DIAMOND GROWTH FROM A MIXTURE OF FLUOROCARBON AND HYDROGEN IN A MICROWAVE PLASMA

The process of diamond deposition on Si(100) substrates is examined in a microwave plasma using tetrafluoromethane (CF4) and trifluoromethane (CHF3) as well as methane (CH4) as the carbon source. Substrate pretreatment with diamond powder is effective for the enhancement of diamond nucleation for all the reactant systems tested. Well-faceted diamond of high quality is formed at a gaseous carbon concentration of about 1%. For CF4 H-2 and CHF3-H-2 systems the growth rate of diamond is nearly constant at temperatures above 850-degrees-C, while in the temperature range from 640 to 850-degrees-C it decreases not only with decreasing deposition temperature but also with increasing fluorine content of the reactant. The apparent activation energy for diamond growth is estimated as 119 kJ mol-1, 86 kJ mol-1 and 43 kJ mol-1 for the CF4-H-2, CHF3-H-3 and CH4-H-2 systems respectively. The growth behaviour in the fluorocarbon gas systems differs from that in the CH4-H-2 system. Fluorine compounds seem to terminate active sites of the growing diamond at temperatures lower than 850-degrees-C and to remove non-diamond phases above 850-degrees-C.