Dynamics and effects of induced surface atomic defects in photocatalytic metal-oxide semiconductors
File(s)
Author(s)
Glass, Daniel
Type
Thesis
Abstract
Metal-oxide semiconductors are some of the most extensively studied materials across a broad range of commercial applications. However, for many important industrial processes, such as photocatalytic reactions, the role defects play within these materials is generally not very well understood. Point defects in metal-oxide semiconductors, specifically oxygen vacancies, are some of the most reactive sites. Even in such low concentrations on the order of parts per million defects can have significant impacts on materials, altering the chemical, physical and electronics properties. Yet, vacancy defects are also notoriously hard to detect. While a range of techniques currently exist to probe vacancies these often require far from reaction conditions, i.e., single crystal flat substrates, ultra-high vacuum or cryogenic conditions and specifically for photo-catalysis in the absence of photo-irradiation. Hence, an alternative method is required in order to probe vacancy defect within practical substrates under reaction conditions. In this thesis the dynamics and effects of photo-induced surface oxygen vacancies are probed using a simple technique, photo-induced enhanced Raman spectroscopy (PIERS). Through monitoring changes in the Raman band intensity of probe molecules deposited on metal-oxide semiconductor substrates over time valuable information regarding the stability of oxygen vacancies at ambient pressure under reaction conditions can be extracted. Furthermore, the measured Raman enhancement correlates to the concentration of induced vacancy defects. A summary of surface defects, metal-oxide semiconductor substrates for Raman applications and in depth PIERS studies are presented in this work. In addition, this thesis includes further studies designed to move PIERS towards different practical applications.
Version
Open Access
Date Issued
2021-07
Date Awarded
2021-11
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Maier, Stefan
Sapienza, Riccardo
Sponsor
Defence Science and Technology Laboratory (Great Britain)
Grant Number
DSTLX‐1000116630
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)