Transmission electron microscopy (TEM) is an invaluable tool for the study of the physics and materials properties of thin films. This thesis addresses innovations and novel applications of TEM to materials physics, and consists of three parts: the examination and development of innovative TEM sample preparation techniques, conventional selected area electron diffraction with new techniques for data extraction, and an extended TEM investigation of quantum dots.

A major source of reduction of TEM data quality is an amorphous layer which forms on the top and bottom surfaces of the TEM samples as a result of the use of ion-milling or focused ion beam (FIB) sample preparation. These artifacts cause significant degradation of the information content inTEM micrographs, particularly at high magnifications where images are collected from the thinnest regions of the sample. Here the amorphized regions may comprise a significant percentage of the entire sample thickness. Measurements of the extent of this damage and techniques to minimize it are presented and discussed.

With changing materials and requirements for analysis, new TEM techniques for specimen preparation are continually in demand. One new technique discussed is the application of the colours of silicon readily evident to the human eye, when viewed in transmission. Silicon TEM samples backlit with an optical light source display a series of colours in regions of less than 10 microns thickness and a series of interference fringes in the regions of less than 2 microns thickness. These colours and fringes result from the transmission, reflection, absorption and interference of light within the sample and depend upon the light source and sample thickness. These colours can be used as a technique for monitoring sample thickness during TEM sample preparation.

Refinements in the analysis and interpretation of TEM data are possible through the use of image digitization and numerical processing. For example, a newly observed [7 5 ] epitaxial relationship between Ni and MgO was studied by dark-field TEM and selected area electron diffraction. These films were polycrystalline and produced many diffraction spots from both the Ni film and MgO substrate. Electron diffraction patterns of the films were indexed using a new technique, Electron Diffraction Image Processing (EDIP), which was developed for this study and introduced in the resulting paper.

Confidence in the interpretation of the information acquired by TEM requires numerical modeling of the images. The ambiguity that can exist in subtle TEM diffraction contrast images is illustrated by a study of quantum dots (QDs). These structures consist of small islands that can form spontaneously after the deposition of several monolayers of highly lattice-mismatched materials. QDs behave as artificial atoms, and can be used to improve the performance of semiconductor lasers and to create new types of devices such as single electron transistors. The optical properties of QDs vary with their size, so a knowledge of the size and shape of self-assembled InAs/GaAs QDs is necessary for modeling QD formation, electronic structure and optical spectra.

When viewed by TEM, the apparent shapes of QDs in diffraction contrast images vary greatly with the precise diffraction conditions. This can lead to ambiguity in attempting to define the shapes of the QDs, particularly in plan-view where the observed contrast is primarily the result of strain. Single and multiple layers of self-assembled InAs QDs produced by the indium flush technique have been studied by TEM in an effort to develop techniques to reproducibly grow QDs of uniform size and shape. To monitor changes in QD dimensions, plan-view samples of capped single layers were studied as well as cross-sectional samples of QDs in multiple layers and vertically aligned stacks. The changes in the observed round and square QD images under various plan-view TEM imaging conditions, and the contrast reversal in the center of QD images viewed in cross-section are modeled using the many-beam Bloch-wave approach. The sizes and shapes of the QDs were determined through the interpretation of the observed (primarily strain) contrast in plan-view and the observed (primarily atomic number) contrast in cross-sectional TEM.