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Low-Loss Electron Imagine for Enhanced Surface Detail in the Scanning Electron Microscope: The Contributions of Oliver C. Wells

Published

Author(s)

Michael T. Postek, Andras Vladar

Abstract

Low-loss electron (LLE) imaging in the scanning electron microscope (SEM) is based on the collection of energy-filtered backscattered electrons that have undergone minimal elastic interactions within a sample and therefore can carry high-resolution, surface-specific information. The earliest known record of the LLE technique was its introduction in a 1971 Applied Physics Letters communication authored by Oliver C. Wells [3]. That LLE paper followed a communication the previous year [4] describing the contrast mechanisms of the collected backscattered electrons at various take-off angles. Wells put the concepts presented in the 1970 paper together with a statement he credited to McMullan 1953, that the signal collected in the SEM could be "...restricted to the electrons which have lost only small amounts of energy and which have therefore travelled only short distances through the specimen” [5]. Therefore, low loss electron collection likely evolved from those two concepts. Wells and his co-workers carried LLE forward to become a viable imaging technique; they developed the theory, designed and assembled a working LLE detector capable of demonstrating that concept. For many years, Wells researched and refined the LLE technique to fulfill his vision of collecting the highest resolution surface information possible from the SEM. He also promoted the LLE to the scientific community and many of the instrument manufacturers (Figure 1).
Citation
Microscopy Today

Keywords

Backscattered electrons, metrology, scanning electron microscope, SEM, nanomanufacturing, low loss electrons, standards

Citation

Postek, M. and Vladar, A. (2015), Low-Loss Electron Imagine for Enhanced Surface Detail in the Scanning Electron Microscope: The Contributions of Oliver C. Wells, Microscopy Today, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=917444 (Accessed April 20, 2024)
Created January 7, 2015, Updated February 19, 2017