Hybrid ionic liquid - boron nitride gates for clean, high carrier density transistors
Abstract/Contents
- Abstract
- Using gates to change carrier density via the electric field effect is a cornerstone of condensed matter physics. Gating using ionic liquid electrolytes has recently generated considerable interest as a method to achieve large carrier density modulations in a variety of materials, opening routes to devices based on physics accessible only at carrier densities beyond the breakdown limit for oxide dielectrics. However, electrolyte gates can chemically modify the channel due to electrochemically driven reactions and increase carrier scattering due to the proximity of the ions in the electrolyte to the carriers in the channel. In this work, I discuss how inserting a thin layer of hexagonal boron nitride between the electrolyte and the channel prevents chemical modification and suppresses scattering, while still allowing carrier densities significantly beyond those possible with oxide dielectrics. I begin with a brief introduction to electrolyte gating using ionic liquids, including the use of reference electrodes in three terminal measurements. In the second chapter, using a combination of in situ x-ray spectroscopy and electrochemical techniques, I show that trace impurities in the ionic liquids can cause reversible electrochemical oxidation of a gold channel and that a thin boron nitride layer prevents this oxidation. I then take a brief digression to discuss how x-ray scattering can be used to learn about surface and interface structure. I develop a new model for analyzing crystal truncation rods from miscut surfaces that can be used to learn about terrace morphology and that has a simple roughness factor to account for disorder from terrace steps in the truncation rod intensity. In the fourth chapter, I use x-ray reflectivity to probe the spatial arrangement of the ions on a strontium titanate channel, and show that the timescale for ion rearrangement matches the timescale for the onset of electrical conduction, suggesting an electrostatic gating effect. Finally, I show that boron nitride spacers significantly improve carrier mobility in graphene channels and that the remaining scattering arises primarily from ions in the bulk liquid.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2017 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Petach, Trevor | |
|---|---|---|
| Associated with | Stanford University, Department of Physics. | |
| Primary advisor | Goldhaber-Gordon, David, 1972- | |
| Thesis advisor | Goldhaber-Gordon, David, 1972- | |
| Thesis advisor | Hwang, Harold Yoonsung, 1970- | |
| Thesis advisor | Toney, Michael Folsom | |
| Advisor | Hwang, Harold Yoonsung, 1970- | |
| Advisor | Toney, Michael Folsom |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Trevor Petach. |
|---|---|
| Note | Submitted to the Department of Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2017. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2017 by Trevor Anton Petach
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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