Prediction of nonlayered oxide monolayers as flexible high-κ dielectrics with negative Poisson’s ratios
Yue Hu, Jingwen Jiang, Peng Zhang, Zhuang Ma, Fuxin Guan, Da Li, Zhengfang Qian, Xiuwen Zhang, Pu Huang
Abstract
Abstract During the last two decades, two-dimensional (2D) materials have been the focus of condensed matter physics and material science due to their promising fundamental properties and (opto-)electronic applications. However, high-κ 2D dielectrics that can be integrated within 2D devices are often missing. Here, we propose nonlayered oxide monolayers with calculated exfoliation energy as low as 0.39 J/m 2 stemming from the ionic feature of the metal oxide bonds. We predict 51 easily or potentially exfoliable oxide monolayers, including metals and insulators/semiconductors, with intriguing physical properties such as ultra-high κ values, negative Poisson’s ratios and large valley spin splitting. Among them, the most promising dielectric, GeO 2 , exhibits an auxetic effect, a κ value of 99, and forms type-I heterostructures with MoSe 2 and HfSe 2 , with a band offset of ~1 eV. Our study opens the way for designing nonlayered 2D oxides, offering a platform for studying the rich physics in ultra-thin oxides and their potential applications in future information technologies.