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Scientist Award and Semiconductor Materials

Session chair: Sellin , Paul (University of Surrey, Department of Physics, Guildford, UK); Takahashi , Tadayuki (The University of Tokyo, Kavli IPMU, Kashiwa, Japan)
Shortcut: R-09
Date: Thursday, 21 October, 2021, 11:45 AM - 1:45 PM
Room: RTSD
Session type: RTSD Session


Click on an contribution to preview the abstract content.

11:45 AM R-09-01

RTSD Scientist Award (#313)

R. B. James1, T. Takahashi2

1 Savannah River National Laboratory, Science & Technology Directorate, Aiken, South Carolina, United States of America
2 The University of Tokyo, Kavli IPMU, Chiba, Japan


RTSD Scientist Award:

This is not a technical presentation; it is an introduction of the 2021 RTSD Scientist Award recipient.

This presentation recognizes an individual who has made high-impact contributions to the development of room-temperature semiconductor detector technology. The RTSD Steering Committee begins the selection process by nominating worthy individuals, followed by identifying the finalists and casting votes for them.

The first RTSD Scientist Award recipient was in 2001, and the award has been given at each RTSD Symposium since then. Past awardees included, in order of receipt: Paul Siffert, Ralph James, Michael Schieber, Arnold Burger, Michael Fiederle, Csaba Szeles, Zhong He, Henry Chen, Aleksey Bolotnikov, Larry Franks, Jan Iwanczyk, Andrea Zappettini, Krishna Mandal, Giuseppe Bertuccio, and Kanai Shah.

Please join us to recognize the 2021 RTSD Scientist Award recipient.

Keywords: RTSD, Award
11:55 AM R-09-02

Organic semiconductors and perovskites as room temperature solid state radiation detectors (#1460)

B. Fraboni1

1 University of Bologna, Department of Physics and Astronomy, Bologna, Italy


The recent impressive progress in the field of organic semiconductors and perovskites (both in terms of material technologies and device development) assessed their large potential for the implementation of innovative and unprecedented applications. Their use in the direct detection of ionizing radiation is compelling, as they can satisfy most of the major X-ray detector requirements, coupled to unique properties such as solution-processability, cost-effective fabrication, scalability to large area systems and the use of limited amounts of earth-abundant precursors. In particular, the human-tissue equivalence of organic material is a peculiar feature extremely relevant for their application in medical dosimetry, while perovskites are characterized by a strong absorption of ionizing radiation, due to the presence of heavy atoms as Pb, I, Br, together with high charge carrier mobilities, long exciton diffusion and long charge carrier lifetime.

Recent results on X-ray direct detectors fabricated from solution-grown organic semiconductors and perovskites (in single crystal or thin film form) will be critically discussed together with the fundamental principles and models underlying the observed X-ray detection processes.

Keywords: organic semiconductors, perovskites, room temperature radiation detectors
12:25 PM R-09-03

Designing curved organic-inorganic hybrid X-ray detectors: Effect of organic semiconductor molecular weight (#1034)

M. P. A. Nanayakkara1, M. G. Masteghin1, L. Basiricò2, 3, I. Fratelli2, 3, A. Ciavatti2, 3, B. Fraboni2, 3, I. Jayawardena1, S. R. P. Silva1

1 University of Surrey, Advanced Technology Institute, Guildford, United Kingdom
2 University of Bologna, Department of Physics and Astronomy, Bologna, Italy
3 National Institute for Nuclear Physics, INFN section of Bologna, Bologna, Italy


Curved X-ray detectors are appealing for a wide range of applications such as medical imaging and security screening. This is due to several benefits including reduced image distortion and vignetting compared to their planar counterparts. Fabrication of curved detectors based on inorganic semiconductors is restricted by their brittle nature. In comparison, organic-inorganic hybrid semiconductor based on high attenuating bismuth oxide nanoparticles in an organic bulk heterojunction consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) is promising in this regard. However, the influence of organic semiconductor (P3HT) molecular weight on achieving an optimum balance between detector performance and bendability characteristics of curved detectors still remains less well understood. In this study, higher P3HT molecular weights are identified to be suitable for the fabrication of curved detectors. Such curved detectors can be bent to a radius as low as 1.3 mm with low deviation in detector performance even after 100 repeated bending cycles while maintaining an industry-standard dark current of <1 pA mm-2 and sensitivity of ~0.17 μC Gy-1 cm-2. This work highlights the importance of understanding fundamental design parameters such as semiconducting molecular weight, a factor that has not been explored by the radiation detector community yet.

Keywords: flexible, molecular weight, radiation detectors
12:40 PM R-09-04

An Organic Perovskite-Graphene Device for Radiation Detection (#1176)

J. Snow1, W. Nie2, E. Torres4, K. Shirley3, E. Cazalas1

1 University of Utah, Civil Engineering, Salt Lake City, Utah, United States of America
2 Los Alamos National Labs, Sante Fe, New Mexico, United States of America
3 Kairos, LLC, Clayton, United States of America
4 Graphenea, Donostia-San Sebastian Guipúzcoa, Spain

On behalf of Kairos, LLC-Collaboration


Perovskite materials are proven to be highly sensitive to electromagnetic radiation. However, retrieving individual pulse data with specifically organic perovskite materials is difficult. This study examines a novel organic perovskite-graphene device for radiation detection. With this device architecture, a layer of graphene responds to the internal field created inside of the organic perovskite material via field effect. We have seen consistent current response levels with this design when irradiated with X-rays at varying voltage and current. When compared to previous studies performed with inorganic perovskite material, this novel design provides an easier and more cost-effective route to production of perovskite radiation detectors. Future work with this device will attempt to achieve single pulses from charged particles.


We thank Elias Torres at Graphenea for providing for the graphene transistors utilized in the fabrication of the full device structures.

Keywords: X-ray, radiation, detection, perovskite, semiconductor
12:55 PM R-09-05

Direct Detection of 5 MeV Protons by Flexible Organic Thin Film DevicesDirect Detection of 5 MeV Protons by Flexible Organic Thin Film Devices (#960)

I. Fratelli1, E. Zanazzi2, L. Basiricò1, A. Ciavatti1, M. Chiari3, J. Anthony4, A. Quaranta2, B. Fraboni5

1 University of Bologna, Physics and Astronomy, Bologna, Italy
2 University of Trento, Industrial Engineering, Trento, Italy
3 INFN, LABEC, Firenze, Italy
4 University of Kentucky, Chemistry, Lexington, Kentucky, United States of America
5 University of Bologna, Department of Physics and Astronomy, Bologna, Italy


The direct detection of 5 MeV protons by flexible organic detectors based on thin films is here demonstrated. The organic devices act as a solid-state detector in which the energy released by the protons within the active layer of the sensor is converted into an electrical current. The sensors demonstrate a stable and reproducible response to proton beams in a range of fluences between 3.5 · 109 H+cm-2 and 8.7 · 1011 H+cm-2 and maintain a linear response up to a total dose of 28.5 kGy. By exploiting the structure of this sensor, two different operation modes can be effectively used: i) real-time mode sensing, where the amount of charges generated and collected at the electrodes is proportional to the released dose; ii) integration-mode sensing, where the energy released in the plastic substrate by the impinging protons generates static long lifetime charges that accumulate in the polymeric substrate and induce an increase of conductivity in the semiconducting layer. This study shows how to detect and exploit the energy absorbed both by the organic semiconducting layer and by the plastic substrate, allowing to extrapolate information on the present and the past irradiation of the detector. The measured sensitivity S = (5.15 ± 0.13) pC Gy-1 and limit of detection LOD = (30 ± 6) cGy s-1, of the here proposed detectors assess their efficacy and their potential as proton dosimeters in several fields of application, such as in medical proton-therapy

Keywords: organic semiconductors, real time dosimeter, direct proton detection
1:10 PM R-09-06

Ga2O3: A new class of radiation detector material (#1121)

G. Yang1, J. Blevins1, R. B. James2

1 North Carolina State University, Department of Nuclear Engineering, Raleigh, North Carolina, United States of America
2 Savannah River National Laboratory, Aiken, South Carolina, United States of America


Ga2O3 is an ultra-wide bandgap semiconductor with growing interest in exploring its radiation detection capabilities. The unique physical properties of this emerging material enable its great potential to work in extreme conditions. Ga2O3 materials can be used as both semiconductor detectors and scintillator detectors. In this presentation, we report our progress in developing Ga2O3 materials for radiation detection at different temperatures. Fe-doped Ga2O3 is characterized in terms of its potential spectroscopic abilities for both scintillation and semiconductor analysis. It was found that the scintillation light yield of Ga2O3 is comparable to the reference BGO crystal, making it a viable candidate for scintillation-based spectroscopic work. Meanwhile, we observed that Ga2O3:Fe has an ultra-high resistivity of nearly 1014 cm at room temperature. High temperature experiments up to 370 K showed this resistivity can still be maintained at 1012 cm, which provides the benefit to enable high signal-to-noise ratio for high-temperature radiation detection. Detailed material characterization and detection analysis will be offered in this presentation.

AcknowledgmentThis work was partially supported by the US Department of Energy (DOE) under Award Number DE-SC0021028.
Keywords: Ga2O3, Radiation Detectors, Temperature, Semiconductor, Scintillator
1:25 PM R-09-07

Results of alpha irradiation of diamond sensors (#1048)

G. Giacomini1, G. Carini1, C. R. Deane1, A. Dellapenna1, G. Deptuch1, L. Fabris2, S. Herrmann1, J. Kierstead1, I. Kotov1, S. Mcconchie2, E. Muller1, G. Pinaroli1, D. Pinelli1, S. Rescia1, E. Rossi1

1 Brookhaven National Laboratory, Upton, New York, United States of America
2 Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America


In a neutron generator, deuterium ions are accelerated towards a tritium-loaded target. From the nuclear reaction that may result from their interaction, an alpha particle and a neutron are emitted back-to-back. The neutron escaping the chamber can be used for tomography of a high-Z, its trajectory calculated also from the hit position of the alpha, much easier to detect. This technique is called Associated Particle Imaging (API).  Existing API systems, available commercially, have several limitations: a semiconductor-based API detector placed inside the vacuum chamber is believed to surpass all previous families of API detectors. In the past years, we have shown how silicon can withstand the alpha fluence expected during the neutron generator lifetime. As such, it will be the semiconductor material of choice for our API detector. However, looking forward to an upgrade, we wanted to evaluate the radiation hardness against alphas of diamond sensors, which is another kind of detector that is routinely fabricated at BNL. We exposed a single channel diamond sensor, mounted on the same set-up used for the irradiation tests on silicon diodes, to the same radioactive source used during the silicon irradiation: a 5 MeV alpha flux generated by an 241Am radioactive source. During irradiation, the diode was biased at a positive voltage and waveforms were acquired from time to time at positive and negative voltages, while data analysis was performed off-line.  By the time of the conference, we will have accumulated data describing the evolution of the diamond behavior after over 5000 hours of continuous alpha irradiation.

Keywords: diamond detectors, alpha particles, radiation hardness

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