Electron transport properties of amorphous Cu-Ag films

Abstract

Amorphous films of Cu_0.5Ag_0.5 are prepared by vapour-quenching of the alloy onto glass substrates held at 80 K. Resistivity, Hall coefficient, thermoelectric power, their temperature dependence, and annealing kinetics are studied in-situ in the temperature range 80 to 300 K. As-deposited films exhibit high resistivity (≈100 μΩ cm), and thermopower (≈+40 μV/K), and a small mobility (≈0.5 cm²/Vs). On annealing above 80 K, the resistivity and thermopower of the films show rapid decrease in two steps starting at ≈120 and ≈240 K. The Hall coefficient changes slightly only during the second step. The transport properties and their annealing kinetics depend critically on the deposition parameters of films. The temperature coefficient of resistivity is negligibly small up to 160 K, above which it increases gradually to reach a small positive value of 1.8 × 10^-3 at 300 K. The thermopower of amorphous as well as crystallised films is independent of temperature. The observed behaviour of transport properties can be qualitatively understood in terms of enhanced scattering of conduction electrons by quenched-in extended defects, or alternatively, in terms of liquid-like scattering with a suitably chosen pseudopotential.