Imaging with electrons : unraveling nanoscale structure-function relations in energy storage & quantum optical materials
Abstract/Contents
- Abstract
- While nanoscaling offers unique tuning knobs for optimizing system performance, it also changes process fundamentals. Ensemble measurements are often convoluted due to system heterogeneity, and lacks spatial resolution into the nanoscale. How do we correlate nano-to-atomic scale structure to the system performance? My work tackles this question for two vital technologies: (1) energy storage like batteries and metal hydrides, and (2) bright single photon sources for quantum optics, communication and sensing. We leverage, modify and develop electron microscopy techniques which let us probe the system performance (H-content and reaction rates for the former, optical emission for the later) and do correlative structural analysis at the nanoscale. At first, we explore how nanoscale dimensionality changes hydrogenation phase-change thermodynamics. We find that, one-dimensional nanorods have very distinct steady-state phase-coexistence in contrast to zero-dimensional nanoparticles. We report a length range beyond which it is more likely to form defects during phase-change. Next, we focus on understanding the effect of shape and surface faceting on reaction dynamics. We develop a technique to visualize the reaction in real-time in-situ using diffraction contrast. Capitalizing on this, we find that the phase-change is a nucleation-growth process. Nuceation always occurs at the corner irrespective of shape, but phase-propagation direction depends on shape. We also do structural analysis of reaction intermediates, and find that while rotational defects are likely to form during phase-transition, the particles 'self-heal' at the end. Next, we focus on developing single photon sources in a van der Waals insulator: hexagonal boron nitride (hBN). The biggest question circumventing technological development of hBN is the origin of spectral variability of emission. We develop a technique to correlate the defects' cathodoluminescence (CL) in a transmission electron microscope and photoluminescence (PL) in an optical microscope. Using this, we localize each defect with 15−20 nm resolution. Based on PL-CL correlation and local strain of the local host environment using electron diffraction, we postulate that there are at least four different atomic defects resulting into the observed spectral variability. Together, our results pushes the field towards direct identification of these defects and achieve 'designer-defect' and emission properties
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 | 2020; ©2020 |
| Publication date | 2020; 2020 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Hayee, Fariah |
|---|---|
| Degree supervisor | Dionne, Jennifer Anne |
| Thesis advisor | Dionne, Jennifer Anne |
| Thesis advisor | Fan, Jonathan Albert |
| Thesis advisor | Vuckovic, Jelena |
| Degree committee member | Fan, Jonathan Albert |
| Degree committee member | Vuckovic, Jelena |
| Associated with | Stanford University, Department of Electrical Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Fariah Hayee |
|---|---|
| Note | Submitted to the Department of Electrical Engineering |
| Thesis | Thesis Ph.D. Stanford University 2020 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2020 by Fariah Hayee
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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