Electrical conductivity and thin-film growth dynamics

Abstract

It is known that surface steps can give rise to diffusion barriers and generate moundlike rough surfaces during thin-film growth. We study the influence of moundlike rough surfaces on electron scattering and electrical conductivity of semiconducting and metallic thin films. For a semiconducting film, the intraminiband cutoff ${q}_{c}$ limits the contribution from mound surface scattering. Three different cases are illustrated to show how surface morphology affects the conductivity: ${q}_{0}<{q}_{c},$ ${q}_{0}{=q}_{c},$ and ${q}_{0}>{q}_{c}.$ Here ${q}_{0}$ is the ring position of the surface power spectrum. For a metallic film with a single rough boundary, quantum size effect (QSE) oscillations are shifted in phase and weakened by the presence of wavelength selection in surface morphology. In this case, the conductivity reaches a minimum at a certain value of the system correlation length \ensuremath{\zeta} when the mound separation \ensuremath{\lambda} obeys the condition $\ensuremath{\lambda}>{\ensuremath{\lambda}}_{F}$ or $\ensuremath{\lambda}<{\ensuremath{\lambda}}_{F}$ $({\ensuremath{\lambda}}_{F}$ being the Fermi wavelength). The presence of cross correlation in films with two rough boundaries greatly influences the initial stage of QSE oscillation of metallic films. Finally, we show that the size and shape of quantum effects depend very much on the different growth modes. The power-law behavior of the conductivity versus film thickness can be dramatically altered during dynamic growth, which provides a reasonable explanation for recent experiments.