Calculated effects of work function changes on the dispersion of secondary electron emission data: Application for Al and Si and related elements

The published secondary electron yield (SEY) data, delta = f(E degrees), are characterized by a poor level of agreement, rarely more than 25% and lower for a common element such as Al. Some possible sources of discrepancies are related to sample preparation, leading to differences in surface composition (contamination and oxidation). This is theoretically explored by a quantitative estimate of a change of the work function, phi (or electron affinity, chi), on the escape probability, A, of secondary electrons (SEs) and consequently on the SEY data of clean and oxidized samples. An electron-stimulated reduction effect may also explain the change of the SEY with the incident electron dose (fluence). Deduced from analytical expressions for the SE angular and energy distributions, partial derivative delta/partial derivative alpha and partial derivative delta/partial derivative E-k, respectively, the present investigation also includes instrumental effects due to work function differences when a partial angular collection of SEs is conducted. Although it is illustrated here for Al and Si, the present methodology may be applied to any type of sample of known physical characteristics. Practical strategies for use in SEY measurement and in scanning electron microscopy are indicated. (C) 2011 American Institute of Physics. [doi:10.1063/1.3608046]