Longuinhos R, Late Dattatray J, Viana B C, Alencar R S, Terrones M, Souza Filho A G, Jorio A, Ribeiro-Soares J
Departamento de Física, Universidade Federal de Lavras, Lavras, Minas Gerais, 37200-000, Brazil.
Departamento de Física, Universidade Federal do Piauí, Teresina, Piauí, 64049-550, Brazil.
Phys Chem Chem Phys. 2024 Nov 7;26(43):27260-27269. doi: 10.1039/d4cp02695k.
Gallium sulfide (GaS) stands out as a versatile nonlinear optical material for green-blue optoelectronic and photocatalytic nano-devices. In addition, the in-plane breaking strain and mechanical strength of layered GaS make it a promising candidate for next-generation flexible nanodevices. The fast and reliable assessment of the number of layers, without sample loss, is key for these applications. Here we unveil the influence of dimensionality in the structural, mechanical, and vibrational properties of GaS by applying density-functional theory-based quantum-simulations and group-theory analysis. We find its intralayer structure and interlayer distances are essentially independent of the number of layers, in agreement with the van der Waals forces as dominant interlayer interactions. The translational symmetry breaking along the stacking direction results in different structural symmetries for monolayers, -odd layers, -even layers, and bulk geometries. Its force constants against rigid-layer shear, = 1.35 × 10 N m, and breathing, = 5.00 × 10 N m, displacements remain the same from bulk to bilayer structures. The related stiffness coefficients in bulk are = 10.2 GPa and = 37.7 GPa, respectively. This insight into GaS interlayer interactions and elastic coefficients reveals it as a promising lubricant for nano-mechanic applications and it is easy to cleave for thickness engineering, even in comparison with layered graphite, MoS and other transition metal dichalcogenides and group-IIIA metal monochalcogenides. We present the GaS Raman and infrared spectra dependence on the layer number as strategies for sample thickness characterization and derive formulas for distinguishing the number of layers in both high and low-frequency regimes. In addition, our analysis of their optical-activity selection rules and polarization dependencies is applicable to isostructural group-IIIA metal monochalcogenides with 2H-layer stacking, such as gallium/indium sulphide/selenide. These results contribute to rapid and non-destructive characterization of the material's structure, which is of paramount importance for the manufacturing of devices and the utilization of its diverse properties.
硫化镓（GaS）作为一种用于绿蓝光光电子和光催化纳米器件的多功能非线性光学材料脱颖而出。此外，层状GaS的面内断裂应变和机械强度使其成为下一代柔性纳米器件的有前途的候选材料。在不损失样品的情况下快速可靠地评估层数是这些应用的关键。在这里，我们通过应用基于密度泛函理论的量子模拟和群论分析，揭示了维度对GaS的结构、机械和振动特性的影响。我们发现其层内结构和层间距离基本上与层数无关，这与范德华力作为主要层间相互作用一致。沿堆叠方向的平移对称性破坏导致单层、奇数层、偶数层和体几何结构具有不同的结构对称性。其抵抗刚性层剪切的力常数(C_{6}=1.35×10) (N m)，以及抵抗呼吸位移的力常数(C_{11}=5.00×10) (N m)，从体结构到双层结构保持不变。体结构中的相关刚度系数分别为(C_{6}=10.2) (GPa)和(C_{11}=37.7) (GPa)。对GaS层间相互作用和弹性系数的这种深入了解表明，它是纳米机械应用中有前途的润滑剂，并且即使与层状石墨、MoS₂以及其他过渡金属二硫属化物和IIIA族金属单硫属化物相比，也易于进行厚度工程的劈裂。我们展示了GaS拉曼光谱和红外光谱对层数的依赖性，作为样品厚度表征的策略，并推导了在高频和低频区域区分层数的公式。此外，我们对其光学活性选择规则和偏振依赖性的分析适用于具有2H层堆叠的同构IIIA族金属单硫属化物，如硫化镓/铟/硒。这些结果有助于对材料结构进行快速无损表征，这对于器件制造及其各种性能的利用至关重要。
