Imaging performance of mercuric iodide polycrystalline films

Mercuric iodide (HgI2) polycrystalline films have great potential as direct-conversion X-ray detectors for digital X-ray imaging. We have optimized a sublimation-based film growth process to create uniform films up to 6.5 x 6.5 cm(2) with very small (< 25 mum) grain sizes on the readout side of the film. The growth techniques used can be easily extended to produce much larger film areas (> 25 cm x 25 cm). Films grown on glass substrates uniformly coated with indium tin oxide (ITO) show low dark current and high sensitivity at low bias voltages: dark current of about 0.5 nA/cm(2) and corresponding X-ray response of about 20 muC/R cm(2) (bias 0.1 V/mum, X-ray tube settings 10 mA and 70 kVp, 2-mm Al filter). Additionally, films grown on patterned ITO on glass substrates showed a similar performance for pixel sizes of 10.2 to 4 mm(2). The imaging performance results of a film grown directly on a 6.5 x 6.5 (cm(2)) thin-film transistor array with 127 mum x 127 mum pixels are presented.