Better quality imaging is often needed for all optical instruments including the scanning electron microscope (SEM). Inside the SEM, an electron beam is generated by applying a voltage to the electron gun. The electron beam propagates through the SEM column and illuminates the specimen with a small probe. Our research is oriented towards the end goal of obtaining better images by modeling the SEM column which contains the lens system needed for probe formation. This probe which scans the specimen to produce the final image is one of the pivotal factors which determines the fundamental resolution of a SEM. We have developed a simulation program based on wave optics of the electron beam and the lens system to predict variation in electron distribution within the probe under different operating conditions for a field-emission SEM. It is crucial to note that we ensure that all input parameters to the program are well known to a standard SEM user. The program offers capabilities of introducing Seidel and parasitic aberrations in the lens aperture, effects of the partial coherence of the source, noise, etc. and predict their effects on the final probe and imaging. This kind of analytical tool would be very insightful for microscopists to critically understand the behavior of their microscopes and to potentially design experimental and computational methods to overcome these limitations to achieve better resolution.
Department, Program, or Center
School of Physics and Astronomy (COS)
Kamal, Surya, "Wave Optics in Scanning Electron Microscopy" (2021). Thesis. Rochester Institute of Technology. Accessed from
RIT – Main Campus