Imaging Results from a Direct Conversion X-ray Detector with TlBr and CMOS Pixel Array

This work explores the fabrication and characterization of X-ray imaging devices using a single-crystal TlBr sample (8 mm × 8 mm × 10 mm) and polycrystalline TlBr film (approximately 0.38-mm thick), both bonded to a Libra-1 Complementary Metal-Oxide-Semiconductor (CMOS) readout chip connected to the BrillianSe 1M readout system. The BrillianSe 1M, designed for X-ray radiography by KA Imaging, features a 10 mm × 11 mm readout chip with a 7.8 μm pixel pitch and a 7.8 mm × 7.8 mm active area. The work below describes the characterization of test and imaging devices. The characterization includes current-voltage (IV) curves and impedance spectra, longevity measurements of the X-ray response and leakage current, and imaging characterization with light-emitting diodes (LED) and X-rays. The resistivity of 3x10¹⁰ Ω-cm was estimated for a polycrystalline film sample. Following five weeks, the leakage current decreased from 670 to 6.4 nA, while the X-ray photocurrent decreased from 28 to 4 nA. Both the single crystal and polycrystalline imaging devices resolved 0.3-mm-diameter holes in a Tungsten composite mask when irradiated with 90 kVp (100 μA tube current) X-rays. Effects at the interface can be seen with both LED and X-rays. The images provide critical information for optimizing the fabrication process and device longevity.