Jeon Dohyeon, Kang Yebin, Kim Taekyeong
Department of Physics, Hankuk University of Foreign Studies, 81 Oedae-ro, Mohyeon-myeon Cheoin-gu, Yongin-si 17035, Republic of Korea.
J Phys Chem Lett. 2020 Aug 20;11(16):6684-6690. doi: 10.1021/acs.jpclett.0c01521. Epub 2020 Aug 6.
We investigate the layer-number-dependent dielectric response of WSe by measuring the phase shift (Φ) through an electrostatic force microscopy (EFM). The measured Φ results stem mainly from the capacitive coupling between the tip and WSe based on the plane capacitor model, leading to changes in the second derivative of the capacitance ('') values, which increase in a few layers and saturate to the bulk value under an applied EFM tip bias. The '' value is related to the dielectric polarization, reflecting the charge carrier concentration and mobility of WSe flakes with different numbers of layers. This implies that the dielectric constant of WSe shows layer-number-dependent behavior which increases with the number of layers, approaching the bulk value. Furthermore, we also construct a spatially resolved '' map to observe the local dielectric response of WSe flakes. Our work could be significant in that it can improve the performance of novel electronic devices based on the controllable dielectric properties of 2D vdW semiconductor materials.
我们通过使用静电力显微镜（EFM）测量相移（Φ）来研究WSe层数依赖的介电响应。所测量的Φ结果主要源于基于平面电容器模型的针尖与WSe之间的电容耦合，导致电容二阶导数（''）值发生变化。在施加的EFM针尖偏压下，该值在几层时增加并饱和至体材料值。''值与介电极化相关，反映了不同层数WSe薄片的载流子浓度和迁移率。这意味着WSe的介电常数呈现出随层数增加而增加并趋近于体材料值的层数依赖行为。此外，我们还构建了空间分辨的''图以观察WSe薄片的局部介电响应。我们的工作可能具有重要意义，因为它可以基于二维范德华半导体材料可控的介电特性来提高新型电子器件的性能。
