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Lock‐in technique applied to cathodoluminescence of biomedical specimens in the SEM
Author(s) -
Bröcker W.,
Hauck G.,
Wefgelt H.,
Pfefferkorn G.
Publication year - 1981
Publication title -
scanning
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.359
H-Index - 47
eISSN - 1932-8745
pISSN - 0161-0457
DOI - 10.1002/sca.4950040401
Subject(s) - cathodoluminescence , scanning electron microscope , lock (firearm) , materials science , detector , optics , wavelength , amplifier , noise (video) , microsecond , protein filament , optoelectronics , physics , computer science , luminescence , composite material , image (mathematics) , engineering , mechanical engineering , cmos , artificial intelligence
Abstract Very low signals or disturbances by unwanted, foreign signals often lead to a restriction in the application of the cathodoluminescence (CL) method in the scanning electron microscope (SEM). This is even true if one uses an optimal CL detection system. We, therefore, introduced the lock‐in‐amplification technique, which has proved very successful in investigations of semiconductor materials into the biomedical field. After attaching the lock‐in system to our SEM which has a special CL equipment, we found that this technique could remove the disturbance caused by the light emitted from the heated filament, which can be reflected into the CL detector. Specimens on polished Al‐stubs or on Au‐coated glass slides could be imaged with improved contrast. The same was true if we measured the wavelengths of the CL. A general improvement of the signal‐to‐noise ratio in all specimens could not be detected. However, the beam current could often be reduced when using the lock‐in technique without a decrease in the quality of the CL image. A disadvantage of the commercially available lock‐in amplifier is that pictures need a longer exposure time than without lock‐in amplification.

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