Realization of different carbon nanostructures by a microwave plasma enhanced chemical vapor deposition technique

Various process conditions are summarized that allows one to grow carbon nanostructures (carbon nanotubes and nanodiamonds) and diamond-like carbon (DLC) films at room temperature by exciting C2H2 + Ar plasma in a microwave plasma enhanced chemical vapor deposition (PECVD) system. These nanostructures are formed at some specific but different parameter space. The films were characterized by atomic force microscopy, cathodoluminescence (CL), Raman spectroscopy, transmission electron microscopy and glancing-angle X-ray diffraction (XRD) techniques. DLC films were deposited with different applications in mind. The films were ultra smooth with RMS roughness <0.07 nm and found to show CL when excited with an electron beam. Carbon nanotubes and nanodiamond structures were obtained simply by varying the applied RF bias at an optimized microwave power of 25 W. Again, the nanodiamond films were found to be ultra smooth (RMS roughness <0.06 nm) with 60-100 nm grain size nanocrystallites. The Raman and glancing angle XRD analysis suggests hexagonal polymorph structure for nanodiamond crystallites. Carbon nanotubes grown on ophthalmic glass substrates at room temperature, without any preconditioning and intentional heating of substrate, were found to be multiwalled with their diameters varying from 23-30 nm at optimized parameters. (C) 2001 Elsevier Science B.V. All rights reserved.