Relationship between sp(2) carbon content and E-04 optical gap in amorphous carbon-based materials

A decreasing trend of the optical gap E-04 with increasing sp(2) carbon con tent has been noticed in amorphous carbon thin films. This behavior is comm on to materials grown using different deposition methods and having differe nt composition and local structure. The use of a model of density of states in which the pi bands are assumed to be Gaussian shaped allows us to expla in such behavior, once the role of network distortion and hydrogen content in determining the width of the bands is taken into account. (C) 1999 Ameri can Institute of Physics. [S0003-6951(99)01149-3].