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Low-cost scanning electron microscope

University of British Columbia

For decades, the scanning electron microscope (SEM) has been a workhorse of imaging in academic and industrial environments. The inherent properties of the high-energy electron beams used in SEMs allow for high-resolution imaging with a large depth of focus, making SEMs important analysis tools for life sciences, materials engineering, and microelectronics. As highly sophisticated and complex instruments, SEMs have been prohibitively expensive for many applications since their initial commercialization in the 1960s. Current SEM technology also has limitations in terms of the complexity of operation, time consuming sample preparation, large space requirements, high power consumption, and long analysis times. The work presented in this thesis describes progress towards the making of a low-cost SEM (LCSEM) to address the seemingly intrinsic limitations of current SEM technology. The LCSEM system involves a complete rethinking of the traditional SEM in terms of the electron source, vacuum chamber, electron optics, and scanning technology. An optically stimulated carbon nanotube forest-based electron source has been experimentally verified to be a suitable cathode with a small and adjustable electron emission area. A permanently sealed vacuum chamber has been engineered with an electron-transparent membrane acting as an objective aperture for imaging a sample held at atmospheric pressure. A permanent magnetic objective lens and electromagnetic beam alignment assembly have been built and characterized for a simple, low power electron optical column. A mechanical sample scanning stage, based on a modified optical image stabilizer, has been used to scan the sample with respect to the stationary electron beam, enabling image generation using a web application on a smart device. The entire system has been integrated into a compact, industrially designed prototype that demonstrates the LCSEM with microscale resolution in transmission-mode imaging in atmosphere.

Text

2025-04-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/74005

Electrical and Computer Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/