Refraction Effect of Secondary Electrons
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This refraction effect of secondary electrons (SEs) is given by [1],
                refraction effect of secondary electrons --------------------------------------------------- [4828a]
 Here,        β -- the inner angle of incident electrons into the sample
                 α -- the corresponding emission angle into the vacuum.
                 Es -- the SE kinetic energy into the specimen
                 Ek -- the corresponding kinetic energy into the vacuum

Based on Equation 4828a, Figure 4828 shows the schematic of angular SE transmission function, T(α), at the specimen/vacuum (S/V) interface in polar co-ordinates when the specimen is a metal, a semiconductor and an insulator.

Schematic of angular SE transmission function, T(α), at the specimen/vacuum (S/V) interface

Figure 4828. Schematic of angular SE transmission function, T(α), at the specimen/vacuum (S/V) interface in polar co-ordinates when the specimen is a metal, a semiconductor and an insulator. The Lambert-type emission is also schematically shown for comparison. Adapted from [2]

The SE kinetic energy into the specimen, Es, is given by

                 Es = Ek+ EF + Φ (for a metal) -----------------------------------------------[4828b]

                 Es = Ek+ χ (for a semiconductor or an insulator) ----------------------------[4828c]

 Here,       EF -- Fermi energy

                Φ - - Work function

                χ -- Electron affinity

                The sum EF (Fermi energy) and Φ (Work function) for metals is often of ~10 eV.

                Electron affinity, χ, for insulators is generally less than 3 eV.

 

[1] Henke, B.L., Liesegang, J. & Smith, S.D. (1979) Soft X-ray induced secondary electron emission from semiconductors and insulators. Phys. Rev. B, 19, 3004–3021.
[2] J. Cazaux, (2005) Recent developments and new strategies in scanning electron microscopy, Journal of Microscopy, 217, 16–35.

 

 

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