报告题目：“Amorphous lead oxide (a-PbO) for application in direct conversion X-ray detectors: use of polymorphism to suppress signal lag”
报 告 人： Prof. Alla Reznik
时 间： 2018年4月20日 上午 10:00-11:00
地 点： 东校园微电子学院大楼102讲学厅
主 持 人： 王凯 教授
Semiconductor-based direct-conversion X-ray detectors have been actively sought for a wide range of xray applications in the fields of domestic security and medical imaging. Lead Oxide (PbO) is one of the most promising high Z (atomic number) candidates for this purpose due to high X-ray stopping power, high theoretical X-ray-to-charge conversion gain and proven technological compatibility with a-Si electronics required for a large detector area coating. Polycrystalline modification of lead oxide (polyPbO) has a long and successful history of applications in optoelectronics where it was employed as a phototarget in Plumbicons – the most extensively used pick-up tubes for broadcasting. The success of Plumbicons triggered great interest in utilizing PbO layers for X-ray medical imaging detectors. Unfortunately, poly-PbO photoconductive layers were reported to be challenging for applications in realtime X-ray medical imaging due to the presence of a residual signal after exposure termination, called signal lag. Signal lag leads to inadequate temporal characteristics and therefore it is a bottle neck of performance for many non-crystalline materials, considered for dynamic radiation sensing. Here we analyze causes of signal lag in poly-PbO layers and 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. Our study suggests a way to make detector-grade PbO layers free of lag. 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.
Dr. Alla Reznik is a Canada Research Chair in Physics of Molecular Imaging and Professor in the Physics Department, Faculty of Science and Environmental Studies. She is also affiliated as a Senior Scientist in the Thunder Bay Regional Health Research Institute (TBRHRI). Dr. Reznik has completed her PhD in solid-state physics at the Technion- Israel Institute of Technology. After several years as a Senior Physicist at the GE Medical Systems she decided to return to academia and accepted a Research Associate position at the University of Toronto, Canada. In 2008 she was appointed a Canada Research Chair in Physics of Molecular Imaging and in 2013 re-appointed as a Canada Research Chair in Physics of Medical Imaging. She is a specialist in photoconductive materials and technologies for radiation medical imaging. The focus of her work is on solid-state technology for organ-specific Positron Emission Tomography (PET). The goal is an improvement in resolution and sensitivity over commercially available PET imagers. Another focus of her work is on advanced low-dose direct conversion x-ray imaging detectors based on novel x-ray-to-charge transducers. Reznik group’s PET research has led to the launch of Radialis Medical – the first joint Lakehead – TBRHRI spin-off company, which will produce a commercial version of the technology for breast cancer detection.