Measurement of the low energy tail spectra adjacent to the x-ray photopeak in Si(Li) x-ray detectors

Abstract

Low energy tail spectra, which are inherently observed adjacent to the X-ray photopeak in the use of a Si(Li) X-ray detector, have been measured for the 1.3–3.7 keV X-ray energy range. Three different Si(Li) detectors have been tested. The tail/peak count ratios as a function of incident X-ray energy have exhibited a rapid change at the boundary energy of the Si K absorption edge. From the observed tail/peak count ratios, the thickness of the Si layer which produces the tail spectrum has been estimated; the thicknesses for the three tested detectors are about 0.05, 0.1 and 0.2 μm. In addition to the carrier diffusion effect, it is proposed in the case of a Si(Li) detector that the effect of the escape (penetration) of Auger and phtoelectrons from (into) the intrinsic region plays an important role in the production of the tail spectra.