Nanometer scale patterning on silicon(100) surfaces by an AFM.

摘要

This dissertation discusses the generation of nanometer scale patterns on silicon substrates by an atomic force microscope (AFM). It covers the characterization of the nano-patterns as well as the mechanisms involved in the pattern formation process. Further, techniques for the transfer of the patterns onto the silicon substrates will be presented.; In the pattern generation process, the AFM tip was biased at a negative voltage to cause local chemical reactions in the surface atoms. Nanometer scale patterns have been demonstrated on both Si surfaces and Cr films. The process is reliable and reproducible under a well controlled ambient. The inspection of the surface modifications was also done by the AFM. Features as small as 10 nm have been achieved.; The chemical properties were analyzed by both chemical etching in different solutions and Auger electron spectroscopy. Strong evidence shows that the produced materials are oxides, SiO{dollar}sb2{dollar} for the Si surfaces and CrO{dollar}sb{lcub}x{rcub}{dollar} for the Cr films. The dependences of the AFM writing process on the tip bias, the writing time, and the ambient were investigated. Based on these investigations, the writing mechanism is attributed to local oxidation of surface atoms induced by the high electric field, which is enhanced with the presence of water vapor.; Pattern transfer was carried out by reactive ion etching (RIE) and by wet etching. The SiO{dollar}sb2{dollar} patterns were found to be effective masks in a wet etching process as well as in a RIE process. On the other hand, by selective wet etching, the patterns generated on the Cr films were transferred onto thermal oxide films (grown on Si substrates), which can then be used as masks in subsequent pattern transfer processes.; Finally, appended to this dissertation is additional work on the study of Schottky barrier heights for epitaxial CoGa films grown on n-type (100) GaAs by ballistic-electron-emission microscopy. Both (100) and (110) oriented CoGa films were studied. This work gives a microscopic view of the interfacial barriers for these films. In addition, it provides insights into the electron transport properties across the interfaces.