Lin Yu-Hsiu, Comaskey William P, Mendoza-Cortes Jose L
Department of Chemical Engineering and Materials Science, Michigan State University East Lansing MI 48824 USA
Department of Health Physics, University of Nevada Las Vegas NV 89154 USA.
Nanoscale Adv. 2025 Feb 13;7(7):2047-2056. doi: 10.1039/d5na00112a. eCollection 2025 Mar 25.
Layered two-dimensional (2D) materials exhibit unique properties not found in their individual forms, opening new avenues for material exploration. This study examines MX transition metal dichalcogenides (TMDCs), where M is Mo or W, and X is S, Se or Te. These materials are foundational for the creation of hetero- and homo-bilayers with various stacking configurations. Recent interest has focused on twisted homogeneous bilayers, as critical twist angles can significantly alter material properties. This work highlights MX TMDC bilayers with twisted angles that form Moiré patterns, essential to understanding the behaviors of these materials. We performed first-principles calculations using Density Functional Theory (DFT) with range-separated hybrid functionals on 30 combinations of six MX materials with two stacking configurations, revealing that the building blocks and stacking arrangements influence the stability of the heterostructure and the band gap energy ( ). In particular, the MoTe/WSe heterostructure, shifted by 60°, exhibits a direct band gap, indicating potential for novel applications. Our investigation of homobilayers included fully relaxed and low-strain scenarios, examining various stacking styles and twisting angles. Under low-strain conditions, MoS, WS, and WSe can exhibit direct or indirect band gaps at specific twist angles. Additionally, MoS can transition between semiconductor and conductor states, showcasing diverse electronic properties. Critical twist angles, specifically 17.9° and its corresponding angles (42.1°, 77.9° and 102.1°), in twisted WS and WSe bilayers create symmetric Moiré patterns, leading to direct band gaps. The magnitude of the band gap energy can be tuned by varying the twist angles, which also affect the flatness of the electronic band. Like conventional stacking, most twisted TMDC bilayers exhibit favorable interlayer interactions but with more tailorable characteristics. Using heterostructures and controlled twist angles is a powerful approach in material engineering, enabling the manipulation of various electronic behaviors in advanced materials.
层状二维（2D）材料展现出其单一形式所没有的独特性质，为材料探索开辟了新途径。本研究考察了MX过渡金属二硫属化物（TMDCs），其中M为Mo或W，X为S、Se或Te。这些材料是创建具有各种堆叠构型的异质和同质双层的基础。最近的研究兴趣集中在扭曲的同质双层上，因为关键的扭曲角度会显著改变材料性质。这项工作突出了具有形成莫尔图案的扭曲角度的MX TMDC双层，这对于理解这些材料的行为至关重要。我们使用密度泛函理论（DFT）和范围分离混合泛函对六种MX材料的30种组合以及两种堆叠构型进行了第一性原理计算，结果表明结构单元和堆叠排列会影响异质结构的稳定性和带隙能量（ ）。特别是，MoTe/WSe异质结构在60°位移时呈现直接带隙，显示出新型应用的潜力。我们对同质双层的研究包括完全弛豫和低应变情况，考察了各种堆叠方式和扭曲角度。在低应变条件下，MoS、WS和WSe在特定扭曲角度下可呈现直接或间接带隙。此外，MoS可在半导体和导体状态之间转变，展现出多样的电子性质。扭曲的WS和WSe双层中的关键扭曲角度，特别是17.9°及其对应角度（42.1°、77.9°和102.1°）会产生对称的莫尔图案，从而导致直接带隙。带隙能量的大小可通过改变扭曲角度进行调节，这也会影响电子能带的平坦度。与传统堆叠一样，大多数扭曲的TMDC双层表现出有利的层间相互作用，但具有更可定制的特性。使用异质结构和可控的扭曲角度是材料工程中的一种强大方法，能够操控先进材料中的各种电子行为。
