Nanocrystalline diamond films: Growth and gas phase modeling studies in inert gases

It is highly desirable for biomedical and nanotechnology applications to be able to deposit smooth adherent diamond films on a variety of substrate materials. The properties of these films are however affected profoundly by the process parameters such as deposition temperature, gas composition, pressure, etc. In this study, we present an insight into the gas phase chemistry involved in the chemical vapor deposition of smooth nanocrystalline diamond films using Ar/CH4/H2 and He/CH4/H2 precursor mixtures. Experimental results on the growth, surface morphology and crystalline structure are presented. It is evident that the addition of a noble gas such as argon has a considerable effect on the gas surface chemistry. At low Ar concentrations standard polycrystalline diamond is produced. However, at high concentrations of inert gas dilution (>90 vol % Ar) there are significant changes in the diamond crystallinity ranging from sub micron to nanocrystalline facets at Ar concentrations > 98 vol. %. Modelling of the gas phase chemistry using the CHEMKIN modelling package show that the relative concentrations of the important diamond growth species CH3 and C2H (and by implication C2) prevailing during the deposition process alter significantly as a function of Ar concentration. This, in turn, affects surface morphology and crystallinity of the deposited films. Copyright © 2006 ASM International®.