241Am alpha particle response in the defect perovskite Cs3Sb2I9: a candidate for room-temperature radiation detection (#2144)
K. M. McCall1, 2, Z. Liu2, C. C. Stoumpos1, W. Lin1, Y. He1, M. G. Kanatzidis1, B. W. Wessels2
1 Northwestern University, Department of Chemistry, Evanston, Illinois, United States of America
The wide bandgap semiconductors A3M2I9 (A = Cs+, Rb+ is an alkali metal; M = Sb3+, Bi3+ is a metal ion) are promising candidates for room-temperature gamma radiation detection. Hybrid halide perovskites have had tremendous success as highly efficient solar cell absorbers due to their long diffusion lengths and high absorption. The defect perovskites are inorganic halide perovskite derivatives similarly based on MI6 octahedra, and have received recent attention as stable alternatives to the hybrid halide perovskites. They have suitably wide bandgaps for detection (1.9-2.2 eV), and are absent of the toxic metals Cd, Hg, Tl, and Pb present in the leading semiconductor detector materials. These materials possess high densities and atomic numbers Z, and exhibit high resistivities of 1010-1012 Ω•cm. Furthermore, the layered crystal structures lead to facile growth of large single crystals and simplified device fabrication, as contact-ready surfaces can be readily cleaved from the pristine ingot. Initial results on Bridgman-grown single crystals found laser response in each compound besides Cs3Sb2I9, which showed no photoresponse. In this work, we report on an improved synthesis method for Cs3Sb2I9, which results in photoresponse to laser and response to Am241 alpha particle radiation. The alpha particle measurements are used to probe the charge transport characteristics, revealing an estimated mobility-lifetime product of 4.1 x 10-6 cm2/V for Cs3Sb2I9. Using the rise time of the alpha particle response pulse, the mobility is estimated to be 5.6 cm2/V•s. Defect studies including photoluminescence measurements and thermally-stimulated current spectroscopy are underway to push these values to their highest potential. These results and the continuing improvement in response demonstrate that Cs3Sb2I9 is a promising candidate for room-temperature radiation detection.
Keywords: defect perovskite, halide perovskite, semiconductor detector material
Charged defects in organometallic halide perovskite single crystals (#3966)
M. Ahmadi1, D. Hamm2, C. Seal2, J. Tisdale1, B. Hu1, E. D. Lukosi2
1 University of Tennessee, Knoxville, Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee, United States of America
In this paper, we investigate the charged defects in methylammonium lead iodide (MAPI) and methyl ammonium lead bromide (MAPB) single crystals for high energy radiation detectors. In this measurement, the capture cross section and energy level of electron or hole defects are measured as a function of temperature. We expect that identification of charged defects in perovskite semiconductors can help us mitigate their inclusion via growth and post-growth treatments and enhance their bulk charge collection efficiency properties for effective ionizing radiation detection.
Keywords: organometallic halide perovskite, radiation detector, defect, photo-induced current transient spectroscopy
Development of a SiC Schottky Diode for High Temperature Alpha Spectroscopy (#2251)
J. Jarrell1, T. Blue1, L. R. Cao1
1 The Ohio State University, Nuclear Engineering, Columbus, Ohio, United States of America
The vulnerability of a closed fuel cycle stems from the risk of diverting special nuclear materials (SNM) for ill-purposed use. There is a critical need to monitor the concentration of actinides in the molten salt at real-time during pyro-processing. We are developing a sensor prototype based on wide band-gap semiconductor materials for measurement of actinide concentrations in molten salt at a high temperature. The approach uses in-salt electro-deposition to pre-concentrate actinides onto a sensor before measurement, which will greatly increase the accuracy in actinides quantification for use in SNM accounting. A 320-micron thick 4H-SiC Schottky diode utilizing a 100-nm nickel contact and 10-nm platinum corrosion barrier layer was fabricated. This diode was fabricated as an alpha radiation sensor for a high temperature and corrosive environment. An Am-241 alpha spectrum was measured with the detector operating temperature ranging from room temperature to 500 °C. The resulting alpha spectra were characterized by centroid position and detector energy resolution. The energy resolution was found to be 0.94% at room temperature and increased to 2.2% at 500 °C. Improving detector resolution with increasing time under temperature suggests an annealing effect on the Schottky contact interface.
Keywords: 4H-SiC, Alpha Spectroscopy, Electrorefining, Schottky Diode, Pyroprocessing, Spent Nuclear Fuel
Growth and characterization of compound semiconductor TlPbI3 crystal for radiation detection (#2729)
V. Q. Phan1, H. Kim1
1 Kyungpook National University, Department of Physics, Daegu, Republic of Korea
We report our study on crystal growth and electrical properties of TlPbI3 perovskite crystal. TlPbI3 is a promising compound semiconductor candidate for room temperature radiation detection due to its wide energy band gap, high effective atomic number and high density. The low melting point and vapor pressure of this material resulted in not only simple growth technique but also the potential for reduction of impurity. In this study, the starting material is synthesized and purified by zone refining technique and the single crystal is grown by modified Bridgman furnace. Sample with the thickness of 1mm is cut using diamond-wise saw and polished to remove surface damages using nano-silica slurry. Electrodes of the initial device are made by sputtering gold and silver paste. In order to characterize properties of this material, the resistivity, I-V characteristic, and carrier mobility-lifetime products are measured. The fabricated device from this crystal shows linear respond with respect to the X-ray intensity.
Keywords: compound semiconductor, radiation detection, charge carrier mobility
Lessons from a Decade of BiI3 Gamma-Ray Sensor Development (#1157)
P. M. Johns1, 2, M. Bliss1, 2, J. E. Baciak1, J. C. Nino3
1 University of Florida, Materials Science and Engineering Department, Nuclear Engineering Program, Gainesville, Florida, United States of America
BiI3 has been investigated for its unique properties as a layered compound semiconductor for many decades. Among these are several qualities that make it an attractive candidate for a room temperature gamma ray detector (RTSD). However, despite the exceptional atomic, physical, and electronic properties of this material, good resolution gamma ray spectra had never been reported for BiI3. Over the past decade, development of this promising RTSD compound at the University of Florida has led to four Ph.D. theses focused around crystal growth, defect engineering, detector fabrication and processing optimization, and finally, the demonstration of good resolution spectral measurements at room temperature. The shortcomings that previously prevented BiI3 from reaching success as a gamma ray sensor have been identified and suppressed to unlock the performance of this promising compound. Included in this work are the results from studies on a number of methods which have, for the first time, enabled BiI3 to exhibit spectral performance rivaling many other candidate semiconductors for room temperature gamma ray sensors. New approaches to crystal growth have been explored that allow BiI3 spectrometers to be fabricated with up to 2.2% spectral resolution at 662 keV. Fundamental studies on trap states, dopant incorporation, and polarization were performed to enhance performance of this compound. Additionally, advanced detection techniques were applied to highlight the capability of high quality BiI3 spectrometers. Overall, through this work, BiI3 is now a strong candidate RTSD material with the potential to serve as a new state-of-the-art compound for applications in nuclear security and radiation detection sciences.
Keywords: Bismuth triiodide, defects, semiconductor, dopants, gamma-ray sensor
Thallium Bromide Devices with Thallium Contacts (#3409)
A. Datta1, J. Fiala1, P. Becla1, S. Motakef1
1 CapeSym, Inc., Natick, Massachusetts, United States of America
Thallium bromide (TlBr) is a wide bandgap, compound semiconductor with high gamma-ray stopping power and promising physical properties. The electro-migration of Br- ions towards anode and their reaction with the contact have been long known to adversely influence the lifetime of TlBr devices. The use of Tl contacts in lieu of Au or Pt was first pioneered by Hitomi and colleagues, and has the potential to reduce the effect of Br- ions on contact degradation and detector electronic noise. We report on the performance of TlBr devices with Tl contacts. Results indicate that vapor-deposited Tl-contacts are highly ohmic, and adhere strongly to TlBr. Long term lifetime tests were performed under alternating bias with an 8-hour duty cycle. Unlike devices with Pt and Au contacts, devices with Tl do not exhibit the short term (of the order of 100s of hours) fluctuations that are generally observed with other contact metals. Furthermore, these devices show a much more stable behavior. We will also report on the spectroscopic response of TlBr-devices with Tl-contacts. The safety considerations of TlBr devices with Tl-contacts were extensively explored and will be discussed.
This work was supported in part by the U.S. Department of Homeland Security, Domestic Nuclear Detection office contract HSHQDN-16-C-00022. This support does not constitute an express or implied endorsement on the part of the Government.
Keywords: Thallium electrodes, Semiconductor Fabrication