Zhang Peng
Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104, USA.
Sci Rep. 2015 May 19;5:9826. doi: 10.1038/srep09826.
When two conductors are separated by a sufficiently thin insulator, electrical current can flow between them by quantum tunneling. This paper presents a self-consistent model of tunneling current in a nano- and subnano-meter metal-insulator-metal plasmonic junction, by including the effects of space charge and exchange correlation potential. It is found that the J-V curve of the junction may be divided into three regimes: direct tunneling, field emission, and space-charge-limited regime. In general, the space charge inside the insulator reduces current transfer across the junction, whereas the exchange-correlation potential promotes current transfer. It is shown that these effects may modify the current density by orders of magnitude from the widely used Simmons' formula, which is only accurate for a limited parameter space (insulator thickness > 1 nm and barrier height > 3 eV) in the direct tunneling regime. The proposed self-consistent model may provide a more accurate evaluation of the tunneling current in the other regimes. The effects of anode emission and material properties (i.e. work function of the electrodes, electron affinity and permittivity of the insulator) are examined in detail in various regimes. Our simple model and the general scaling for tunneling current may provide insights to new regimes of quantum plasmonics.
当两个导体被足够薄的绝缘体隔开时，电流可以通过量子隧穿在它们之间流动。本文通过考虑空间电荷和交换关联势的影响，提出了一种纳米和亚纳米级金属-绝缘体-金属等离子体结中隧穿电流的自洽模型。研究发现，该结的J-V曲线可分为三个区域：直接隧穿、场发射和空间电荷限制区。一般来说，绝缘体内的空间电荷会降低结间的电流传输，而交换关联势则会促进电流传输。结果表明，这些效应可能会使电流密度与广泛使用的西蒙斯公式相比有几个数量级的变化，西蒙斯公式仅在直接隧穿区域的有限参数空间（绝缘体厚度>1nm且势垒高度>3eV）内准确。所提出的自洽模型可以在其他区域对隧穿电流进行更准确的评估。在不同区域详细研究了阳极发射和材料特性（即电极的功函数、绝缘体的电子亲和能和介电常数）的影响。我们的简单模型和隧穿电流的一般标度关系可能为量子等离子体学的新领域提供见解。
