Dependence of the Phase-Coherence Time in Weak Localization on Electronic Mean Free Path and Film Thickness

Abstract

Magneto-resistance measurements on thin disordered films yield the phase-coherence time τ_i of the conduction electrons (weak localization). The dependence of τ_i on film thickness and residual resistivity are reported for disordered Au, Ag and Mg films in the temperature range between 4.5 and 20 K. The resistivity of the films was varied between .13 and 1.1×10⁻⁶ Ωm. The temperature dependence of 1⁄τ_i follows a T^p-law. The exponent is essentially two, but varies slightly with the resistivity. 1⁄τ_j depends much less on the resistivity than the linear prediction of the theory. No direct influence of the film thickness on τ_i was observed. This excludes the impurity induced Coulomb interaction as the relevant mechanism and suggests that τ_i is essentially determined by electron-phonon interaction. However, at the present time there is no theory available that reproduces the experimental results. Measurements of the (temperature independent) Hall-constant suggest that the thin films are rather homogeneous despite their small thickness.