Imaging performance of mercuric iodide polycrystalline films

Mercuric iodide (HgI/sub 2/) 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 /spl times/ 6.5 cm/sup 2/ with very small (<25 /spl mu/m) 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 /spl times/ 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/sup 2/ and corresponding X-ray response of about 20 /spl mu/C/R cm/sup 2/ (bias 0.1 V//spl mu/m, 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/sup 2/. The imaging performance results of a film grown directly on a 6.5 /spl times/ 6.5 (cm/sup 2/) thin-film transistor array with 127 /spl mu/m /spl times/ 127 /spl mu/m pixels are presented.