Carbon thin films have been prepared by 248 nm excimer laser vaporization of graphite targets. The effect of a variety of process parameters on the film properties is investigated. Deposition at or below room temperature yields diamond-like films with low hydrogen content, high optical transmission, and high resistivity. Electron energy loss spectra indicate sp3 bond fractions of 70–85%. Detailed analyses of the pseudodielectric functions, measured using spectroscopic ellipsometry, show the films to have normal dispersion and an index of refraction of 2.5 in the visible wavelength region. The effects of a low pressure hydrogen background and the use of auxiliary pulsed and dc plasma enhancements are also examined.
Trends in recently reported data on high sp3 fraction (up to 85%), nonhydrogenated amorphous diamond-like carbon films deposited by ion beam sputtering and laser vaporization are examined. The degree of diamondlike film character is found to depend upon the deposition technique as well as the substrate temperature and thermal diffusivity. The data suggest that the combination of incident particle kinetic energy and surface accommodation determine the physical properties of the resultant film. A model is proposed for the condensation of energetic carbon atoms into diamondlike films in which a quench-type surface accommodation mechanism is operative.
A picosecond pump-probe technique is used to measure the room-temperature thermal conductivity κ and longitudinal sound velocity cl of amorphous diamond (a-D) and diamondlike carbon (DLC) thin films. Both κ and cl were found to decrease with film hydrogen content. Depending on the film deposition technique, κ is in the range 5–10×10−2 W cm−1 K−1 for a-D, and 3–10×10−3 W cm−1 K−1 for DLC. Values of cl were found to be in the range 14–18×105 cm s−1 for a-D, and 6–9×105 cm s−1 for DLC.
Amorphous diamond films have been prepared by filtered cathodic arc deposition of carbon. The filtered arc is well suited for the growth of amorphous diamond, as it provides carbon ions with optimum kinetic energies at practical deposition rates. These films contain no hydrogen and are therefore structurally different from diamond-like carbon films generated by plasma chemical vapor deposition. Diamond-type bonding of carbon is quantitatively determined by electron energy loss spectroscopy, as an sp3 content up to 83% is measured. Data on the macroscopic properties are provided by optical transmittance, ellipsometry, Rutherford backscattering, elastic recoil scattering, and resistivity measurements. The films exhibit high optical transparency and an optical gap of 2.4 eV. Trends in the optical gap and refractive index as a function of deposition energy are consistent with semiconductor theory and indicates a change in the average bond length.
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