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Optical and photoemission studies of DLC films prepared with a systematic variation of the sp3: sp2 composition

: Lifshitz, Y.; Lempert, G.D.; Grossman, E.; Scheibe, H.J.; Völlmar, S.; Schultrich, B.; Breskin, A.; Chechik, R.; Shefer, E.; Bacon, D.; Kalish, R.; Hoffman, A.


Diamond and Related Materials 6 (1997), pp.687-693
ISSN: 0925-9635
Journal Article
Fraunhofer IWS ()
Kohlenstoff-Schichten; spektroskopische Oberflächencharakterisierung; Elektrizität; Magnetismus; Biokompatibilität; Wärmetransport; Keramik

The optical and photoemission properties of hydrogen-free DLC films prepared under conditions which result in different types of carbon bonding (previously determined from electron energy loss spectroscopy) are reported. The films were prepared using a mass selected ion beam deposition system covering the C+ energy range 10 eV - 2 keV, mostly on Si held at room temperature. Previous measurements have shown that the sp3 content of these films varied from 0 to > 80 per cent. The optical constants (n, k absorption coefficient (a)) of theses films were measured by ellipsometry. The energy gaps were derived from Tauc plots (Eg) and from alpha = 10(exp4) cm(exp-1) values (E(0.4)). The enrgy gaps were found to vary with the sp3 content from E < 1 eV (10 per cent sp3) up to E = 2,4 eV (85 per cent sp3). The photoemission absolute quantum efficiencies of these films were independently measured in the UV region using a monochromator system and were compared to those of CVD diamond films and grap hite.