Simulations of Si(Li) x-ray detector response

Si(Li) lineshapes are generated using a model that incorporates Monte Carlo simulation of the interactions of the incident photon, a very simple approach to energy deposition by the primary (Auger and photo-) electrons, and an analytical approximation for diffusion of thermalized. secondary electrons. The aim of the work is illustrative rather than quantitative. Interactions in the metal contact produce various spectrum artefacts, and interactions in the silicon produce a low-energy shelf structure with well-defined steps that have recently been observed experimentally but that are not mentioned in previous Monte Carlo simulation work, although they are to be expected on the basis of electron transport. Details of this structure are strongly influenced by pulse processing time in the electronic system. Artefacts arising from a silicon dead layer can enhance the escape peak intensity, and can assist in estimating this layer's thickness. Inclusion in the simulation of Goto's model for secondary electron diffusion, incorporating reflection at the metal-Si interface, results in a truncated low-energy shelf, whose threshold energy is determined by the reflection coefficient; its intensity can also be predicted from an earlier, simple, analytical model that combines finite, primary, electron range effects with carrier losses in a region of incomplete charge collection whose thickness is well defined. Copyright (C) 2001 John Wiley & Sons, Ltd.