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Girolami M, Matteocci F, Pettinato S, Serpente V, Bolli E, Paci B, Generosi A, Salvatori S, Di Carlo A, Trucchi DM. Metal-Halide Perovskite Submicrometer-Thick Films for Ultra-Stable Self-Powered Direct X-Ray Detectors. NANO-MICRO LETTERS 2024; 16:182. [PMID: 38668830 PMCID: PMC11052987 DOI: 10.1007/s40820-024-01393-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Accepted: 03/08/2024] [Indexed: 04/29/2024]
Abstract
Metal-halide perovskites are revolutionizing the world of X-ray detectors, due to the development of sensitive, fast, and cost-effective devices. Self-powered operation, ensuring portability and low power consumption, has also been recently demonstrated in both bulk materials and thin films. However, the signal stability and repeatability under continuous X-ray exposure has only been tested up to a few hours, often reporting degradation of the detection performance. Here it is shown that self-powered direct X-ray detectors, fabricated starting from a FAPbBr3 submicrometer-thick film deposition onto a mesoporous TiO2 scaffold, can withstand a 26-day uninterrupted X-ray exposure with negligible signal loss, demonstrating ultra-high operational stability and excellent repeatability. No structural modification is observed after irradiation with a total ionizing dose of almost 200 Gy, revealing an unexpectedly high radiation hardness for a metal-halide perovskite thin film. In addition, trap-assisted photoconductive gain enabled the device to achieve a record bulk sensitivity of 7.28 C Gy-1 cm-3 at 0 V, an unprecedented value in the field of thin-film-based photoconductors and photodiodes for "hard" X-rays. Finally, prototypal validation under the X-ray beam produced by a medical linear accelerator for cancer treatment is also introduced.
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Affiliation(s)
- Marco Girolami
- CNR-ISM, Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia, Sede Secondaria di Montelibretti, DiaTHEMA Lab, Strada Provinciale 35D, 9, 00010, Montelibretti, Rome, Italy.
| | - Fabio Matteocci
- CHOSE - Centre for Hybrid and Organic Solar Energy, Department of Electronic Engineering, University of Rome ''Tor Vergata'', Via del Politecnico 1, 00133, Rome, Italy
| | - Sara Pettinato
- CNR-ISM, Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia, Sede Secondaria di Montelibretti, DiaTHEMA Lab, Strada Provinciale 35D, 9, 00010, Montelibretti, Rome, Italy
- Faculty of Engineering, Università degli Studi Niccolò Cusano, Via don Carlo Gnocchi 3, 00166, Rome, Italy
| | - Valerio Serpente
- CNR-ISM, Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia, Sede Secondaria di Montelibretti, DiaTHEMA Lab, Strada Provinciale 35D, 9, 00010, Montelibretti, Rome, Italy
| | - Eleonora Bolli
- CNR-ISM, Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia, Sede Secondaria di Montelibretti, DiaTHEMA Lab, Strada Provinciale 35D, 9, 00010, Montelibretti, Rome, Italy
| | - Barbara Paci
- SpecXLab, CNR-ISM, Consiglio Nazionale Delle Ricerche, Istituto di Struttura Della Materia, Area della Ricerca di Tor Vergata, Via del Fosso del Cavaliere 100, 00133, Rome, Italy
| | - Amanda Generosi
- SpecXLab, CNR-ISM, Consiglio Nazionale Delle Ricerche, Istituto di Struttura Della Materia, Area della Ricerca di Tor Vergata, Via del Fosso del Cavaliere 100, 00133, Rome, Italy
| | - Stefano Salvatori
- CNR-ISM, Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia, Sede Secondaria di Montelibretti, DiaTHEMA Lab, Strada Provinciale 35D, 9, 00010, Montelibretti, Rome, Italy
- Faculty of Engineering, Università degli Studi Niccolò Cusano, Via don Carlo Gnocchi 3, 00166, Rome, Italy
| | - Aldo Di Carlo
- CHOSE - Centre for Hybrid and Organic Solar Energy, Department of Electronic Engineering, University of Rome ''Tor Vergata'', Via del Politecnico 1, 00133, Rome, Italy
- SpecXLab, CNR-ISM, Consiglio Nazionale Delle Ricerche, Istituto di Struttura Della Materia, Area della Ricerca di Tor Vergata, Via del Fosso del Cavaliere 100, 00133, Rome, Italy
| | - Daniele M Trucchi
- CNR-ISM, Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia, Sede Secondaria di Montelibretti, DiaTHEMA Lab, Strada Provinciale 35D, 9, 00010, Montelibretti, Rome, Italy
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2
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Dudipala KR, Le TH, Nie W, Hoye RLZ. Halide Perovskites and Their Derivatives for Efficient, High-Resolution Direct Radiation Detection: Design Strategies and Applications. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2304523. [PMID: 37726105 DOI: 10.1002/adma.202304523] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Revised: 09/03/2023] [Indexed: 09/21/2023]
Abstract
The past decade has witnessed a rapid rise in the performance of optoelectronic devices based on lead-halide perovskites (LHPs). The large mobility-lifetime products and defect tolerance of these materials, essential for optoelectronics, also make them well-suited for radiation detectors, especially given the heavy elements present, which is essential for strong X-ray and γ-ray attenuation. Over the past decade, LHP thick films, wafers, and single crystals have given rise to direct radiation detectors that have outperformed incumbent technologies in terms of sensitivity (reported values up to 3.5 × 106 µC Gyair -1 cm-2 ), limit of detection (directly measured values down to 1.5 nGyair s-1 ), along with competitive energy and imaging resolution at room temperature. At the same time, lead-free perovskite-inspired materials (e.g., methylammonium bismuth iodide), which have underperformed in solar cells, have recently matched and, in some areas (e.g., in polarization stability), surpassed the performance of LHP detectors. These advances open up opportunities to achieve devices for safer medical imaging, as well as more effective non-invasive analysis for security, nuclear safety, or product inspection applications. Herein, the principles behind the rapid rises in performance of LHP and perovskite-inspired material detectors, and how their properties and performance link with critical applications in non-invasive diagnostics are discussed. The key strategies to engineer the performance of these materials, and the important challenges to overcome to commercialize these new technologies are also discussed.
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Affiliation(s)
| | - Thanh-Hai Le
- Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Wanyi Nie
- Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Robert L Z Hoye
- Inorganic Chemistry Laboratory, University of Oxford, Oxford, OX1 3QR, UK
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3
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Song Z, Du X, He X, Wang H, Liu Z, Wu H, Luo H, Jin L, Xu L, Zheng Z, Niu G, Tang J. Rheological engineering of perovskite suspension toward high-resolution X-ray flat-panel detector. Nat Commun 2023; 14:6865. [PMID: 37891158 PMCID: PMC10611698 DOI: 10.1038/s41467-023-42616-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 10/17/2023] [Indexed: 10/29/2023] Open
Abstract
Solution-processed polycrystalline perovskite film is promising for the next generation X-ray imaging. However, the spatial resolution of current perovskite X-ray panel detectors is far lower than the theoretical limit. Herein we find that the pixel level non-uniformity, also known as fixed pattern noise, is the chief culprit affecting the signal-to-noise ratio and reducing the resolution of perovskite detectors. We report a synergistic strategy of rheological engineering the perovskite suspensions to achieve X-ray flat panel detectors with pixel-level high uniformity and near-to-limit spatial resolution. Our approach includes the addition of methylammonium iodide and polyacrylonitrile to the perovskite suspension, to synergistically enhance the flowability and particle stability of the oversaturated solution. The obtained suspension perfectly suits for the blade-coating process, avoiding the uneven distribution of solutes and particles within perovskite films. The assembled perovskite panel detector exhibits greatly improved fixed pattern noise value (1.39%), high sensitivity (2.24 × 104 μC Gyair-1 cm-2), low detection limit (28.57 nGyair·s-1) as well as good working stability, close to the performance of single crystal detectors. Moreover, the detector achieves a near-to-limit resolution of 0.51 lp/pix.
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Grants
- the Major State Basic Research Development Program of China,2021YFB3201000,the National Nature Science Foundation of China,62134003,62074066 and 12050005,the Fund for Innovative Research Groups of the Natural Science Foundation of Hubei Province,2021CFA036, 2020CFA034,the Shenzhen Basic Research Program,JCYJ20200109115212546,the Fundamental Research Funds for the Central Universities HUST,2020JYCXJJ073, YCJJ202203001,the Innovation Foundation of Innovation Institute, Huazhong university of science and technology,5003187018
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Affiliation(s)
- Zihao Song
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China
| | - Xinyuan Du
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China
| | - Xin He
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China
| | - Hanqi Wang
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China
| | - Zhiqiang Liu
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China
| | - Haodi Wu
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China
| | - Hongde Luo
- iRay Technology Company Limited, 201206, Shanghai, China
| | - Libo Jin
- iRay Technology Company Limited, 201206, Shanghai, China
| | - Ling Xu
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China
| | - Zhiping Zheng
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China
| | - Guangda Niu
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China.
- Ezhou Industrial Technology Research Institute of Huazhong University of Science and Technology, 436060, Ezhou, China.
| | - Jiang Tang
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China
- Ezhou Industrial Technology Research Institute of Huazhong University of Science and Technology, 436060, Ezhou, China
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Xu X, Wang F, Xu W, Lu H, Lv L, Sha H, Jiang X, Wu S, Wang S. Wide-Bandgap Rare-Earth Iodate Single Crystals for Superior X-Ray Detection and Imaging. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2206833. [PMID: 36950744 DOI: 10.1002/advs.202206833] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 02/17/2023] [Indexed: 05/18/2023]
Abstract
Semiconductor-based X-ray detectors with low detectable thresholds become critical in medical radiography applications. However, their performance is generally limited by intrinsic defects or unresolved issues of materials, and developing a novel scintillation semiconductor for low-dose X-ray detection is a highly urgent objective. Herein, a high-quality rare-earth iodate Tm(IO3 )3 single crystal grown through low-cost solution processing is reported with a wide bandgap of 4.1 eV and a large atomic number of 53.2. The roles of IO and TmO groups for charge transport in the Tm(IO3 )3 are revealed with the structural difference between the [101] and [ 1 ¯ 01 ] $[{\bar{1}}01]$ crystal orientations. Based on anisotropic responses of material properties and detection performances, it is found that the [ 1 ¯ 01 ${\bar{1}}01$ ] orientation, the path with fewer IO groups, achieves a high resistivity of 1.02 × 1011 Ω cm. Consequently, a single-crystal detector exhibits a low dark current and small baseline drifting due to the wide bandgap, high resistivity and less ion migration of Tm(IO3 )3 , resulting in a low detection limit of 85.2 nGyair s-1 . An excellent X-ray imaging performance with a high sensitivity of 4406.6 µC Gyair -1 cm-2 is also shown in the Tm(IO3 )3 device. These findings provide a new material design perspective for high-performance X-ray imaging applications.
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Affiliation(s)
- Xieming Xu
- Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Fang Wang
- Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
| | - Weiwei Xu
- Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
| | - Hao Lu
- Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lingfei Lv
- Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hongyuan Sha
- Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaoming Jiang
- Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
| | - Shaofan Wu
- Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
| | - Shuaihua Wang
- Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
- Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian, 350002, China
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5
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Shen L, Antonuk LE, El-Mohri Y, Zhao Q. Minimization of image lag in polycrystalline mercuric iodide converters through incorporation of Frisch grid structures for digital breast tomosynthesis. Phys Med Biol 2023; 68. [PMID: 36635788 DOI: 10.1088/1361-6560/aca952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 12/06/2022] [Indexed: 01/14/2023]
Abstract
Objective. Polycrystalline mercuric iodide photoconductive converters fabricated using particle-in-binder techniques (PIB HgI2) provide significantly more detected charge per x-ray interaction than from a-Se and CsI:Tl converters commonly used with active matrix flat-panel imagers (AMFPIs). This enhanced sensitivity makes PIB HgI2an interesting candidate for applications involving low x-ray exposures-since the relatively high levels of additive electronic noise exhibited by AMFPIs incorporating a-Se and CsI:Tl reduce detective quantum efficiency (DQE) performance under such conditions. A theoretical study is reported on an approach for addressing a major challenge impeding practical use of PIB HgI2converters-the high lag exhibited by the material (over 10%) which would lead to undesirable image artifacts in applications involving acquisition of consecutive images such as digital breast tomosynthesis.Approach. Charge transport modeling accounting for the trapping and release of holes (thought to be the primary contributor to lag) was used to examine signal properties, including lag, of pillar-supported Frisch grids embedded in the photoconductor for 100μm pitch AMFPI pixels. Performance was examined as a function of electrode voltage, grid pitch (center-to-center distance between neighboring grid wires) and the ratio of grid wire width to grid pitch.Main results. Optimum grid designs maximizing suppression of signal generated by hole transport, without significantly affecting the total signal due to electron and hole transport, were identified and MTF was determined. For the most favorable designs, additional modeling was used to determine DQE. The results indicate that, through judicious choice of grid design and operational conditions, first frame lag can be significantly reduced to below 1%-less than the low levels exhibited by a-Se. DQE performance is shown to be largely maintained as exposure decreases-which should help to maintain good image quality.Significance. Substantial reduction of lag in PIB HgI2converters via incorporation of Frisch grids has been demonstrated through modeling.
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Affiliation(s)
- Liuxing Shen
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Larry E Antonuk
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Youcef El-Mohri
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Qihua Zhao
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
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6
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Dong K, Zhou H, Shao W, Gao Z, Yao F, Xiao M, Li J, Liu Y, Wang S, Zhou S, Cui H, Qin M, Lu X, Tao C, Ke W, Fang G. Perovskite-like Silver Halide Single-Crystal Microbelt Enables Ultrasensitive Flexible X-ray Detectors. ACS NANO 2023; 17:1495-1504. [PMID: 36617722 DOI: 10.1021/acsnano.2c10318] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Lead halide perovskite single crystals have attracted wide interest in the field of X-ray detection due to their excellent photophysical properties. However, their inherent toxicity and high thickness restrict their applications in flexible devices. In this paper, designing a micronanometer-scale X-ray detector based on all-inorganic lead-free CsAg2I3 (CAI) single crystal microbelts (MBs) has addressed the above issues. These CAI single crystal MBs can be synthesized on various substrates with high crystal quality and excellent stability. Based on their excellent characteristics of the CAI MBs, we fabricate single CAI MB devices with an Au/CAI/Au structure, which shows not only good ultraviolet photoresponse characteristics, but also excellent X-ray detection performance. The optimized CAI photodetectors exhibit a responsivity of 23.59 mA/W, a high detectivity of 1010 Jones, and a fast response speed. For X-ray detection performance, a sensitivity of up to 515.49 μC Gyair-1 cm-2 and a detection limit of as low as 14.65 μGyair s-1 are achieved with outstanding operation stability and excellent long-term stability. Furthermore, our devices also showed excellent applicability for X-ray imaging, which is promising for their use in X-ray detection and imaging. Finally, flexible X-ray detectors are fabricated by using thin CAI single-crystal MBs and demonstrate good flexibility under different bending radii and bending cycles. Our work shows the potential for developing highly sensitive flexible integrated micro/nano optoelectronic devices by using lead-free perovskite analogue single crystals.
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Affiliation(s)
- Kailian Dong
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
- Shenzhen Institute, Wuhan University, Shenzhen, Guangdong 518055, PR China
| | - Hai Zhou
- International School of Microelectronics, Dongguan University of Technology, Dongguan, Guangdong 523808, PR China
| | - Wenlong Shao
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Zheng Gao
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Fang Yao
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Meng Xiao
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Jiashuai Li
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Yongjie Liu
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Shuxin Wang
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Shun Zhou
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Hongsen Cui
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Minchao Qin
- Department of Physics, The Chinese University of Hong Kong, 999077 Hong Kong SAR, China
| | - Xinhui Lu
- Department of Physics, The Chinese University of Hong Kong, 999077 Hong Kong SAR, China
| | - Chen Tao
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Weijun Ke
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
| | - Guojia Fang
- Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
- Shenzhen Institute, Wuhan University, Shenzhen, Guangdong 518055, PR China
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7
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Wu Y, Feng J, Yang Z, Liu Y, Liu S(F. Halide Perovskite: A Promising Candidate for Next-Generation X-Ray Detectors. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 10:e2205536. [PMID: 36453564 PMCID: PMC9811474 DOI: 10.1002/advs.202205536] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 10/30/2022] [Indexed: 05/31/2023]
Abstract
In the past decade, metal halide perovskite (HP) has become a superstar semiconductor material due to its great application potential in the photovoltaic and photoelectric fields. In fact, HP initially attracted worldwide attention because of its excellent photovoltaic efficiency. However, HP and its derivatives also show great promise in X-ray detection due to their strong X-ray absorption, high bulk resistivity, suitable optical bandgap, and compatibility with integrated circuits. In this review, the basic working principles and modes of both the direct-type and the indirect-type X-ray detectors are first summarized before discussing the applicability of HP for these two types of detection based on the pros and cons of different perovskites. Furthermore, the authors expand their view to different preparation methods developed for HP including single crystals and polycrystalline materials. Upon systematically analyzing their potential for X-ray detection and photoelectronic characteristics on the basis of different structures and dimensions (0D, 2D, and 3D), recent progress of HPs (mainly polycrystalline) applied to flexible X-ray detection are reviewed, and their practicability and feasibility are discussed. Finally, by reviewing the current research on HP-based X-ray detection, the challenges in this field are identified, and the main directions and prospects of future research are suggested.
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Affiliation(s)
- Ya Wu
- College of Chemistry and Chemical EngineeringXi'an Shiyou UniversityXi'an710065China
- Key Laboratory of Applied Surface and Colloid ChemistryNational Ministry of EducationShaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal UniversityXi'an710119China
| | - Jiangshan Feng
- Key Laboratory of Applied Surface and Colloid ChemistryNational Ministry of EducationShaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal UniversityXi'an710119China
| | - Zhou Yang
- Key Laboratory of Applied Surface and Colloid ChemistryNational Ministry of EducationShaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal UniversityXi'an710119China
| | - Yucheng Liu
- Key Laboratory of Applied Surface and Colloid ChemistryNational Ministry of EducationShaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal UniversityXi'an710119China
| | - Shengzhong (Frank) Liu
- Key Laboratory of Applied Surface and Colloid ChemistryNational Ministry of EducationShaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal UniversityXi'an710119China
- State Key Laboratory of CatalysisDalian National Laboratory for Clean EnergyDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian116023China
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8
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Shen L, Antonuk LE, El-Mohri Y, Liang AK, Zhao Q, Jiang H. Theoretical investigation of the signal performance of HgI 2x-ray converters incorporating a Frisch grid structure at mammographic energies. Phys Med Biol 2021; 66. [PMID: 34252890 DOI: 10.1088/1361-6560/ac1365] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 07/12/2021] [Indexed: 11/12/2022]
Abstract
Active matrix, flat-panel imagers (AMFPIs) suffer from decreased detective quantum efficiency under conditions of low dose per image frame (such as for digital breast tomosynthesis, fluoroscopy and cone-beam CT) due to low signal compared to the additive electronic noise. One way to address this challenge is to introduce a high-gain x-ray converter called particle-in-binder mercuric iodide (PIB HgI2) which exhibits 3-10 times higher x-ray sensitivity compared to that of a-Se and CsI:Tl converters employed in commercial AMFPI systems. However, a remaining challenge for practical implementation of PIB HgI2is the high level of image lag, which is believed to largely originate from the trapping of holes. Towards addressing this challenge, this paper reports a theoretical investigation of the use of a Frisch grid structure embedded in the converter to suppress hole signal-which would be expected to reduce image lag. The grid acts as a third electrode sandwiched between a continuous top electrode and pixelated bottom electrodes having a 100μm pitch. Signal properties of such a detector are investigated as a function of VDR (the ratio of the voltage difference between the electrodes in the region below the grid to that above the grid), grid pitch (the center-to-center distance between two neighboring grid wires) andRGRID(the ratio of grid wire width to grid pitch) for mammographic x-ray energies. The results show that smaller grid pitch suppresses hole signal to a higher degree (up to ∼96%) while a larger gap between grid wires and higher VDR provide minimally impeded electron transport. Examination of the tradeoff between maximizing electron signal and minimizing hole signal indicates that a grid design having a grid pitch of 20μm withRGRIDof 50% and 65% provides hole signal suppression of ∼93% and ∼95% for VDR of 1 and 3, respectively.
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Affiliation(s)
- Liuxing Shen
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Larry E Antonuk
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Youcef El-Mohri
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Albert K Liang
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Qihua Zhao
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Hao Jiang
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, United States of America
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Koniczek M, Antonuk LE, El‐Mohri Y, Liang AK, Zhao Q. Empirical noise performance of prototype active pixel arrays employing polycrystalline silicon thin‐film transistors. Med Phys 2020; 47:3972-3983. [DOI: 10.1002/mp.14321] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 04/26/2020] [Accepted: 05/26/2020] [Indexed: 12/11/2022] Open
Affiliation(s)
- Martin Koniczek
- Department of Radiation Oncology University of Michigan Ann Arbor MI 48109 USA
| | - Larry E. Antonuk
- Department of Radiation Oncology University of Michigan Ann Arbor MI 48109 USA
| | - Youcef El‐Mohri
- Department of Radiation Oncology University of Michigan Ann Arbor MI 48109 USA
| | - Albert K. Liang
- Department of Radiation Oncology University of Michigan Ann Arbor MI 48109 USA
| | - Qihua Zhao
- Department of Radiation Oncology University of Michigan Ann Arbor MI 48109 USA
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Koniczek M, Antonuk LE, El-Mohri Y, Liang AK, Zhao Q. Theoretical investigation of the noise performance of active pixel imaging arrays based on polycrystalline silicon thin film transistors. Med Phys 2017; 44:3491-3503. [PMID: 28376261 DOI: 10.1002/mp.12257] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 02/02/2017] [Accepted: 03/21/2017] [Indexed: 02/01/2023] Open
Abstract
PURPOSE Active matrix flat-panel imagers, which typically incorporate a pixelated array with one a-Si:H thin-film transistor (TFT) per pixel, have become ubiquitous by virtue of many advantages, including large monolithic construction, radiation tolerance, and high DQE. However, at low exposures such as those encountered in fluoroscopy, digital breast tomosynthesis and breast computed tomography, DQE is degraded due to the modest average signal generated per interacting x-ray relative to electronic additive noise levels of ~1000 e, or greater. A promising strategy for overcoming this limitation is to introduce an amplifier into each pixel, referred to as the active pixel (AP) concept. Such circuits provide in-pixel amplification prior to readout as well as facilitate correlated multiple sampling, enhancing signal-to-noise and restoring DQE at low exposures. In this study, a methodology for theoretically investigating the signal and noise performance of imaging array designs is introduced and applied to the case of AP circuits based on low-temperature polycrystalline silicon (poly-Si), a semiconductor suited to manufacture of large area, radiation tolerant arrays. METHODS Computer simulations employing an analog circuit simulator and performed in the temporal domain were used to investigate signal characteristics and major sources of electronic additive noise for various pixel amplifier designs. The noise sources include photodiode shot noise and resistor thermal noise, as well as TFT thermal and flicker noise. TFT signal behavior and flicker noise were parameterized from fits to measurements performed on individual poly-Si test TFTs. The performance of three single-stage and three two-stage pixel amplifier designs were investigated under conditions relevant to fluoroscopy. The study assumes a 20 × 20 cm2 , 150 μm pitch array operated at 30 fps and coupled to a CsI:Tl x-ray converter. Noise simulations were performed as a function of operating conditions, including sampling mode, of the designs. The total electronic additive noise included noise contributions from each circuit component. RESULTS The total noise results were found to exhibit a strong dependence on circuit design and operating conditions, with TFT flicker noise generally found to be the dominant noise contributor. For the single-stage designs, significantly increasing the size of the source-follower TFT substantially reduced flicker noise - with the lowest total noise found to be ~574 e [rms]. For the two-stage designs, in addition to tuning TFT sizes and introducing a low-pass filter, replacing a p-type TFT with a resistor (under the assumption in the study that resistors make no flicker noise contribution) resulted in significant noise reduction - with the lowest total noise found to be ~336 e [rms]. CONCLUSIONS A methodology based on circuit simulations which facilitates comprehensive explorations of signal and noise characteristics has been developed and applied to the case of poly-Si AP arrays. The encouraging results suggest that the electronic additive noise of such devices can be substantially reduced through judicious circuit design, signal amplification, and multiple sampling. This methodology could be extended to explore the noise performance of arrays employing other pixel circuitry such as that for photon counting as well as other semiconductor materials such as a-Si:H and a-IGZO.
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Affiliation(s)
- Martin Koniczek
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Larry E Antonuk
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Youcef El-Mohri
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Albert K Liang
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Qihua Zhao
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 48109, USA
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11
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Photoconductors for X-Ray Image Detectors. SPRINGER HANDBOOK OF ELECTRONIC AND PHOTONIC MATERIALS 2017. [DOI: 10.1007/978-3-319-48933-9_45] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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12
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Semeniuk O, Juska G, Oelerich JO, Wiemer M, Baranovskii SD, Reznik A. Charge transport mechanism in lead oxide revealed by CELIV technique. Sci Rep 2016; 6:33359. [PMID: 27628537 PMCID: PMC5024125 DOI: 10.1038/srep33359] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 08/25/2016] [Indexed: 01/19/2023] Open
Abstract
Although polycrystalline lead oxide (PbO) belongs to the most promising photoconductors for optoelectronic and large area detectors applications, the charge transport mechanism in this material still remains unclear. Combining the conventional time-of-flight and the photo-generated charge extraction by linear increasing voltage (photo-CELIV) techniques, we investigate the transport of holes which are shown to be the faster carriers in poly-PbO. Experimentally measured temperature and electric field dependences of the hole mobility suggest a highly dispersive transport. In order to analyze the transport features quantitatively, the theory of the photo-CELIV is extended to account for the dispersive nature of charge transport. While in other materials with dispersive transport the amount of dispersion usually depends on temperature, this is not the case in poly-PbO, which evidences that dispersive transport is caused by the spatial inhomogeneity of the material and not by the energy disorder.
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Affiliation(s)
- O Semeniuk
- Chemistry and Material Science Program, Lakehead University, 955 Oliver Road, Thunder Bay, ON, P7B 5E1, Canada
| | - G Juska
- Department of Solid State Electronics, Vilnius University, Saulėtekio 9 III k., 10222 Vilnius, Lithuania
| | - J-O Oelerich
- Faculty of Physics, Philipps University Marburg, Renthof 6, 35032 Marburg, Germany
| | - M Wiemer
- Faculty of Physics, Philipps University Marburg, Renthof 6, 35032 Marburg, Germany
| | - S D Baranovskii
- Faculty of Physics, Philipps University Marburg, Renthof 6, 35032 Marburg, Germany
| | - A Reznik
- Department of Physics, Lakehead University, 955 Oliver Road, Thunder Bay, ON, P7B 5E1, Canada.,Advanced detection devices department, Thunder Bay Regional Research Institute, 290 Munro Street, Thunder Bay, ON, P7A 7T1, Canada
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Park JC, Jeon PJ, Kim JS, Im S. Small-dose-sensitive X-ray image pixel with HgI2 photoconductor and amorphous oxide thin-film transistor. Adv Healthc Mater 2015; 4:51-7. [PMID: 24753443 DOI: 10.1002/adhm.201400077] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 03/15/2014] [Indexed: 11/09/2022]
Abstract
A new X-ray image sensor is demonstrated with an oxide thin-film transistor backplane and HgI2 sensing material. It displays outstanding image quality under a low X-ray exposure and a low electric field. It is promising as a state-of-the-art device to realize highly resolved images at a low X-ray dose for a variety of medical X-ray imaging applications.
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Affiliation(s)
- Jae Chul Park
- Institute of Physics and Applied Physics; Yonsei University; 262 Seongsanno Seodaemun-gu, Seoul 120-749 Korea
| | - Pyo Jin Jeon
- Institute of Physics and Applied Physics; Yonsei University; 262 Seongsanno Seodaemun-gu, Seoul 120-749 Korea
| | - Jin Sung Kim
- Institute of Physics and Applied Physics; Yonsei University; 262 Seongsanno Seodaemun-gu, Seoul 120-749 Korea
| | - Seongil Im
- Institute of Physics and Applied Physics; Yonsei University; 262 Seongsanno Seodaemun-gu, Seoul 120-749 Korea
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14
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Jiang H, Zhao Q, Antonuk LE, El-Mohri Y, Gupta T. Development of active matrix flat panel imagers incorporating thin layers of polycrystalline HgI(2) for mammographic x-ray imaging. Phys Med Biol 2013; 58:703-14. [PMID: 23318606 DOI: 10.1088/0031-9155/58/3/703] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Active matrix flat-panel imagers (AMFPIs) offer many advantages and have become ubiquitous across a wide variety of medical x-ray imaging applications. However, for mammography, the imaging performance of conventional AMFPIs incorporating CsI:Tl scintillators or a-Se photoconductors is limited by their relatively modest signal-to-noise ratio (SNR), particularly at low x-ray exposures or high spatial resolution. One strategy for overcoming this limitation involves the use of a high gain photoconductor such as mercuric iodide (HgI(2)) which has the potential to improve the SNR by virtue of its low effective work function (W(EFF)). In this study, the performance of direct-detection AMFPI prototypes employing relatively thin layers of polycrystalline HgI(2) operated under mammographic irradiation conditions over a range of 0.5 to 16.0 mR is presented. High x-ray sensitivity (corresponding to W(EFF) values of ∼19 eV), low dark current (<0.1 pA mm(-2)) and good spatial resolution, largely limited by the size of the pixel pitch, were observed. For one prototype, a detective quantum efficiency of ∼70% was observed at an x-ray exposure of ∼0.5 mR at 26 kVp.
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Affiliation(s)
- Hao Jiang
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA
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Abstract
PURPOSE The authors examined the effect of detector lag on the noise power spectrum (NPS) of CT images reconstructed with filtered backprojection (FBP). METHODS The authors derived an analytical expression of the NPS with detector lag, and then verified it using computer simulations with parallel beam and fan beam geometries. The dependence of the NPS on the amount of lag, location within the scanned field of view (FOV), and the number of views used in the reconstruction (samples per rotation) was investigated using constant and view dependent noise in the raw data. RESULTS Detector lag introduces noise correlation in the azimuthal direction. The effect on the NPS is a frequency dependent reduction in amplitude. In small regions of the image, the effect is primarily in the frequencies corresponding to the azimuthal direction. The noise blurring and NPS filtering increases with increasing radial distance, and therefore regions at larger radial distances have lower noise power. With the same detector lag response function, the amount of noise correlation and NPS filtering decreases with increasing number of views. CONCLUSIONS The shape of the NPS depends on the detector lag coefficients, location of the region, and the number of views used in the reconstruction. In general, the noise correlation caused by detector lag decreased the amplitude of the NPS.
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Affiliation(s)
- Jongduk Baek
- Department of Radiology, Stanford University, Stanford, California 94305, USA.
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16
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Kasap S, Frey JB, Belev G, Tousignant O, Mani H, Greenspan J, Laperriere L, Bubon O, Reznik A, DeCrescenzo G, Karim KS, Rowlands JA. Amorphous and polycrystalline photoconductors for direct conversion flat panel x-ray image sensors. SENSORS 2011; 11:5112-57. [PMID: 22163893 PMCID: PMC3231396 DOI: 10.3390/s110505112] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 04/25/2011] [Accepted: 05/04/2011] [Indexed: 11/29/2022]
Abstract
In the last ten to fifteen years there has been much research in using amorphous and polycrystalline semiconductors as x-ray photoconductors in various x-ray image sensor applications, most notably in flat panel x-ray imagers (FPXIs). We first outline the essential requirements for an ideal large area photoconductor for use in a FPXI, and discuss how some of the current amorphous and polycrystalline semiconductors fulfill these requirements. At present, only stabilized amorphous selenium (doped and alloyed a-Se) has been commercialized, and FPXIs based on a-Se are particularly suitable for mammography, operating at the ideal limit of high detective quantum efficiency (DQE). Further, these FPXIs can also be used in real-time, and have already been used in such applications as tomosynthesis. We discuss some of the important attributes of amorphous and polycrystalline x-ray photoconductors such as their large area deposition ability, charge collection efficiency, x-ray sensitivity, DQE, modulation transfer function (MTF) and the importance of the dark current. We show the importance of charge trapping in limiting not only the sensitivity but also the resolution of these detectors. Limitations on the maximum acceptable dark current and the corresponding charge collection efficiency jointly impose a practical constraint that many photoconductors fail to satisfy. We discuss the case of a-Se in which the dark current was brought down by three orders of magnitude by the use of special blocking layers to satisfy the dark current constraint. There are also a number of polycrystalline photoconductors, HgI2 and PbO being good examples, that show potential for commercialization in the same way that multilayer stabilized a-Se x-ray photoconductors were developed for commercial applications. We highlight the unique nature of avalanche multiplication in a-Se and how it has led to the development of the commercial HARP video-tube. An all solid state version of the HARP has been recently demonstrated with excellent avalanche gains; the latter is expected to lead to a number of novel imaging device applications that would be quantum noise limited. While passive pixel sensors use one TFT (thin film transistor) as a switch at the pixel, active pixel sensors (APSs) have two or more transistors and provide gain at the pixel level. The advantages of APS based x-ray imagers are also discussed with examples.
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Affiliation(s)
- Safa Kasap
- Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK, S7N 5A9, Canada; E-Mails: (J.B.F.); (G.B.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-306-966-5390; Fax: +1-306-966-5407
| | - Joel B. Frey
- Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK, S7N 5A9, Canada; E-Mails: (J.B.F.); (G.B.)
| | - George Belev
- Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK, S7N 5A9, Canada; E-Mails: (J.B.F.); (G.B.)
| | - Olivier Tousignant
- Anrad Corporation, 4950 rue Lévy, Saint-Laurent, QC, H4R 2P1, Canada; E-Mails: (O.T.); (H.M.); (J.G.); (L.L.)
| | - Habib Mani
- Anrad Corporation, 4950 rue Lévy, Saint-Laurent, QC, H4R 2P1, Canada; E-Mails: (O.T.); (H.M.); (J.G.); (L.L.)
| | - Jonathan Greenspan
- Anrad Corporation, 4950 rue Lévy, Saint-Laurent, QC, H4R 2P1, Canada; E-Mails: (O.T.); (H.M.); (J.G.); (L.L.)
| | - Luc Laperriere
- Anrad Corporation, 4950 rue Lévy, Saint-Laurent, QC, H4R 2P1, Canada; E-Mails: (O.T.); (H.M.); (J.G.); (L.L.)
| | - Oleksandr Bubon
- Department of Physics, Lakehead University, 955 Oliver Road, Thunder Bay, ON, P7B 5E1, Canada; E-Mails: (O.B.); (A.R.)
| | - Alla Reznik
- Department of Physics, Lakehead University, 955 Oliver Road, Thunder Bay, ON, P7B 5E1, Canada; E-Mails: (O.B.); (A.R.)
- Thunder Bay Regional Research Institute, 980 Oliver Road, Thunder Bay, ON, P7B 6V4, Canada; E-Mails: (G.D.); (J.A.R.)
| | - Giovanni DeCrescenzo
- Thunder Bay Regional Research Institute, 980 Oliver Road, Thunder Bay, ON, P7B 6V4, Canada; E-Mails: (G.D.); (J.A.R.)
| | - Karim S. Karim
- Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada; E-Mail:
| | - John A. Rowlands
- Thunder Bay Regional Research Institute, 980 Oliver Road, Thunder Bay, ON, P7B 6V4, Canada; E-Mails: (G.D.); (J.A.R.)
- Imaging Research, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
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Zhao Q, Antonuk LE, El-Mohri Y, Wang Y, Du H, Sawant A, Su Z, Yamamoto J. Performance evaluation of polycrystalline HgI2 photoconductors for radiation therapy imaging. Med Phys 2010; 37:2738-48. [PMID: 20632584 DOI: 10.1118/1.3416924] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Electronic portal imaging devices based on megavoltage (MV), active matrix, flat-panel imagers (AMFPIs) are presently regarded as the gold standard in portal imaging for external beam radiation therapy. These devices, employing indirect detection of incident radiation by means of a metal plate plus phosphor screen combination, offer a quantum efficiency of only approximately 2% at 6 MV, leading to a detective quantum efficiency (DQE) of only approximately 1%. In order to significantly improve the DQE performance of MV AMFPIs, a strategy based on the development of direct detection imagers incorporating thick films of polycrystalline mercuric iodide (HgI2) photoconductor was undertaken and is reported. METHODS Two MV AMFPI prototypes, one incorporating an approximately 300 microm thick HgI2 layer created through physical vapor deposition (PVD) and a second incorporating an approximately 460 microm thick HgI2 layer created through screen-printing of particle-in-binder (PIB) material, were quantitatively evaluated using a 6 MV photon beam. The reported measurements include empirical determination of x-ray sensitivity, lag, modulation transfer function (MTF), noise power spectrum, and DQE. RESULTS For both prototypes, MTF and DQE results were found to be consistent with theoretical expectations and the MTFs were also found to be higher than that measured from a conventional MV AMFPI. In addition, the DQE results exhibit input-quantum-limited behavior, even at extremely low doses. Compared to PVD, the PIB prototype exhibits much lower dark current, slightly higher lag, and similar DQE. Finally, the challenges associated with this approach, as well as strategies for achieving considerably higher DQE through thicker HgI2 layers, are discussed. CONCLUSIONS The DQE of each of the prototypes is found to be comparable to that of conventional MV AMFPIs, commensurate with the modest photoconductor thicknesses of these early samples. It is anticipated that thicker layers of HgI2 based on PIB deposition can provide higher DQE while maintaining good material properties.
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Affiliation(s)
- Qihua Zhao
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48019, USA.
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18
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Antonuk LE, Zhao Q, El-Mohri Y, Du H, Wang Y, Street RA, Ho J, Weisfield R, Yao W. An investigation of signal performance enhancements achieved through innovative pixel design across several generations of indirect detection, active matrix, flat-panel arrays. Med Phys 2009; 36:3322-39. [PMID: 19673228 DOI: 10.1118/1.3049602] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Active matrix flat-panel imager (AMFPI) technology is being employed for an increasing variety of imaging applications. An important element in the adoption of this technology has been significant ongoing improvements in optical signal collection achieved through innovations in indirect detection array pixel design. Such improvements have a particularly beneficial effect on performance in applications involving low exposures and/or high spatial frequencies, where detective quantum efficiency is strongly reduced due to the relatively high level of additive electronic noise compared to signal levels of AMFPI devices. In this article, an examination of various signal properties, as determined through measurements and calculations related to novel array designs, is reported in the context of the evolution of AMFPI pixel design. For these studies, dark, optical, and radiation signal measurements were performed on prototype imagers incorporating a variety of increasingly sophisticated array designs, with pixel pitches ranging from 75 to 127 microm. For each design, detailed measurements of fundamental pixel-level properties conducted under radiographic and fluoroscopic operating conditions are reported and the results are compared. A series of 127 microm pitch arrays employing discrete photodiodes culminated in a novel design providing an optical fill factor of approximately 80% (thereby assuring improved x-ray sensitivity), and demonstrating low dark current, very low charge trapping and charge release, and a large range of linear signal response. In two of the designs having 75 and 90 microm pitches, a novel continuous photodiode structure was found to provide fill factors that approach the theoretical maximum of 100%. Both sets of novel designs achieved large fill factors by employing architectures in which some, or all of the photodiode structure was elevated above the plane of the pixel addressing transistor. Generally, enhancement of the fill factor in either discrete or continuous photodiode arrays was observed to result in no degradation in MTF due to charge sharing between pixels. While the continuous designs exhibited relatively high levels of charge trapping and release, as well as shorter ranges of linearity, it is possible that these behaviors can be addressed through further refinements to pixel design. Both the continuous and the most recent discrete photodiode designs accommodate more sophisticated pixel circuitry than is present on conventional AMFPIs--such as a pixel clamp circuit, which is demonstrated to limit signal saturation under conditions corresponding to high exposures. It is anticipated that photodiode structures such as the ones reported in this study will enable the development of even more complex pixel circuitry, such as pixel-level amplifiers, that will lead to further significant improvements in imager performance.
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Affiliation(s)
- Larry E Antonuk
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109, USA.
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El-Mohri Y, Antonuk LE, Koniczek M, Zhao Q, Li Y, Street RA, Lu JP. Active pixel imagers incorporating pixel-level amplifiers based on polycrystalline-silicon thin-film transistors. Med Phys 2009; 36:3340-55. [PMID: 19673229 PMCID: PMC2805355 DOI: 10.1118/1.3116364] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 03/17/2009] [Accepted: 03/18/2009] [Indexed: 12/31/2022] Open
Abstract
Active matrix, flat-panel imagers (AMFPIs) employing a 2D matrix of a-Si addressing TFTs have become ubiquitous in many x-ray imaging applications due to their numerous advantages. However, under conditions of low exposures and/or high spatial resolution, their signal-to-noise performance is constrained by the modest system gain relative to the electronic additive noise. In this article, a strategy for overcoming this limitation through the incorporation of in-pixel amplification circuits, referred to as active pixel (AP) architectures, using polycrystalline-silicon (poly-Si) TFTs is reported. Compared to a-Si, poly-Si offers substantially higher mobilities, enabling higher TFT currents and the possibility of sophisticated AP designs based on both n- and p-channel TFTs. Three prototype indirect detection arrays employing poly-Si TFTs and a continuous a-Si photodiode structure were characterized. The prototypes consist of an array (PSI-1) that employs a pixel architecture with a single TFT, as well as two arrays (PSI-2 and PSI-3) that employ AP architectures based on three and five TFTs, respectively. While PSI-1 serves as a reference with a design similar to that of conventional AMFPI arrays, PSI-2 and PSI-3 incorporate additional in-pixel amplification circuitry. Compared to PSI-1, results of x-ray sensitivity demonstrate signal gains of approximately 10.7 and 20.9 for PSI-2 and PSI-3, respectively. These values are in reasonable agreement with design expectations, demonstrating that poly-Si AP circuits can be tailored to provide a desired level of signal gain. PSI-2 exhibits the same high levels of charge trapping as those observed for PSI-1 and other conventional arrays employing a continuous photodiode structure. For PSI-3, charge trapping was found to be significantly lower and largely independent of the bias voltage applied across the photodiode. MTF results indicate that the use of a continuous photodiode structure in PSI-1, PSI-2, and PSI-3 results in optical fill factors that are close to unity. In addition, the greater complexity of PSI-2 and PSI-3 pixel circuits, compared to that of PSI-1, has no observable effect on spatial resolution. Both PSI-2 and PSI-3 exhibit high levels of additive noise, resulting in no net improvement in the signal-to-noise performance of these early prototypes compared to conventional AMFPIs. However, faster readout rates, coupled with implementation of multiple sampling protocols allowed by the nondestructive nature of pixel readout, resulted in a significantly lower noise level of approximately 560 e (rms) for PSI-3.
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Affiliation(s)
- Youcef El-Mohri
- Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan 48109 USA.
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