Evidence for Defect-Mediated Tunneling in Hexagonal Boron Nitride-Based Junctions.
We investigate electron tunneling through atomically thin layers of hexagonal boron nitride (hBN). Metal (Cr/Au) and semimetal (graphite) counter-electrodes are employed. While the direct tunneling resistance increases nearly exponentially with barrier thickness as expected, the thicker junctions also exhibit clear signatures of Coulomb blockade, including strong suppression of the tunnel current around zero bias and step-like features in the current at larger biases. The voltage separation of these steps suggests that single-electron charging of nanometer-scale defects in the hBN barrier layer are responsible for these signatures. We find that annealing the metal-hBN-metal junctions removes these defects and the Coulomb blockade signatures in the tunneling current.
Institute for Quantum Information and Matter, Department of Physics, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States.
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U
Chandni
National Institute for Materials Science , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
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K
Watanabe
National Institute for Materials Science , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
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Taniguchi
Institute for Quantum Information and Matter, Department of Physics, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States.
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JP
Eisenstein
Tunneling; annealing; coulomb blockade; graphite; hBN defects; hexagonal boron nitride (hBN)