Critical assessment of thickness-dependent conductivity of thin metal films

Abstract

The possibility of determining transport parameters for the electrical conductivity from its dependence on the film thickness (size effect) is discussed. Measured conductivities are used to assess existing theories on the size effect. Only Namba's model can be fitted to experimental curves and this enables us to determine four parameters, namely the conductivity σ ∞, the mean free path l ∞, the specularity parameter p and the surface roughness h. The experimental curves have to be fitted for very small film thickness to permit a separation of these parameters. The most important thickness range is just that which in the past has usually been excluded from discussion. Careful experiments and careful computer fittings will enable investigations of electronic states in distorted metal films.