Knowledge of X-ray production as a function of depth by electrons (𝜙(𝜚z) curves) is important in quantitative electron probe microanalysis and other electron beam technologies. Extensive measurements of such curves have been made for electron energies between 6 and 30 keV and for many X-ray lines and matrix elements. Two experimental techniques based on measurements on sandwich or wedge shaped specimens have been used.
A number of expressions have been used to model 𝜙(𝜚z) curves from a square function through complicated polynomial expressions. Recently, a Gaussian model has been proposed which accurately reflects the shape of the 𝜙(𝜚z) curves and which can be linked to theoretical models. Generalizing the equation to the situation of non-normal electron incidence would appear possible.
Brown, J. D.
"Modeling of Depth Distribution of X-Ray Production,"
Scanning Electron Microscopy: Vol. 1982
, Article 11.
Available at: https://digitalcommons.usu.edu/electron/vol1982/iss1/11