Determining The Energy Response Of A Silicon Surface-Barrier Detector To Incident 3-Kev To 25-Kev Electrons

An energy-sensitive silicon surface-barrier detector is employed to measure the number of secondary electrons emitted during a collision between an energetic macromolecular ion and a surface. Each extracted secondary electron impacts the detector with energy U, but due to backscattering and other effects, only energy etaU is deposited in the detector. The electron energy deposition function, eta = eta(U) less-than-or-equal-to 1, is not well known for the 3- to 25-keV energies employed in our setup. In this paper, eta(U) is measured with a specially developed compact electron-pulse source placed at variable potential relative to the detector. For a particular detector, it was found that eta(U) = k(1 - 1.59/ square-rootU), where U is in units of keV. Although the proportionality constant k is not directly determined in this experiment, an estimate of k almost-equal-to 1.35 was calculated by combining literature values of the electron transmission probability of the detector gold window and the electron backscattering coefficient for silicon for 20 keV electrons.