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Permanent link (DOI): https://doi.org/10.7939/R3J097

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Advanced methods in Glancing Angle Deposition to control thin film morphology, microstructure and texture Open Access

Descriptions

Other title
Subject/Keyword
microstructure
nanostructure
nanorod
zinc oxide
photovoltaic
semiconductor
Fe
nanotechnology
ZnO
crystal texture
FeS2
thin film
iron
nanocolumn
morphology
glancing angle deposition
iron pyrite
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
LaForge, Joshua M
Supervisor and department
Brett, Michael (Electrical and Computer Engineering)
Examining committee member and department
Sit, Jeremy (Electrical and Computer Engineering)
Hegmann, Frank (Physics)
Dost, Sadik (University of Victoria, Mechanical Engineering)
Chen, Jie (Electrical and Computer Engineering)
Department
Department of Electrical and Computer Engineering
Specialization
Micro-Electro-Mechanical Systems (MEMS) and Nanosystems
Date accepted
2013-11-05T11:24:55Z
Graduation date
2014-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Structuring of material on the nanoscale is enabling new functional materials and improving existing technologies. Glancing angle deposition (GLAD) is a physical vapor deposition technique that enables thin film fabrication with engineered columnar structures on the (10 to 100) nm scales. In this thesis, we have developed new methods for controlling the morphology, microstructure, and texture of as-deposited GLAD films and composite films formed by phase transformation of GLAD nanocolumn arrays during post-deposition annealing. These techniques are demonstrated by engineering the vapour flux motion in both Fe and ZnO nanorod deposition and FeS2 sulfur-annealing. Crystalline Fe nanorods with a tetrahedral apex can be grown under rapid continuous azimuthal rotation of the substrate during growth. Discontinuous azimuthal rotation with 3-fold symmetry that matches the nanocolumn's tetrahedral apex symmetry produces nanocolumns with in-plane morphological and crystal orientation. This method, called flux engineering, provides a general approach to induce biaxial crystal texture in faceted GLAD films. Similar effects were found for ZnO nanocolumns. Reliable production of photovoltaic-grade iron pyrite thin films has been challenging. Sulfur-annealing of bulk films often produces cracking or buckling. We used the flux-engineering processes developed for Fe to control the inter-column spacing of the precursor film. By precisely tuning the inter-column spacing of the precursor film we can produce iron pyrite films with increased crystallite sizes >100 nm with a uniform, crack-free, and facetted granular microstructure. Large crystallites may reduce carrier recombination at grain boundaries, which is attractive for photovoltaic cells. We assessed the viability of these films for photovoltaic applications with composition, electrical, and optical characterization. Notably, we found a 27 ps lifetime of photocarriers measured with ultrafast optical-pump/THz-probe and tested charge-separation characterization between the pyrite films and a conjugated polymer with absolute photoluminescence quenching measurements. These results provide the foundation for future improvements in pyrite processing for photovoltaic cells.
Language
English
DOI
doi:10.7939/R3J097
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
LaForge, J. M., Gyenes, B., Xu, S., Haynes, L. K., Titova, L. V., Hegmann, F. A., & Brett, M. J. (2013). Tuning iron pyrite thin film microstructure by sulfurization of columnar iron precursors. Solar Energy Materials and Solar Cells, 117, 306–314. doi:10.1016/j.solmat.2013.06.028 LaForge, J. M., Ingram, G. L., Taschuk, M. T., & Brett, M. J. (2012). Flux Engineering To Control In-Plane Crystal and Morphological Orientation. Crystal Growth & Design, 12(7), 3661–3667. doi:10.1021/cg300469s LaForge, J. M., Taschuk, M. T., & Brett, M. J. (2011). Glancing angle deposition of crystalline zinc oxide nanorods. Thin Solid Films, 519(11), 3530–3537. doi:10.1016/j.tsf.2011.01.241

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