Fabrication of tubes of diamond with micrometric diameters and their characterization

The fabrication and characterization of 'self-supporting' diamond tubes grown by chemical vapor deposition (CVD) are reported. Diamond layers were deposited onto tungsten wires with diameters of 238 μm; the tungsten cores were subsequently completely removed by etching to leave 'self-supporting' diamond tubes with a diameter of approximately 400 μm and length of 20 mm. A hot-filament CVD system fed with ethanol highly diluted in hydrogen was employed. Growth rates of 7.8 μm h-1 have been measured and incubation times >3 h have been estimated. Scanning electron microscopy of cross-sections revealed columnar structures, which terminate on sharp (111) facets on the tube's external surface. Raman spectroscopy showed that the tube structure is predominantly composed of C-C sp3 bonds, with intrinsic tensile stresses