Practical Electron Microscopy and Database

The secondary electrons (SEs) are known to be emitted with a cosine polar distribution normal to the emitting surface. Therefore, the initial SE (secondary electrons) angular-distribution as SEs leave the emitting surface is predicted to follow a cosine distribution [1]
                        ----------------------------------------------- [4832]
where,
         δ₀ -- the SE yield at α = 0°.
         α -- the angle from the normal of the emitting surface.

Figure 4832a shows the SE angular-distribution for our polycrystalline gold sample at electron beam energy of 1.5 keV.

Figure 4832a. SE angle-resolved yield data for polycrystalline Au with electron beam energy of 1.5 keV.
The curve fits the data using the cosine distribution of Equation [4832]. [2]

Figure 4832b shows the radial spread of emission of secondary electrons from a point source. Here, it shows cartesian coordinates on the sample surface.

Figure 4832b. Radial spread of emission of secondary electrons from a point source. Here, cartesian coordinates is used on the sample surface.

SE angular-distributions can be measured with a rotatable Faraday cup retarding field analyzer for a range of fixed emission angles between -18° and +73° with respect to the sample normal [2].

[1] J. H. L. Jonker, The angular-distribution of the secondary electrons of nickel, Philips Res. Rep., 6, 372-387,1951.
[2] N. Nickles, R. E. Davies and J. R. Dennison, Applications of Secondary Electron Energy- and Angular-Distributions to Spacecraft Charging, 6th Spacecraft Charging Technology Conference, AFRL-VS-TR-20001578, 1 September 2000.