Office: PAB 210
Tel: (519) 661-2111 x83390
E-mail: psimpson [at] uwo [dot] ca
Condensed matter physics
Defects in materials
My research involves manipulating materials at the nanoscale, including “defect engineering” – the use of defects to control or modify material properties.
In the area of silicon photonics (in collaboration with Prof. Lyudmila Goncharova) we create silicon nanocrystals, which can be used as light emitters.
Fibre-optic communication is used to transmit data at high speeds using light. There is a drive to develop all-optical processing, eliminating the conversion between light and electrical signals, and taking advantage of the superior speed that all-optical processing can offer. It is desirable that this capability be developed in silicon, rather than in more exotic materials, for reasons of materials cost, and compatibility with the existing highly evolved silicon processing techniques that have been developed over ~5 decades.
The vision of an all-silicon optical chip is hampered by the lack of a suitable silicon-based light source. A promising candidate for this role is silicon nanocrystals (Si-nc) formed in a matrix of silicon oxide. We grow Si-nc by ion implantation and annealing, and study the physical processes involved in the growth, and the mechanisms of luminescence including quantum confinement.I use positron annihilation as a technique to probe defects in materials. Point defects (vacancies, i.e. atoms missing from the crystal structure, and impurities) determine the electronic properties of materials used for integrated circuits. To develop new materials and processes, an understanding of defect structures and behaviour is vital, and will become more so in the future as devices are made smaller and faster. My laboratory includes a well equipped positron accelerator facility, and (in collaboration with Profs. Peter Mascher and Andy Knights, McMaster University) we are constructing a high-intensity positron facility using the McMaster Nuclear Reactor as a source of positrons for materials research. This world class facility is funded by the Canada Foundation for Innovation (CFI).