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Layered BiOI single crystals capable of detecting low dose rates of X-rays

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Jagt, Robert A 
Bravić, Ivona 
Gałkowski, Krzysztof 
Borowiec, Joanna 


jats:titleAbstract</jats:title>jats:pDetecting low dose rates of X-rays is critical for making safer radiology instruments, but is limited by the absorber materials available. Here, we develop bismuth oxyiodide (BiOI) single crystals into effective X-ray detectors. BiOI features complex lattice dynamics, owing to the ionic character of the lattice and weak van der Waals interactions between layers. Through use of ultrafast spectroscopy, first-principles computations and detailed optical and structural characterisation, we show that photoexcited charge-carriers in BiOI couple to intralayer breathing phonon modes, forming large polarons, thus enabling longer drift lengths for the photoexcited carriers than would be expected if self-trapping occurred. This, combined with the low and stable dark currents and high linear X-ray attenuation coefficients, leads to strong detector performance. High sensitivities reaching 1.1  × 10jats:sup3</jats:sup> μC Gyjats:subair</jats:sub>jats:sup−1</jats:sup> cmjats:sup−2</jats:sup> are achieved, and the lowest dose rate directly measured by the detectors was 22 nGyjats:subair</jats:sub> sjats:sup−1</jats:sup>. The photophysical principles discussed herein offer new design avenues for novel materials with heavy elements and low-dimensional electronic structures for (opto)electronic applications.</jats:p>


Acknowledgements: We would like to thank Prof. Richard Phillips (University of Cambridge) for useful feedback on the manuscript and help with optical measurements. The authors also thank Zhuotong (Thomas) Sun (University of Cambridge) for assistance on the powder X-ray diffraction measurements, and Prof. James Marrow and Marcus Williamson (University of Oxford) for assistance in taking radiographs. R.A.J. acknowledges funding from an EPSRC Department Training Partnership studentship (no. EP/N509620/1), as well as Bill Welland and the Winton Programme for the Physics of Sustainability. L.E. and T.V.D.G. acknowledge support from the EPSRC Cambridge NanoDTC (no. EP/L015978/1). L.E. acknowledges funding by the DFG (project no. 387651688). T.V.D.G. also acknowledges financial support from the Schiff Foundation. K.G. and S.D.S. acknowledge the EPSRC (no. EP/R023980/1) for funding. S.D.S. acknowledges the Royal Society and Tata Group (no. UF150033) and EPSRC (no. EP/W004445/1) for funding. The work has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (HYPERION - grant agreement no. 756962; PEROVSCI - 957513). The work was supported by a Royal Society International Exchanges Cost Share award (no. IEC\R2\170108) and the Alliance Hubert Curien Programme of the British Council (no. 608412749). K.R.D. thanks the Department of Chemistry at the University of Oxford for a studentship. P.P. appreciates support from National Science Centre Poland within the OPUS program (no. 2019/33/B/ST3/01915). This work was partially supported by OPEP project, which received funding from the ANR-10-LABX-0037-NEXT. The Polish participation in European Magnetic Field Laboratory is supported by the DIR/WK/2018/07 grant from Ministry of Science and Higher Education, Poland. F.D. acknowledges support from the DFG Emmy Noether Programme (project no. 387651688) and the Winton Programme for the Physics of Sustainability. J.L.M.-D. acknowledges funding from the Royal Academy of Engineering under the Chair in Emerging Technologies Scheme (no. CIET1819_24). R.L.Z.H. acknowledges support from the Royal Academy of Engineering under the Research Fellowship scheme (no. RF\201718\1701), the Isaac Newton Trust (Minute 19.07(d)), Downing College Cambridge through the Kim and Juliana Silverman Research Fellowship, and an EPSRC grant (no. EP/V014498/2). I.B. and B.M. acknowledge support from the Winton Programme for the Physics of Sustainability. B.M. also acknowledges support from a UKRI Future Leaders Fellowship (no. MR/V023926/1) and from the Gianna Angelopoulos Programme for Science, Innovation and Technology. The calculations are conducted using resources provided by the Cambridge Tier-2 system, operated by the University of Cambridge Research Computing Service ( and funded by EPSRC Tier-2 capital grant (no. EP/P020259/1).


Article, /639/301/119/995, /639/301/1005/1007, /119/118, /120, /128, /140/125, /140/133, /145, article

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Nature Communications

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Springer Science and Business Media LLC
Royal Academy of Engineering (RF\201718\1701, CIET1819_24)
Isaac Newton Trust (Minute 19.07(d))
RCUK | Engineering and Physical Sciences Research Council (EPSRC) (EP/V014498/1, EP/N509620/1, EP/L015978/1, EP/R023980/1, EP/L015978/1)., EP/R023980/1, EP/P020259/1)
Royal Society (UF150033)
EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 European Research Council (H2020 Excellent Science - European Research Council) (756962)