Yang Mingjun, Shu Haibo, Tang Pengtao, Liang Pei, Cao Dan, Chen Xiaoshuang
College of Optical and Electronic Technology, China Jiliang University, 310018 Hangzhou, China.
College of Science, China Jiliang University, 310018 Hangzhou, China.
ACS Appl Mater Interfaces. 2021 Feb 24;13(7):8764-8773. doi: 10.1021/acsami.0c21532. Epub 2021 Feb 8.
Two-dimensional (2D) ferromagnetic (FM) semiconductors with a high Curie temperature and tunable electronic properties are a long-term pursuing target for the development of high-performance spin-dependent optoelectronic devices. Herein, on the basis of density functional theory calculations, we report a new strategy to tune the Curie temperature and electronic structures of a ferromagnetic CrBr monolayer through the formation of CrBr/GaN van der Waals heterostructures. Our calculated results demonstrate that the Curie temperature and band alignment of CrBr/GaN heterostructures strongly depend on the thickness and polarization direction of the GaN layer. The combination of the CrBr monolayer with N-terminated GaN nanosheets leads to enhanced FM coupling via superexchange interactions between the Cr- and Cr-e orbitals, consequently resulting in a Curie temperature of CrBr of up to 67 K. Moreover, self-doped p-n junctions can be naturally formed in the heterostructures without additional modulation of external fields. The enhanced FM coupling and self-doping effect in the heterostructures are associated with the intrinsic polarization of the GaN layer that drives interfacial electron transfers from GaN to CrBr. Therefore, this work not only offers an efficient scheme to boost the Curie temperature of the CrBr monolayer but also opens up a new route to realize nonvolatile van der Waals p-n junctions.
具有高居里温度和可调节电子特性的二维（2D）铁磁（FM）半导体是高性能自旋相关光电器件发展的长期追求目标。在此，基于密度泛函理论计算，我们报告了一种通过形成CrBr/GaN范德华异质结构来调节铁磁CrBr单层居里温度和电子结构的新策略。我们的计算结果表明，CrBr/GaN异质结构的居里温度和能带排列强烈依赖于GaN层的厚度和极化方向。CrBr单层与N端GaN纳米片的结合通过Cr和Cr-e轨道之间的超交换相互作用增强了FM耦合，从而使CrBr的居里温度高达67 K。此外，在异质结构中可以自然形成自掺杂的p-n结，而无需额外的外部场调制。异质结构中增强的FM耦合和自掺杂效应与GaN层的固有极化有关，该极化驱动界面电子从GaN转移到CrBr。因此，这项工作不仅提供了一种提高CrBr单层居里温度的有效方案，而且开辟了一条实现非易失性范德华p-n结的新途径。
