Local transport measurement at mesoscopic length scales on epitaxial graphene using scanning tunneling potentiometry
Abstract/Contents
- Abstract
- Mesoscopic transport is the regime of transport in which quantum interference effects are present. To date there have been no measurements of the local transport potential variation at mesoscopic length scales in macroscopic samples. In this dissertation, we present the first such experimental study. The mesoscopic phenomenon of interest in this study is weak localization in epitaxial graphene. We use scanning tunneling potentiometry (STP) to measure the local transport potential on this material. STP is a scanning-tunneling-microscope-based instrument that is capable of measuring the local transport potential with high accuracy, while obtaining the topography of the sample simultaneously. The spatial resolution under our measurement conditions is of order several nanometers. We will summarize our efforts in developing, understanding and optimizing our STP instrument. Tip jumping artifacts are systematic errors that can occur in STP measurement. It is not possible to completely eliminate such problems if the geometry of the tip is unknown. We limit such problems by using a sharp, slender tip manufactured by focussed ion beam. The practice, benefit, and issues of using such tips in STP experiments are presented. In our data taken at a temperature of 17K, we show that the largest features in the local transport potential are residual resistivity dipoles associated with topographical steps in the sample. On a finer length scale, on the plateau regions of the sample, there are spatially repeatable fluctuations in the measured potential that cannot be understood by simple classical diffusive transport theory. The theoretical understanding of what is measured locally by STP under mesoscopic conditions is not trivial. Lacking a theory on macroscopic samples, we present a heuristic understanding of STP operation to highlight some of the issues one encounters when considering the interpretation of STP results. To understand the effects of quantum interference, the density matrix of the sample is needed. The theory for a macroscopic sample also requires a local description of the density matrix. Such a complete theory requires further development and calculations.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2013 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Wang, Weigang |
|---|---|
| Associated with | Stanford University, Department of Applied Physics. |
| Primary advisor | Beasley, Malcolm |
| Primary advisor | Moler, Kathryn A |
| Thesis advisor | Beasley, Malcolm |
| Thesis advisor | Moler, Kathryn A |
| Thesis advisor | Goldhaber-Gordon, David, 1972- |
| Advisor | Goldhaber-Gordon, David, 1972- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Weigang Wang. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2013. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2013 by Weigang Wang
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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