An alternative approach to the response function of Si(Li) X-ray detectors based on XPS study of silicon and front contact materials

In a study of various Si(Li) X-ray detectors, strong variations of the response function were observed. In order to develop a physical understanding of the details of the response function, the photoelectron and Auger electron spectra of silicon generated by copper Kα and silver Lα X-rays were measured with a high-energy, high-resolution, electron spectrometer. The electron spectra of two of the variously reported front contact materials (gold and nickel) were also studied. Correspondence between these electron spectra and various components of the Si(Li) X-ray detector response function is proposed. Unavoidable contributions to the low-energy tails of the response function of a very good quality Si(Li) X-ray detector can be derived from the measured electron spectra. The peculiarity of the 5–10 keV photoelectron spectra of Si is the large plasmon loss peaks. The obtained electron spectra provide a background for testing the individual processes in Monte Carlo simulations of Si(Li) detectors, Si drift counters and CCD detectors.