以掃描穿隧式顯微術針對奈米自行組織表面結構之研究

Abstract

Two kinds of self-organized surface nanostructures are investigated with scanning tunneling microscopy in the experiments reported in this thesis.

The first experiment was performed at low temperature (ranging 55K~ 140K) to explore the growth behavior of atomic flat Pb films on incommensurate Pb/Si (111)-1×1 substrate. This is the first systematic investigation of this system at such a low temperature. While the growth of Pb film showed typical features of quantum size effect, certain growth behaviors different from its counterparts at higher temperature, such as the layer-by-layer mode of growth, was observed. The low temperature environment also enabled us to focus on the quantum size effect, which is hindered in the higher temperature regime. In the second part of the thesis, the possibility of selective faceting on Mo (111) surface is explored through series of experiments accounted in this chapter. Facet is considered to be a self-assembled surface nanostructure, whose formation is due to the minimization of surface energy. Inspired by previous experience that carbon contaminated Mo (111) substrate is incapable of faceting, we deposited ethylene (C2H4) on Mo (111) surface to form stable Molybdenum carbide that is only a few atomic layers thick and capable of blocking facet formation on the substrate. An ion beam collimator made of anodic porous alumina was fabricated and tested for guiding the ion bombardment to make recognizable pattern of faceting/non-faceting interface on the sample. We expect to see facets occur only at the area that is sputtered if this is achieved. Preliminary attempts and achievements are reported in this part of the thesis, which showed some positive signs of the scheme that we have proposed.