INTERPLAY OF QUANTUM-SIZE EFFECT AND SURFACE ELECTRON-SCATTERING IN CONDUCTIVITY OF THIN-FILMS

We constructed the most general theory of the classical and quantum st atic electron transport for 3D films with randomly rough boundaries. T he electron-surface interaction was included via approximation with mi ldly sloping asperities, when the rms height xi of boundary defects is less than their mean length L. Then we analyze influence of spatial q uantization and electron-surface scattering on the film conductivity [ sigma] and their interference. Joint action of those factors leads to peculiarities (sharp dips) of [sigma] versus the sample thickness d ap pearing at points where a new conducting electron channel opens. The d ips have fundamental quantum origin and are caused by size quantizatio n of electron-surface scattering rate. When studying [sigma] versus th e bulk mean free path l of electrons, we revealed than, as bulk collis ions vanish (l --> infinity), the quantum conductivity approaches fini te residual value associated with electron-surface interaction. The re sidual conductivity was first shown to possess either quantum or exclu sively classical origin depending on d, l, and the electron wavelength . On the basis of the investigations provided, the relation between qu antum and classical effects in the film conductivity was clarified. Th e theoretical result were successfully tested against recent experimen tal data concerning the conductivity of ultrathin films.