Growth of carbon with vertically aligned nanoscale flake structure in capacitively coupled rf glow discharge

Carbon nanoflakes (CNFs) have been deposited on Si (10 0) wafer substrates at a substrate temperature of 670 degrees C from a glassy carbon target by capacitively coupled rf (13.56 MHz) glow discharge using a mixture discharge gas of Ar and CH4 with a total pressure of 14.5 Pa. Microstructures of deposited carbon were investigated by a field emission scanning electron microscope (FESEM) and a high-resolution transmission electron microscope (HRTEM). Under the given conditions, vertically aligned CNFs with a flake length of about 1 mu m and thickness of about 20nm were grown. High intensity and symmetry of electron diffraction pattern indicate that the CNFs deposited by capacitively coupled rf glow discharge have three-dimensionally perfect crystallinity with a graphene interlayer spacing of 335 pm. In particular, there is little disorder in stacking of the layer structure. It was further found that the thickness of the flakes was less dependent of deposition time while the length of the flakes increases to about 1 mu m with increasing deposition time to 3 h. The growth rate of a graphite sheet parallel to (0 0 1) stacking layers was much higher than that perpendicular to (0 0 1) stacking layer, resulting in anisotropic growth of a flake-like structure. The formation mechanisms of CNFs are discussed from the viewpoint of the difference in residence time of carbon atoms on CNF surfaces parallel to and perpendicular to (0 0 1) direction and anisotriopic heat conductivity of graphite. (C) 2007 Elsevier Ltd. All rights reserved.