College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, China.
Physical Sciences and Engineering Division, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia.
Nano Lett. 2015 Dec 9;15(12):8136-40. doi: 10.1021/acs.nanolett.5b03575. Epub 2015 Nov 19.
The dielectric constant or relative permittivity (ε(r)) of a dielectric material, which describes how the net electric field in the medium is reduced with respect to the external field, is a parameter of critical importance for charging and screening in electronic devices. Such a fundamental material property is intimately related to not only the polarizability of individual atoms but also the specific atomic arrangement in the crystal lattice. In this Letter, we present both experimental and theoretical investigations on the dielectric constant of few-layer In2Se3 nanoflakes grown on mica substrates by van der Waals epitaxy. A nondestructive microwave impedance microscope is employed to simultaneously quantify the number of layers and local electrical properties. The measured ε(r) increases monotonically as a function of the thickness and saturates to the bulk value at around 6-8 quintuple layers. The same trend of layer-dependent dielectric constant is also revealed by first-principles calculations. Our results of the dielectric response, being ubiquitously applicable to layered 2D semiconductors, are expected to be significant for this vibrant research field.
介电常数或相对介电常数（ε(r)）是描述介质中净电场相对于外场减小程度的介电材料的一个重要参数，它对于电子设备中的充电和屏蔽至关重要。这种基本材料特性不仅与单个原子的极化率有关，而且与晶体点阵中的特定原子排列有关。在这封信中，我们通过范德华外延法在云母衬底上生长的少层 In2Se3 纳米片中进行了实验和理论研究。我们采用非破坏性微波阻抗显微镜来同时量化层数和局部电性能。测量得到的 ε(r)随厚度单调增加，并在约 6-8 个五重层处饱和到体值。第一性原理计算也揭示了相同的依赖于层数的介电常数趋势。我们的介电响应结果普遍适用于层状二维半导体，预计对这个活跃的研究领域具有重要意义。
