Electrical, mechanical, and optical characterization of two-dimensional materials with molecular overlayers
Abstract/Contents
- Abstract
- A two-dimensional object is entirely surface, with no interior. Its immediate surroundings will accordingly influence its response to electrical, mechanical, and optical stimuli. This thesis explores two different two-dimensional electron systems with molecular overlayers: the surface electron liquid in strontium titanate induced by electrolyte gating, and graphene decorated by ordered adsorbates. Strontium titanate is a band insulator that goes superconducting when doped with remarkably few electrons. By accumulating positive ions at a strontium titanate surface, the electrolyte gating technique can create a two-dimensional electron system with gate-tunable superconductivity. I combine an electrolyte gate with nanopatterned metal-oxide gates to realize the first gate-tunable superconducting weak link in this promising correlated electron system. With the same technique I create a ballistic one-dimensional channel in strontium titanate, and use this channel to perform in-plane tunneling spectroscopy of the superconducting state. Finally, using strontium titanate as a test case, I describe a method to improve mobility of generic electrolyte-gated surface systems by protecting the channel with a thin layer of hexagonal boron nitride. In the second part of this thesis, I use high-resolution atomic force microscopy to reveal a nanotexture that unexpectedly forms on flakes of graphene (and boron nitride) prepared in laboratory air: a "superlattice" of topographic stripes whose period is 4 nm. I argue that these stripes are self-assembled environmental adsorbates, and show that they are responsible for graphene's strongly anisotropic friction--a property previously believed to result from periodic rippling of the graphene sheet itself. In agreement with this self-assembly picture, I demonstrate that the local axis of high friction can be patterned with submicron precision by appropriate mechanical contact. I further show that the stripes produce anisotropic optical response, and I discuss the potential influence of the stripe-superlattice on graphene's electronic properties.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Gallagher, Patrick |
|---|---|
| Associated with | Stanford University, Department of Physics. |
| Primary advisor | Goldhaber-Gordon, David, 1972- |
| Thesis advisor | Goldhaber-Gordon, David, 1972- |
| Thesis advisor | Heinz, Tony F |
| Thesis advisor | Moler, Kathryn A |
| Advisor | Heinz, Tony F |
| Advisor | Moler, Kathryn A |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Patrick Gallagher. |
|---|---|
| Note | Submitted to the Department of Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Patrick Raam Gallagher
Also listed in
Loading usage metrics...