Positron charge sensing using a double-gated graphene field effect transistor

We utilize a high-mobility double-gated graphene field-effect transistor to measure the accumulated charge created by positron annihilation in its back-gate. The device consists of an exfoliated graphene flake stacked between two hexagonal boron nitride flakes placed on a 1 cm2 substrate of 500 μm t...

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Veröffentlicht in:Review of scientific instruments 2022-01, Vol.93 (1), p.015002-015002
Hauptverfasser: Or, Paz, Devidas, T. R., Taniguchi, Takashi, Watanabe, Kenji, Sabo-Napadesky, Iris, May-Tal Beck, Sharon, Ron, Guy, Steinberg, Hadar
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Sprache:eng
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Zusammenfassung:We utilize a high-mobility double-gated graphene field-effect transistor to measure the accumulated charge created by positron annihilation in its back-gate. The device consists of an exfoliated graphene flake stacked between two hexagonal boron nitride flakes placed on a 1 cm2 substrate of 500 μm thick conducting p-doped Si capped by 285 nm-thick SiO2. The device is placed in close proximity to a 780 kBq 22Na positron source emitting a constant flux of positrons. During the measurement, positrons annihilate within the back-gate, kept floating using a low-capacitance relay. The accumulated positive charge capacitively couples to the graphene device and builds a positive voltage, detectable through a shift in the top-gate dependent graphene resistance characteristic. The shift in the position of the top-gate Dirac peak is then used for extracting the exact voltage buildup and quantitative evaluation of the accumulated charge. Reaching a positron current sensitivity of ∼1.2 fA/Hz, detected over 20 min, our results demonstrate the utility of two-dimensional layered materials as probes for charging dynamics of positrons in solids.
ISSN:0034-6748
1089-7623
DOI:10.1063/5.0069481