A new hemispherical retarding field energy analyser for quantitative voltage measurements in the SEM

A retarding field energy analyser for quantitative voltage measurements which functionally connects a uniform extracting field with a hemispherical analysing field is described. The design principles are : (i) the centres of the hemispherical grids are to be put on the virtual source from which the secondary electron seems to come straight ahead; (ii) the radii of the hemispherical grids are to be chosen as large as possible within a restricted working distance in a scanning electron microscope; (iii) all the analysed secondary electrons are to be collected. The accuracy of the voltage measurement has been improved by a factor of 10 compared with that in the plane-parallel retarding field energy analyser.