LE3 .A278 2005

2005

Robertson, Michael

Acadia University

Bachelor of Science

Honours

Physics

Physics

Quantum dots (QDs) are a hot topic in the science world today. They are expected to be part of many devices in the future, from artificial atoms to quantum computers and even going so far as “lasersâ€. Quantum dots are rather new and there is still much to learn about them in their many varieties. This thesis focuses primarily on self-assembled InAs dots in an InP matrix. This particular QD system is important for its optical properties, as these dots have a wavelength emission range of 1.2 – 2.0 μm, within which lies the important 1.55 μm telecommunications wavelength. Since the dimensions of semiconductor quantum dots are on the order of nanometres, and the electronic and optical properties of QDs depend sensitively on their size and shape, it is important to measure these physical properties precisely. Transmission electron microscopy (TEM) is currently the only technique capable of measuring the size and shape of buried QDs. In order to learn more about the properties of these dots, computers are used to simulate how QDs will look under a TEM since the image contrast generated by a TEM is often not directly interpretable. Using the insight gained from image simulations, experimental TEM images were analyzed, and the diameter and contrast (corresponding to QD height) data were fit to distributions that allowed precise size and height measurements to be made from a single plan-view specimen. The use of various approximations in the simulations was investigated and their range of validity has been estimated.

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https://scholar.acadiau.ca/islandora/object/theses:442