“Diamond-like” 3-fold coordinated amorphous carbon

Abstract

Evaporated and sputtered a-C films deposited at L.N. temperature were prepared and studied as a function of annealing using Raman, electron energy loss, and ESR techniques. The reduced Raman spectra of virgin films reflect the one phonon density of states of graphite. Moreover, no evidence for diamond bonding is found from the electron energy loss experiment. Upon annealing, graphitic structural correlations develop within bounded islands of carbon atoms. This picture is consistent with ESR measurements which yield 3 × 10¹⁹ spins/cm³ independent of annealing but a resonnance line (g = 2.002 ± .0005) that narrows with annealing. A model based solely on a three-fold coordinated random network structure will be presented to explain the “diamond-like” physical properties of a-C films and their changes with annealing.