PULSED-LASER DEPOSITION OF DIAMOND-LIKE AMORPHOUS-CARBON FILMS FROM GRAPHITE AND POLYCARBONATE TARGETS

Amorphous carbon (a-C) and amorphous hydrogenated carbon (a-C:H) films are produced by 248 nm pulsed laser ablation of graphite and polycarb onate targets in high vacuum conditions. Plasma plumes generated by ta rget irradiation with different laser fluences are investigated with l aser induced fluorescence spectroscopy and an electrostatic probe. Ion s of C2+ With kinetic energies of several hundred eV are detected in t he leading edge of the plasma plumes from both targets. These energeti c species are proposed to be responsible for the formation of film str uctures corresponding to diamond-like carbon (DLC), as it is found fro m electron-energy-loss spectroscopy (EELS) and Raman investigations of 0.5 mu m films deposited onto steel substrates. The validation of a l aser wavelength/fluence region for DLC formation found earlier for gra phite targets is discussed and expanded to polycarbonate targets. An i ncrease in laser fluence leads to higher percentages of sp(3) bonds in the a-C and a-C:H films. For the a-C:H films, the incorporation of la rge molecular conglomerates ejected from polycarbonate targets results in the formation of unique heterogeneous structures revealed from sca nning electron microscopy (SEM) studies. The embedded conglomerates ca use a decrease in the a-C:H film hardness to 15 GPa, in comparison to 60 GPa for the a-C films. (C) 1995 American Institute of Physics.