Direct Deposition of Microcolumnar Scintillator on CMOS SSPM Array: Toward a Photon Counting Detector for X‐Ray/Gamma Ray Imaging

We are developing a modular, low‐cost, photon‐counting detector based on a scintillator coupled to a solid‐state photodetector. A working prototype was successfully developed by depositing CsI:Tl directly onto a CMOS SSPM array designed by RMD and custom‐fabricated by a commercial foundry. The device comprised a 6×6 array of 1.5×1.5 mm2 macro‐pixels, each containing a 36×36 array of resistively coupled micro‐pixels, that was subjected to vapor deposition of columnar CsI:Tl. Direct deposition eliminates the gap between the scintillator and SSPM and creates a better optical bond than does index‐matching grease. This paper compares the performance of SSPMs with directly deposited CsI:Tl, in terms of signal‐to‐noise ratio and light spread, against devices using monolithic single crystals or pixelated single crystals coupled to the SSPM. Due to the reduction in light scattering and optical losses in the interface, the directly deposited CsI:Tl demonstrated significantly better position sensitivity, with at lea...