Ultrathick, low-stress nanostructured diamond films -: art. no. 221914

We describe a hot-filament chemical vapor deposition process for growing freestanding nanostructured diamond films, similar to 80 mu m thick, with residual tensile stress levels less than or similar to 90 MPa. We characterize the film microstructure, mechanical properties, chemical bond distribution, and elemental composition. Results show that our films are nanostructured with columnar grain diameters of less than or similar to 150 nm and a highly variable grain length along the growth direction of similar to 50-1500 nm. These films have a rms surface roughness of less than or similar to 200 nm for a 300x400 mu m(2) scan, which is about one order of magnitude lower than the roughness of typical microcrystalline diamond films of comparable thickness. Soft x-ray absorption near-edge structure (XANES) spectroscopy indicates a large percentage of sp(3) bonding in the films, consistent with a high hardness of 66 GPa. Nanoindentation and XANES results are also consistent with a high phase and elemental purity of the films, directly measured by x-ray and electron diffraction, Rutherford backscattering spectrometry, and elastic recoil detection analysis. Cross-sectional transmission electron microscopy reveals a large density of planar defects within the grains, suggesting a high rate of secondary nucleation during film growth. These films represent a new class of smooth, ultrathick nanostructured diamond. (c) 2005 American Institute of Physics.