Extended and Localized Electronic States in Tetrahedral Carbon Films

The disordered tetrahedral carbon films have been grown by ion beam deposition at ∼120 eV. An absorption maximum 6.15-5.80 eV (E 0 B ) and a threshold 4.8-4.5 eV were resolved and tentatively attributed to Γ 5 + - Γ 5 - and Γ 5 + - K2 transitions in lonsdaleite. The cubic sp3-carbon manifested as maxima at 5.45-5.50 eV (Γ′25 - Δx) and 7.0 eV (Γ′25 - Γ15). Urbach tails of different steepness were resolved. A 6.508 eV maximum of 0.52 eV half-width at 90K was resolved. The spectroscopic data on absorpsion and luminescence of sp3-bonded carbon films of different allotropies are discussed.