Nano-diamond films deposited by direct current glow discharge assisted chemical vapor deposition

Continuous carbon films are deposited by the direct current (DC) glow discharge assisted chemical vapor deposition method using a hydrogen-methane gas mixture. As a result of the DC-glow discharge-surface interaction, the substrate is covered by a film whose properties are strongly affected by the glow discharge and substrate conditions. It was found that under appropriate combination of the experimental parameters, a nano-sized carbon composite film containing a predominating diamond phase can be produced. The properties of the deposited carbon films were studied as a function of experimental conditions by a number of complementary techniques. The composition of the films was assessed by electron spectroscopy and the elastic recoil detection method: the morphology and structure of the films were investigated by high-resolution scanning and transmission electron microscopy (HR TEM and HR SEM). Particular attention was paid to the studies of chemical bonding of the deposited materials. For this purpose, the near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy and electron energy loss spectroscopy (EELS) techniques were used. The average film density was measured by Rutherford backscattering spectrometry. Electron diffraction, NEXAFS and EELS measurements render unambiguous evidence of diamond phase formation by the DC-glow discharge process. The nano-size dimensions of the deposited material were determined from both HR-SEM and -TEM measurements. The critical role of substrate temperature for the formation of nano-diamond particles was established based on the spectroscopic and microscopic results. Hydrogen adsorption/desorption appears to be a critical factor in this process. (C) 2000 Elsevier Science S.A. All rights reserved.