Evolution and properties of nanodiamond films deposited by direct current glow discharge

Nanocrystalline carbon films possessing a prevailing diamond character are deposited by a direct current glow discharge chemical vapor deposition meth od using a 9:91 vol % methane to hydrogen gas mixture. In the present work the evolution and properties of nanodiamond films deposited by this method onto silicon substrates as a function of time were studied by various compl ementary techniques. Our analysis showed that prior to formation and growth of continuous films of a predominantly nanodiamond character, a graphitic phase is formed. After the nanodiamond phase is stabilized, near edge x-ray adsorption fine structure measurements proved the predominant diamond char acter of the film to be about 80%. By electron energy loss spectroscopy ana lysis the sp(2)-like character of the nanodiamond grain boundaries has been determined. The nanodiamond films were found to be thermally stable up to temperatures of similar to 950 degreesC as established by vacuum heating. B y scanning electron microscopy and atomic force microscopy the morphology o f the films was examined showing that the formation of the nanodiamond phas e is initially accompanied with an increase in surface roughness which decr eases with film growth. By high-resolution transmission electron microscopy it was determined that the continous nanodiamond films are composed of dia mond nanocrystallites, 3-5 nm in diameter. (C) 2001 American Institute of P hysics.