| Summary: | Semiconductor nanostructures formed by a surface modification process caused by ion sputtering is studied in this thesis. The microscopic dynamics of the semiconductor surface undergoing ion impingement is discussed in detail. Due to the promising controllability and minimal damage creation on the substrate, low ion energy Ar+ sputtering is adopted in the investigation. GaAs, because of its proven importance in the fundamental quantum effect studies, is selected to be the semiconductor platform on which extensive experimental activities are carried on. The Ar+ sputtering induced GaAs(100) surface morphology evolution below 1200 eV ion energy is firstly investigated. The sputtered surface is examined and characterized by atomic force microscopy (AFM). It has been found that no regular surface patterns can be observed when the ion energy is in the low eV range. Nanograins mixed with irregularities start to develop and grow with increasing ion energy above the mid eV energy range, and regular QDs can be obtained typically at ion energies near 1000 eV. The energy dependent dot evolution is evaluated based on solutions of the isotropic Kuramoto-Sivashinsky (KS) equation. The result suggests that ion energy is one dominant factor that influences the QD formation process when the semiconductor surface is sputtered at low ion energy. Our study has proved the feasibility to fabricate GaAs QDs using low energy ion sputtering, and this fabrication process can be well controlled by the energy dependent QD formation model.
|
|---|