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Scanning Electron Microscopy with Samples in an Electric Field

Institute of Scientific Instruments of the ASCR, v.v.i., Královopolská 147, CZ-61264 Brno, Czech Republic
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Materials 2012, 5(12), 2731-2756; https://doi.org/10.3390/ma5122731
Received: 15 August 2012 / Revised: 16 November 2012 / Accepted: 29 November 2012 / Published: 11 December 2012
(This article belongs to the Special Issue Low Voltage Electron Microscopy)
The high negative bias of a sample in a scanning electron microscope constitutes the “cathode lens” with a strong electric field just above the sample surface. This mode offers a convenient tool for controlling the landing energy of electrons down to units or even fractions of electronvolts with only slight readjustments of the column. Moreover, the field accelerates and collimates the signal electrons to earthed detectors above and below the sample, thereby assuring high collection efficiency and high amplification of the image signal. One important feature is the ability to acquire the complete emission of the backscattered electrons, including those emitted at high angles with respect to the surface normal. The cathode lens aberrations are proportional to the landing energy of electrons so the spot size becomes nearly constant throughout the full energy scale. At low energies and with their complete angular distribution acquired, the backscattered electron images offer enhanced information about crystalline and electronic structures thanks to contrast mechanisms that are otherwise unavailable. Examples from various areas of materials science are presented. View Full-Text
Keywords: scanning electron microscopy; slow electrons; low energy SEM; low energy STEM; cathode lens scanning electron microscopy; slow electrons; low energy SEM; low energy STEM; cathode lens
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Frank, L.; Hovorka, M.; Mikmeková, Š.; Mikmeková, E.; Müllerová, I.; Pokorná, Z. Scanning Electron Microscopy with Samples in an Electric Field. Materials 2012, 5, 2731-2756.

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