Si(Li) detector

One of the energy-dispersive X-ray detector used for EDS. A lithium (Li)-doped silicon single-crystal semiconductor is used as a detector element. When X-rays enter the detector element, electron-hole pairs (their generation energy is approximately 3 eV) are generated in the detector element, whose number is proportional to the energies of the X-rays. The generated electrons are collected to the anode at the bottom of the detector element by applying an external electric field. That is, the X-ray energies are measured as electric voltage pulses. Detectable elements range from boron (B: 0.18 keV @K line) to uranium (U: 3.16 keV @M line). The energy resolution of the detector is approximately 140 eV (@Mn K line). Cooling of the detector by liquid nitrogen is required to prevent diffusion of doped Li and to reduce a dark current caused by thermal noise. Owing to the development of a silicon drift detector (SDD) which has a high count rate and can be used by Peltier cooling, the Si(Li)detector has less been used.

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