Optical absorption and disorder in an amorphous metal

The optical gap Eg of amorphous indium oxide films is measured as a function of static disorder characterized by the dimensionless conductivity g. In the range 1g0.1 the optical gap obeys a scaling relation: ΔEg=-E*Δg where E* is of the order of the Fermi energy of the given sample. These results are ascribed to the continuous shift of the mobility edge in the conduction band with disorder.