Real-time studies of the mechanisms of nanocrystal structural phase changes
Abstract/Contents
- Abstract
- Nanocrystals provide ideal systems with which to study structural phase changes. By making use of the ultra-short pulsed nature of synchrotrons and free-electron lasers, one may visualize with atomic-resolution and in real time how nanosized systems rearrange and potentially resolve the transition state itself. Such information could lead to new material design opportunities in which the phase-change behavior is optimal for a given application. Here are presented ultrafast studies of both temperature and pressure-driven phase changes in nanocrystalline materials, utilizing x-ray diffraction and x-ray spectroscopy to monitor the atomic rearrangement on femtosecond time-scales. For a thermally-driven phase change, the onset of superionicity is considered, a unique superposition of liquid-like cationic conductivity within a solid-phase anionic lattice. Using near-edge spectroscopy, the superionic structural transformation is observed to occur faster than twenty picoseconds in laser-excited copper (I) sulfide nanocrystals, and it is shown that it is the ionic hopping time which determines this time-scale. For pressure-induced studies, the dynamics of the well-known change of cadmium selenide nanocrystals from a wurtzite to rock-salt unit cell under increasing pressure are investigated. Laser-induced shock compression is used to initiate the phase transformation and hard x-ray scattering acts as as the probe. Finally, the efforts to introduce time-resolved capabilities at SSRL are presented. In particular, measurements of the x-ray pulse duration under different synchrotron operating conditions show the ability to perform experiments with single-picosecond resolution at SSRL. These single-photon sensitive measurements allowed the optimization of the pulse compression for future x-ray experiments at SSRL.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2012 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Miller, Timothy Alan | |
|---|---|---|
| Associated with | Stanford University, Department of Materials Science and Engineering | |
| Primary advisor | Lindenberg, Aaron Michael | |
| Thesis advisor | Lindenberg, Aaron Michael | |
| Thesis advisor | Reis, David A, 1970- | |
| Thesis advisor | Toney, Michael Folsom | |
| Advisor | Reis, David A, 1970- | |
| Advisor | Toney, Michael Folsom |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Timothy Alan Miller. |
|---|---|
| Note | Submitted to the Department of Materials Science and Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2012. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by Timothy Alan Miller
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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