Quantum Electronic Effects on the Properties and Growth of Thin Films and Nanostructures

T. -C. Chiang

《Chinese Journal of Physics》 43卷1S期 (2005/02) Pp. 154-168

並列摘要

The electronic structure of a thin film is modified relative to the bulk by the presence of the film's boundaries. In systems with well-ordered interfaces, the component of the electronic wave vector perpendicular to the film becomes quantized due to confinement, and the continuum of states characteristic of the bulk is replaced by a discrete set of quantum well states or subbands. This quantization leads to changes in electronic structure, and the physical properties can be very sensitive to the system dimensions and boundary conditions. This article reviews recent investigations of such quantum size effects in atomically uniform metallic films of Ag on Fe(100) and Pb on Si(111). Atomic-layer-by-atomic-layer variations in properties, including thermal stability, work function, electron phonon coupling, surface energy, and internal structural distortion are measured by photoemission and x-ray diffraction. The results are correlated with the measured changes in electronic structure, and are compared with simple model predictions and first-principles calculations. Issues related to morphological evolution during growth and annealing are also examined and explained in terms of a surface energy function which can be determined directly from an analysis of the film thickness distribution of a thermally roughened film.