster, Newtownabbey, United Kingdom; M. J. Jackson, Purdue University, West Lafayette, IN; A. A. Ogwu, University of Paisley, Scotland, United Kingdom
Nanocrystalline diamond films were deposited using the new time-modulated chemical vapour deposition (TMCVD) process. The key feature of TMCVD is that it modulates methane (CH4) flow during diamond CVD, whereas, in conventional CVD, the CH4 flow is kept constant throughout the deposition process. Films grown using TMCVD were smoother, harder and displayed better quality than similar films grown using constant CH4 flow during CVD. The advantage of using TMCVD is that it promotes secondary nucleation to occur onto existing diamond crystals. Pulsing CH4, consecutively, at high and low concentrations allows the depositing film to maintain its quality, in terms of diamond-carbon phase. Films grown under constant CH4 flow during diamond CVD displayed a columnar growth mode, whereas, with the time-modulated films, the growth mode was different.
Summary: TMCVD renders greater control over microstructure. With TMCVD it is possible to control grain size of the resultant diamond film. The key feature of the TMCVD process is that it modulated methane flow during diamond deposition. The time-modulated films are found to display superior properties to the conventional diamond films.
