The influence of the magnetron sputtering deposition parameters on opticalproperties of a-C : H thin films

Tetrahedral, highly hydrogenated amorphous carbon films were deposited usin g rf sputtering of graphite by a magnetron sputter source in Ar/CH4 atmosph ere. The optical band gap, Urbach energy and refractive index of the deposi ted films were studied as a function of the bias voltage applied to the sub strate during deposition and gas pressure. The films were characterized by visible spectroscopy, The variation of the optical band gap is considered a s the result of the transition from unsaturated graphitic sp(2) bonds to te trahedral diamond-like sp(3) bonds in the film. The variation of the refrac tive index is correlated with the density and optical band gap of the films .