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Nanocrystalline diamond (NCD) membranes of 150 nm thickness and diameters in the millimeter range grown by microwave-assisted chemical-vapor deposition were bulged to investigate their mechanical properties and their use as tuneable optical lenses. The NCD films were grown at different CH4/H2 gas mixtures to vary the sp2/sp3 ratio and thereby to tune their mechanical, optical, and surface morphology properties. By applying gas over pressure the membrane forms a lens shaped geometry. From deflection data we calculated Young’s moduli which decrease with increasing CH4/H2 ratio from 1160 GPa at 0.5% to 900 GPa at 7%. Optical lens applications show a variation in the focal point from infinity to 3.5 mm. The data indicate that NCD is a promising material for tuneable optical lenses applications. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline diamond films thinner than 140nm are demonstrated to exhibit Young’s moduli as high as single crystal and microcrystalline bulk diamond when grown under appropriate conditions. The Young’s modulus of nanocrystalline diamond is shown to be a function of the methane concentration and the microwave power density when grown by microwave plasma enhanced chemical vapour deposition. The variation of Young’s modulus can be correlated with the sp2 content and crystallite size of the films as characterised by Raman spectroscopy and Scanning Electron Microscopy. [Copyright &y& Elsevier]

Abstract: We report on a general method to fabricate transition metal related defects in diamond. Controlled incorporation of Mo and W in synthetic CVD diamond was achieved by adding volatile metal precursors to the diamond chemical vapor deposition (CVD) growth process. Effects of deposition temperature, grain structure and precursor exposure on the incorporation efficiency were systematically studied, and doping levels of up to 0.25at.% have been achieved. The metal atoms are uniformly distributed throughout the diamond grains without any indication of inclusion formation. These results are discussed in context of the kinetically controlled growth process of CVD diamond. [Copyright &y& Elsevier]