Positron Charge Sensing Using Two-Dimensional Materials

ORAL

Abstract

Traditionally, Positron Annihilation Spectroscopy (PAS) uses the detection of 511 keV photons that are emitted following a positron and an electron collision and annihilation. We aim to extend the utility of PAS by using charge-sensing devices. We fabricate sensitive field-effect transistors based on two-dimensional materials such as graphene, which are used as sensitive charge probes. Our devices measure the accumulated positive charge caused by the annihilation events in the solid and can be used in the future as tools for the study of positrons in solids [1,2].

We utilized a high-mobility double-gated graphene field-effect transistor to measure the accumulated charge created by positron annihilation in its back-gate. I will describe the use of graphene devices under DC, reaching a positron current sensitivity of 1.2 fA/√Hz, <!--[if gte msEquation 12]> lang=EN-US style='font-size:12.0pt;font-family:"Cambria Math",serif;
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mso-bidi-theme-font:major-bidi;mso-ansi-language:EN-US'> style='mso-bidi-font-style:normal'>Hz detected over 20 min [1]. I will also describe our RF devices, reaching a sensitivity of 0.01 fA/√Hz, corresponding to ~100 positrons/sec. In these RF graphene-based devices, the graphene is coupled to a waveguide and is integrated as an RF resonator, where annihilation events are detected through changes in the graphene RF reflection coefficient S11. It is designed for charge-detection of positrons in micro-second time-resolution, aiming to detect single positron annihilation events. Using a table-top 22Na positron source, we demonstrate the utility of two-dimensional layered materials as probes for the charging dynamics of positrons in solids. In the future, we intend to integrate these devices inside the SPOT-IL slow positron beam [3, 4], built at the Hebrew University of Jerusalem.

*Devices for this study were fabricated at the Center for Nanoscience and Nanotechnology, the Hebrew University. Funding for this work was provided by the IAEC through Pazy grant 328/20, and by the Israel Science Foundation grant 861/19. P.O is supported by a fellowship by the ministry of science and technology, Israel. T.R.D. acknowledges support from the Lady Davis Postdoctoral Fellowship program. K.W. and T.T. acknowledge sup-port from the Elemental Strategy Initiative conducted by the MEXT, Japan (Grant Number JPMXP0112101001) and JSPS KAKENHI (Grant Numbers JP19H05790 and JP20H00354).

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Publication: [1] Or, Paz et al. "Positron charge sensing using a double-gated graphene field effect transistor." Review of Scientific Instruments 93.1 (2022): 015002.
[2] Or, Paz et al. "Graphene-based positron charge sensor". Applied Physics Letters 113, no. 15: 154101. (2018)
[3] Or, Paz et al. "SPOT IL-Slow positron facility in Israel." AIP Conference Proceedings. Vol. 2182. No. 1. AIP Publishing LLC (2019).
[4] Or, Paz et al. "The SPOT-IL Positron Beam Construction and Its Use for Doppler Broadening Measurement of Titanium Thin Films". arXiv preprint arXiv:2007.05921 (2020).

Presenters

  • Paz Or

    • The Hebrew University of Jerusalem

Authors

  • Paz Or

    • The Hebrew University of Jerusalem

  • Omer Kotlovsky

    • The Hebrew University of Jerusalem

  • Devidas T R

    • Hebrew University of Jerusalem

  • Matan Hadad

    • The Hebrew University of Jerusalem

  • Roi Abir

    • The Hebrew University of Jerusalem

  • Takashi Taniguchi

    • National Institute for Materials Science
    • Kyoto Univ
    • International Center for Materials Nanoarchitectonics, National Institute of Materials Science
    • Kyoto University
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-044, Japan
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science
    • National Institute for Materials Science, Japan
    • National Institute For Materials Science
    • NIMS
    • National Institute for Material Science
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
    • NIMS Japan

  • Kenji Watanabe

    • National Institute for Materials Science
    • Research Center for Functional Materials, National Institute of Materials Science
    • Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-044, Japan
    • NIMS
    • Research Center for Functional Materials, National Institute for Materials Science
    • National Institute for Materials Science, Japan
    • Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
    • NIMS Japan

  • Iris Sabo-Napadensky

    • Soreq NRC

  • Sharon May-Tal Beck

    • Physics department, NRCN

  • Guy Ron

    • Hebrew University of Jerusalem

  • Hadar Steinberg

    • Hebrew University of Jerusalem