Ortuño M, Somoza A M, Vinokur V M, Baturina T I
Departamento de Física - CIOyN, Universidad de Murcia, Murcia 30071, Spain.
Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
Sci Rep. 2015 Apr 10;5:9667. doi: 10.1038/srep09667.
There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screening length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.
近年来，在工程高介电常数二维（2D）材料方面取得了显著进展，这些材料正被积极用于纳米电子学中的电容器和存储器件、能量存储以及通信器件中的高频调制。然而，这些系统的许多独特性质仍未得到充分理解，有待进一步探索。在此，我们报告了对模拟二维绝缘体的电容器横向网络的跳跃电导率的数值研究，并证明二维长程库仑相互作用会导致特殊的尺寸效应。我们发现，决定电子输运的特征能量与系统尺寸或静电屏蔽长度呈对数关系，具体取决于哪一个更短。我们的结果不仅适用于当前的研究背景，例如，还解释了在超导体 - 绝缘体转变临界附近薄超导膜电导率对数尺寸依赖性的近期实验观察结果，此时会出现巨大的介电常数。我们的发现与二维系统中电导率是材料局部特性的传统观点截然不同，并确立了其宏观全局特性作为高介电常数二维纳米材料的一般属性。
