Interrelation of resistivity and inelastic electron-phonon scattering rate in impure NbC films

Abstract

A complex study of the electron-phonon interaction in thin NbC films with electron mean free path $l=2--13\mathrm{nm}$ gives strong evidence that electron scattering is significantly modified due to the interference between electron-phonon and elastic electron scattering from impurities. The interference ${T}^{2}$ term, which is proportional to the residual resistivity, dominates over the Bloch-Gr\"uneisen contribution to resistivity at low temperatures up to 60 K. The electron energy relaxation rate is directly measured via the relaxation of hot electrons heated by modulated electromagnetic radiation. In the temperature range 1.5--10 K the relaxation rate shows a weak dependence on the electron mean free path and strong temperature dependence $\ensuremath{\sim}{T}^{n},$ with the exponent $n=2.5--3.$ This behavior is explained well by the theory of the electron-phonon-impurity interference taking into account the electron coupling with transverse phonons determined from the resistivity data.