Bahadursha Naresh, Bhavitha Sri Chanda, Ruthvik Kuna Krishna, Bhattacharya Swastik, Kanungo Sayan
Electrical and Electronics Engineering Department, Birla Institute of Technology and Science-Pilani, Hyderabad Campus, Hyderabad-500078, India.
Department of Physics, Birla Institute of Technology and Science-Pilani, Hyderabad Campus, Hyderabad, 500078, India.
Nanoscale. 2025 Jun 19;17(24):14781-14804. doi: 10.1039/d5nr00552c.
This study presents a comprehensive density functional theory-based investigation of the electronic properties of homogeneous bilayer Janus tin sulphide selenide (SnSSe) with different interfacial chalcogen pair configurations. This study focuses on interlayer band alignment, wherein the effects of interlayer distance modulation and applied biaxial strain are methodically studied. Next, the spatial distribution and lifetime of excitonic states are systematically analysed from the in-plane and inter-layer atomic orbital interactions, spatial separation of electron-hole wave functions, and spread of the conduction band in energy. Asymmetric interfacial chalcogen pairing exhibits a finite interlayer dipole moment and interlayer electric field. This reduces the energy bandgap and induces prominent type-2 band alignment between individual SnSSe layers, where band edge Bloch states are strongly localized in alternating layers. An increasing interlayer distance and applied biaxial tensile strain were found to retain the type-2 interlayer band alignment. In contrast, reducing the interlayer distance and biaxial compressive strain significantly altered interlayer atomic orbital interactions and annihilated the type-2 band alignment with a sharp reduction in the energy bandgap owing to the strong delocalization of band edge Bloch states. Thus, this study demonstrates the strain tuneable type-2 band alignment and interlayer excitonic properties of homogeneous bilayer SnSSe with broken interlayer mirror symmetry.
本研究基于密度泛函理论，对具有不同界面硫族元素对构型的均匀双层Janus硫化锡硒化物（SnSSe）的电子性质进行了全面研究。本研究聚焦于层间能带排列，其中系统地研究了层间距离调制和施加的双轴应变的影响。接下来，从面内和面间原子轨道相互作用、电子 - 空穴波函数的空间分离以及导带在能量上的展布等方面，系统地分析了激子态的空间分布和寿命。不对称的界面硫族元素配对表现出有限的层间偶极矩和层间电场。这降低了能带隙，并在各个SnSSe层之间诱导出显著的II型能带排列，其中带边布洛赫态强烈定域在交替的层中。发现增加层间距离和施加双轴拉伸应变可保持II型层间能带排列。相反，减小层间距离和双轴压缩应变会显著改变层间原子轨道相互作用，并消除II型能带排列，同时由于带边布洛赫态的强烈离域，能带隙急剧减小。因此，本研究证明了具有层间镜面对称性破坏的均匀双层SnSSe的应变可调II型能带排列和层间激子性质。
