Abstract
Presence of a signal lag is a bottle neck of performance for many non-crystalline materials, considered for dynamic radiation sensing. Due to inadequate lag-related temporal performance, polycrystalline layers of CdZnTe, PbI2, HgI2 and PbO are not practically utilized, despite their superior X-ray sensitivity and low production cost (even for large area detectors). In the current manuscript, we show that a technological step to replace nonhomogeneous disorder in polycrystalline PbO with homogeneous amorphous PbO structure suppresses signal lag and improves time response to X-ray irradiation. In addition, the newly developed amorphous lead oxide (a-PbO) possesses superior X-ray sensitivity in terms of electron-hole pair creation energy {W}_{pm } in comparison with amorphous selenium – currently the only photoconductor used as an X-ray-to-charge transducer in the state-of-the-art direct conversion X-ray medical imaging systems. The proposed advances of the deposition process are low cost, easy to implement and with certain customization might potentially be applied to other materials, thus paving the way to their wide-range commercial use.
Highlights
Presence of a signal lag is a bottle neck of performance for many non-crystalline materials, considered for dynamic radiation sensing
Other polycrystalline high-Z materials that have been considered for applications as radiation detectors are all suffering from the same problem, i.e. signal lag
In terms of signal lag, the only exemption in the series of disordered materials considered for application in radiation sensing, is amorphous selenium (a-Se), where technological advances allowed suppression of signal lag to a level that this material became a practical solution for advanced direct conversion X-ray medical imaging detectors
Summary
Presence of a signal lag is a bottle neck of performance for many non-crystalline materials, considered for dynamic radiation sensing. While the properties of poly-CdTe films are fit for optical photon harvesting in high efficiency solar cells[11,12,13,14], there are reported to be challenges for applications in X-ray medical imaging Both poly-CdTe and poly-CdZnTe suffer from a residual signal after exposure termination, called signal lag[15,16,17,18]. In terms of signal lag, the only exemption in the series of disordered materials considered for application in radiation sensing, is amorphous selenium (a-Se), where technological advances allowed suppression of signal lag to a level that this material became a practical solution for advanced direct conversion X-ray medical imaging detectors. The measurements performed at various exposures and at an extended range of electric fields suggests the suitability of a-PbO for real time imaging at 30 frames per second (fps)
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