Defect Engineering in Metal Oxide Through Laser Irradiation
| dc.contributor.author | Zheng, Shuo | |
| dc.date.accessioned | 2024-06-14T19:08:16Z | |
| dc.date.issued | 2024-06-14 | |
| dc.date.submitted | 2024-06-11 | |
| dc.description.abstract | Metal oxides such as copper oxide (CuO), titanium dioxide (TiO2) and zinc oxide (ZnO) are one of the most important and broadly-studied classes of semiconductors. Their nano-materials have shown great potential in the development of functional nano-devices. In metal-oxide nano-materials, zero-dimensional point defects are believed to play a central role in the control and optimization of their properties because they would be strongly determined by the nature, concentration and arrangement of these point defects. Therefore, tailoring the properties of metal-oxide nano-materials for targeted applications through engineering these characteristics of defects is of growing interest. Laser irradiation, as one of the emerging technologies, has shown the ability of engineering point defects in metal-oxide nano-materials through. However, the information on the characteristics of these laser-induced defects remains limited and further investigations are highly required to understand the defects related properties and how the defects can be introduced. In this thesis, the following research works were demonstrated. The CuO nanowires (NWs), one of the most popular p-type metal-oxide nano-materials, were prepared by thermal oxidation and irradiated by ns laser. The produced defects resulted in intragap energy levels that narrow the bandgap of CuO, which gives rise to improved absorption in the visible region. The concentration of defect centers after laser irradiation increases electrical conductivity by a factor of two at a forward bias of 15 V and enhances photo-conductivity of the Au/CuO/Au structure, tripling the optical gain of these structures. Besides, the concentration of defects was also successfully tailored in ZnO, an n-type metal oxide. The defect-to-lattice ratio of oxygen species can be tuned in a range between 0.24 and 0.61. The increased concentration of defects in ZnO thin films resulted in narrowed bandgap energies and extended the photo-response of these ZnO thin films into the visible region. Next, the control over the distribution of these defects was explored. CuO NW films were grown and surface defects were introduced through laser irradiation, which were verified by electrochemical measurements. Further control over the arrangement of the defects was demonstrated in ZnO NWs. ZnO NWs with abundant defects locating at the surface regions (within 1.5 nm from the surface) and residing in the region as deep as 6 to 12 nm were obtained, respectively. The surface-to-bulk ratio of defects in ZnO NWs can thus be modulated by tuning the laser fluence and exposure time. ZnO NWs with abundant surface defects showed enhanced photodegradation rate of dye molecules while the ZnO NWs with more bulk defects exhibited less efficiency. Lastly, the type of defects was tailored in Cu2O and ZnO thin films through laser irradiation under different atmosphere conditions. Either oxygen-rich or oxygen-poor ambient conditions were provided during laser irradiation so that corresponding cationic or anionic vacancies can be generated. The formation of V_O in Cu2O and V_Zn in ZnO thin films leads to the abnormal conductivity types in these materials, resulting in n- and p-type doping respectively. Thin film transistors with complementary conducting channels were then fabricated in Cu2O and ZnO thin films with laser induced defects to show the efficacy of this laser doping process. Overall, the investigation of defect engineering in metal-oxide nano-materials through laser irradiation is still limited and requires more effort. Some of the remaining research questions and potential research studies are stated in the last chapter of this thesis to inspire future research activities. | en |
| dc.identifier.uri | http://hdl.handle.net/10012/20654 | |
| dc.language.iso | en | en |
| dc.pending | false | |
| dc.publisher | University of Waterloo | en |
| dc.subject | laser processing | en |
| dc.subject | defect engineering | en |
| dc.subject | metal oxide nanomaterials | en |
| dc.subject | zno | en |
| dc.subject | cuo | en |
| dc.subject | oxide-TFT | en |
| dc.title | Defect Engineering in Metal Oxide Through Laser Irradiation | en |
| dc.type | Doctoral Thesis | en |
| uws-etd.degree | Doctor of Philosophy | en |
| uws-etd.degree.department | Mechanical and Mechatronics Engineering | en |
| uws-etd.degree.discipline | Mechanical Engineering | en |
| uws-etd.degree.grantor | University of Waterloo | en |
| uws-etd.embargo | 2026-06-14T19:08:16Z | |
| uws-etd.embargo.terms | 2 years | en |
| uws.contributor.advisor | Zhou, Norman | |
| uws.contributor.advisor | Peng, Peng | |
| uws.contributor.affiliation1 | Faculty of Engineering | en |
| uws.peerReviewStatus | Unreviewed | en |
| uws.published.city | Waterloo | en |
| uws.published.country | Canada | en |
| uws.published.province | Ontario | en |
| uws.scholarLevel | Graduate | en |
| uws.typeOfResource | Text | en |
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