Structural phase stability and van der Waals computation for two-dimensional materials
Abstract/Contents
- Abstract
- Two-dimensional (2D) materials are a family of materials that are atomically thin, with ultra-high surface-to-volume ratio. Multiple 2D materials can be held together by van der Waals interaction to build layered heterostructures. Since the first experimental isolation of a 2D material graphene in 2004, 2D materials have attracted much attention as promising candidate materials for future nanoscale devices. In the first part of the dissertation, I focus on a unique property of a small subset of 2D transition metal dichalcogenide (TMD) monolayers: the potential to exist in multiple competing crystal structures. Phase change materials have wide spread applications from electronics, optics to energy technology. Here, I study the structural phase stability control of a TMD monolayer, MoTe2 monolayer, with surface adsorption of atoms and molecules. Our density functional theory (DFT) calculations reveal the potential for surface adsorption to induce a structural phase change between the competing semiconducting and metallic crystal structures of the monolayer. Further, I find that the MoxW1-xTe2 monolayer alloy composition can be tuned to achieve some degree of molecular selectivity in phase changes, providing a basis for nanoscale molecular sensing applications. I next focus on van der Waals computation for 2D materials. As an alternative to expensive standard electronic-structure approaches, I explore the potential for an electromagnetic approach to describe van der Waals interactions to provide faster computation for layered materials, including some non-pairwise effects which may be important for layered materials. Surprisingly, we find that this electromagnetic approach, based on a modified Lifshitz model, combined with DFT calculations of optical properties can provide total van der Waals interaction energies within 8-20% of the advanced electronic structure calculations for a variety of layered heterostrctures. This method potentially provides a powerful tool for studying van der Waals interactions in layered heterostructure devices. Finally, I applied our defined Lifshitz model to study surface wettability of 2D materials and their layered forms. The literature contains a wide variation of reported water contact angles for graphene, postulated to be associated with contaminations. However, a theoretical understanding of this variation has yet to be quantitatively fully explored. Here, I utilized the Lifshitz model to find that certain forms of contamination can indeed induce the large variation in reported water contact angles for layered materials. I also make predictions on layer dependence and substrate dependence of wettability.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2018; ©2018 |
| Publication date | 2018; 2018 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Zhou, Yao |
|---|---|
| Degree supervisor | Reed, Evan J |
| Thesis advisor | Reed, Evan J |
| Thesis advisor | Cai, Wei, 1977- |
| Thesis advisor | Lindenberg, Aaron Michael |
| Degree committee member | Cai, Wei, 1977- |
| Degree committee member | Lindenberg, Aaron Michael |
| Associated with | Stanford University, Department of Materials Science and Engineering. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Yao Zhou. |
|---|---|
| Note | Submitted to the Department of Materials Science and Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2018. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2018 by Yao Zhou
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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