Macrotexture and growth chemistry in ultrananocrystalline diamond thin films

We have determined the average preferred crystalline orientation of thin ultrananocrystalline diamond (UNCD) films using X-ray diffraction. The grain size and lattice parameters of the films were also calculated. We show how these characteristics change markedly with the gas chemistry used during growth, adding either 0-20% nitrogen or 0-15% hydrogen to the argon-rich, argon and methane microwave plasma used. We discuss how these changes give evidence that there is a competing growth mechanism between C2 dimer mediated growth and the more widely used methyl radical growth process. Finally, we identify an additional X-ray diffraction peak, dependent on both the substrate used and growth conditions, as silicon carbide. We discuss these results in the context of the growth mechanisms of ultrananocrystalline diamond.