Fabrication and characterization of X-ray array detectors based on polycrystalline PbI₂ thick films

Polycrystalline PbI₂ thick films were grown by using close spaced vapor deposition method on glass substrate with a conducting indium–tin-oxide coating. The morphology shows a uniquely oriented film structure with hexagonal platelets accurately being upright on substrate surface. An array detector with 12 pixels was fabricated based on this structure of the thick film. It is shown that the dark current is lower than 3 nA at bias voltage below 500 V, and the dark resistivity is as high as 10¹¹ Ω cm. A mapping of dark current density of the sensitive area of the array detector exhibits a better uniformity in the central area than the fringe area. A quick photocurrent response to X-ray excitation was obtained. The photoresponse rise time about 250 μs was obtained from the detectors and the photocurrent decays in a few seconds. The values of photocurrent are higher about two orders of magnitude than the values of dark current. The distribution of photocurrent is more uniform than that of dark current in the sensitive area of the detector.