Epitaxial Nanotemplates for Strain Modulated Carrier Confinement in Silicon

Abstract

The fundamental goal of this thesis is to characterize and assess the effects of strain, chemistry, and growth orientation on the structure of complex epitaxial heterostructures. In this dissertation, we discuss artificial patterning, formation, and encapsulation of Ge quantum dots (QDs). Precise spatial ordering of QDs may enable predictable quantum states due to direct exchange interactions of confined carriers. The realization of anticipated quantum states may lead to unique functionalities such as cluster qubits and spintronic bandgap systems. In order to define exemplary quantum architectures, one must develop control over QD size and spatial arrangement on the sub-35 nm length scale. We employ fineprobe electron-beam irradiation to locally decompose ambient hydrocarbons onto a bare Si (001) surface. These carbonaceous patterns are annealed in UHV, forming ordered arrays of nanoscale SiC precipitates that may template subsequent epitaxial Ge and Si growth to form ordered hybrid Ge/SiC or Si/SiC QD arrays on ultra-small length scales. First, we investigate the templated feature evolution during UHV annealing and subsequent Ge epitaxial overgrowth to identify key mechanisms that must be controlled in order to preserve pattern fidelity and reduce broadening of the nanodot size distribution. We find that to obtain the narrow size distribution required for spintronic applications, one must precisely control the total thermal budget. Next, we show that sub-10 nm 3C-SiC nanodots form, in cube-on-cube epitaxial registry with the Si substrate. The SiC nanodots are fully relaxed by misfit dislocations,

Synthesis and Characterization of Nano-to Meso Scale Ordered Structures in the Si1-xGex Alloy System

“…The mechanical process of TEM sample preparation has been well described and documented by our group in the past. 68,69 For FIB lift-out process, the scanning electron microscopy (SEM) images…”

Self-Assembled Epitaxial Multiferroic Oxide Nanostructures Grown by Pulsed Electron Deposition

“…The NT-MDT system was used for initial magnetic force microscopy measurements prior to the purchase of the Cypher system and has been described elsewhere. 140 The Asylum Research Cypher scanning probe microscope is designed to permit easy operation of a variety of scanning probe techniques. A photograph of the entire system is shown in Figure 4-6.…”