Synthesis and Characterization of Amorphous Selenium Alloys Radiation Detectors

Synthesized amorphous selenium (a-Se) alloy materials have been characterized for room temperature high-energy nuclear radiation detectors and x-ray detection applications. The alloy composition has been optimized to ensure good charge transport properties and detector performance. The synthesis of a-Se (As, Cl) alloys has been carried out by thoroughly mixing zone-refined (ZR) Se (~7N) with previously synthesized a-Se (As) and a-Se (Cl) master alloys (MS). The synthesized alloys have been characterized by x-ray diffraction (XRD), glow discharge mass spectroscopy (GDMS), differential scanning calorimetry (DSC), x-ray photoelectron spectroscopy (XPS), and current-voltage (I-V) measurements. Raman spectroscopy demonstrated that the a-Se (As) master alloy samples were in metastable monoclinic Se₈ states, in which seven vibrational modes are identified at 40, 59, 77, 110, 133, 227 and 251 cm^-1. However, a-Se (Cl) master alloy samples are in stable form of trigonal structure of Se₈ ring, in which two modes at 142 and 234 cm^-1 were found. Both Raman and energy dispersive spectroscopy (EDS) exhibited that a small amount of tellurium (Te) existed in a-Se (As, Cl) master alloy samples. DSC measurements showed that a-Se (Cl) MS and a-Se (As) MS samples have one melting point, located at ~219.6 °C, whereas a-Se-As (0.52%)-Cl and Se-As (10.2%)-Cl (60 ppm) possess melting points at 221 and 220.3 °C respectively. The a-Se alloy detectors have been fabricated and tested and the results showed dark resistivity (10¹² - 10¹³ Ω-cm) with good charge transport properties and cost-effective large-area scalability.