Scanning Tunneling Microscopy and Spectroscopy of Defects in Low-Dimensional Materials
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Date
2022-02-18
Authors
Mills, Jon
Journal Title
Journal ISSN
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Publisher
University of Oregon
Abstract
With semiconductor device dimensions shrinking to smaller and smaller sizes the individual components become more susceptible to surface or interface atomic defects, as the surface atoms are a larger percentage of the whole device, the interface electronic structure quickly becomes the electronic structure of the whole device. Here we use scanning tunneling microscopy and scanning tunneling spectroscopy (STM/STS) along with density functional theory (DFT) calculations to investigate the impact of the atomic scale defects on the local density of states (LDOS) of a variety of low-dimensional materials. First, we will show work investigating defects in hydrogen-passivated silicon nanocrystals deposited on the Au(111) surface. Using two-dimensional STS spatial mapping we will show both localized and delocalized defect induced states in the LDOS. We will show how surface reconstruction or single-atom defects account for the changes in the LDOS. Then we will report on an exotic two-dimensional structure, an alkali halide ultra-thin film with trigonal planar coordination. Using a combination of STM and DFT we will show, for the first time, how a submonolayer of rubidium iodide coordinates to the Ag(111) substrate, and how upon increasing monolayer coverage the RbI film will reconstruct into the traditional (100) terminated structure. We will end with a study of the impact of defects in an ultra-thin film dielectric on the electronic structure of single walled carbon nanotubes. The research presented in this dissertation increases our understanding of how atomic defects impact the electronic structure of low-dimensional materials, This dissertation includes both previously published and unpublished co-authored material.
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Keywords
Scanning Tunneling Microscopy, Scanning Tunneling Spectroscopy, Surface science