Recent developments in the understanding and application of backscattered and secondary electrons in the SEM

摘要

The secondary electron and backscattered electron coefficients have been measured as a function of primary beam energy for as-inserted and cleaned pure element samples. Clearly, the effect of cleaning samples makes a significant effect on both these key measurements needed for understanding the electron transport measurements in scannng electron microscopy and a number of other technologies. The results from the cleaned samples suggest that the currently accepted theory for secondary electron emission (SEE) of Baroody does not take account of an important physical effect. We propose that the SEE in transition metals is mainly controlled by the inelastic mean free path (IMFP) of the secondary electrons. In combination with current theories on the transport of hot electrons in transition metals, where sensitivity to the density of empty d states is important, the apparent correlation of the work function with SEE can be explained. The effect of errors in the electron elastic scattering cross-section and the electron stopping power on the estimates of backscattered electron coefficient, η, are explored for the case of Cu. It is found that percentage errors in one parameter (e.g. stopping power) cause very similar changes in r) as equal but opposite percentage errors in the other parameter (e.g. elastic scattering cross-section).