Polycrystalline Mercuric Iodide Films on CMOS Readout Arrays

We have created high-resolution x-ray imaging devices using polycrystalline mercuric iodide (HgI₂) films grown directly onto CMOS readout chips using a thermal vapor transport process. Images from prototype 400 times 400 pixel HgI₂-coated CMOS readout chips are presented, where the pixel grid is 30 mum times 30 mum. The devices exhibited sensitivity of 6.2 muC/Rcm² with corresponding dark current of ~2.7 nA/cm², and a 80 mum FWHM planar image response to a 50 mum slit aperture. X-ray CT images demonstrate a point spread function sufficient to obtain a 50 mum spatial resolution in reconstructed CT images at a substantially reduced dose compared to phosphor-coated readouts. The use of CMOS technology allows for small pixels (30 mum), fast readout speeds (8 fps for a 3200 times 3200 pixel array), and future design flexibility due to the use of well-developed fabrication processes.