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 pr epared under conditions which result in different types of carbon bond ing (previously determined from electron energy loss spectroscopy) are reported. The films were prepared using a mass selected ion beam depo sition system covering the C+ energy range 10 eV-2 keV, mostly on Si h eld 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 b y 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 t o 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 the se films were independently measured in the UV region using a monochro mator system and were compared to those of CVD diamond films and graph ite. (C) 1997 Elsevier Science S.A.