Abstract
This thesis examines problems in phase retrieval and resolution improvement in transmission electron microscopy. It begins with the study of phase and the phase problems in microscopy. In this context a number of methods of phase retrieval are introduced and evaluated. The maximum entropy de-convolution method (MEM) is employed to solve the transport of intensity equation (TIE) for phase retrieval problems. . The theoretical basis of this method is presented along with its potential applications in the quantitative phase analysis of porous low-k dielectric materials and of p-n junction profiles in advanced IC devices using a transmission electron microscope. Using the phase retrieval method as an essential tool, the thesis continues with a study of aberration corrected and exit wave reconstructed problems. As the aberration corrected exit wave is closely related to the structure of object this technique of exit wave reconstruction can be referred as a “direct method” in real space. The direct method in real space involves the use of a novel method to retrieve the phase in the image plane using Transport of Intensity Equation/Maximum Entropy Method (TIE/MEM) and exit wave reconstruction by self-consistent propagation. Since the exit wave is restored from the complex signal in the image planes, no image model between the exit wave and image is assumed. Finally the structural information in the reconstructed exit wave is then further extended by a “complex” maximum entropy method as a direct method in reciprocal space to extrapolate the phase to higher frequencies.