DIRS Laboratory 76-3215
April 26, 2019 at 1:00pm
Mandy Nevins
Ph.D. Thesis Defense
Abstract: 

Electron microscopes have the capability to examine specimens at much finer detail than a traditional light microscope. Higher electron beam voltages correspond to higher resolution, but some specimens are sensitive to beam damage and charging at high voltages. In the scanning electron microscope (SEM), low voltage imaging is beneficial for viewing biological, electronic, and other beam-sensitive specimens. However, image quality suffers at low voltage from reduced resolution, lower signal-to-noise, and increased visibility of beam-induced contamination. Most solutions for improving low voltage SEM imaging require specialty hardware, which can be costly or system-specific. Point spread function (PSF) deconvolution for image restoration could provide a software solution that is cost-effective and microscope-independent with the ability to produce image quality improvements comparable to specialty hardware systems. Measuring the PSF (i.e., electron probe) of the SEM has been a notoriously difficult task until now. The goals of this work are to characterize the capabilities and limitations of a novel SEM PSF determination method that uses nanoparticle dispersions to obtain a two-dimensional measurement of the PSF, and to evaluate the utility of the measured PSF for restoration of low voltage SEM images. The presented results are meant to inform prospective and existing users of this technique about its fundamental theory, best operating practices, the expected behavior of output PSFs and image restorations, and factors to be aware of during interpretation of results.