Optical and photoemission studies of DLC films prepared with a systematic variation of the sp(3):sp(2) composition

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 sp(3) content of these films varied from 0 to >80%. The optical constants (n, k, absorption coefficient (alpha)) of these films were measured by ellipsometry. The energy gaps were derived from Tauc plots (E-g) and from alpha = 10(4) cm(-1) values (E-04). The energy gaps were found to vary with the sp(3) content from E < 1 eV (10% sp(3)) up to E = 2.4 eV (85% sp(3)). 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 graphite. (C) 1997 Elsevier Science S.A.