Evidence for Defect-Mediated Tunneling in Hexagonal Boron Nitride-Based Junctions
Evidence for Defect-Mediated Tunneling in Hexagonal Boron Nitride-Based Junctions
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DOI：
10.1021/acs.nanolett.5b02625
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发表时间：
2015-11-01
期刊：
影响因子：
10.8
通讯作者：
Eisenstein, J. P.
中科院分区：
文献类型：
--
作者：
Chandni, U.;Watanabe, K.;Eisenstein, J. P.
我们研究了六方氮化硼（hBN）原子级薄层的电子隧穿。采用金属（Cr/Au）和半金属（石墨）对电极。虽然直接隧穿电阻如预期的那样随着势垒厚度几乎呈指数增加，但较厚的结也表现出明显的库仑阻塞特征，包括零偏压附近的隧道电流的强烈抑制和较大偏压下电流中的阶梯状特征。这些步骤的电压分离表明，hBN阻挡层中纳米级缺陷的单电子充电是这些签名的原因。我们发现，退火的金属-hBN-金属结去除这些缺陷和库仑阻塞签名的隧道电流。
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.