Si(Li) X-Ray Detectors with Amorphous Silicon Passivation

Lithium-drifted silicon [Si(Li)] detectors with thin lithium n+ contacts and amorphous silicon (α-Si) junction passivation are described. These detectors (7 mm thick, 9 cm2 area) are intended for use in a sixelement detector array which is designed to measure trace amounts of plutonium in soil samples. Results are given showing a spectral resolution of ~ 400 eV (FWHM) for the 17.8 keV Np L x-rays entering through either the lithium n+ contact or the gold barrier contact on these detectors. Measurements on the effects of the fractional H2 concentration on the electrical behavior of the α-Si/Si interface are reported. The increase with time in the lithium window thickness when the detectors are stored at room temperature is discussed.