Studies of nanoscale structure and its transformation in pulsed-laser deposited dense diamond-like carbon films

Dense diamond-like carbon (DLC) thin films were deposited at room and liquid nitrogen temperatures on Si and SiO2 substrates by pulsed-laser sputtering of a graphite target in a high-vacuum (similar to 10(-6) Torr) chamber. The high density (similar to 3.05 g/cm(3)) of the films was evaluated by comparison of the intensity of carbon core electron excitation energy peaks in X-ray photoelectron spectra (XPS), measured for diamond, graphite and DLC films. Direct experimental evidence is presented for the first time that DLC films deposited at room temperature are essentially amorphous. Graphite nanocluster formation is observed as the appearance of a graphitic nanocluster system suspended in a dense sp(3) amorphous matrix. Data obtained by Raman spectroscopy, IR vibrational spectroscopy, XPS, electron energy-loss spectroscopy (EELS) and transmission electron microscopy (TEM) show that the transformation of the amorphous mixture of sp(3) and sp(2) bonded carbon atoms into the graphitic nanocluster system occurs as a result of the ordering of the sp(2) bonded carbon atoms in the process of annealing at temperatures which are only about two times higher than the temperature of deposition. (C) 1997 Elsevier Science S.A.