Structural, electronic and optical properties of strained CdS monolayer and bilayer structures are studied to examine the possibility of controlling their properties for application in the field of nano-devices. First-principles density functional theory (DFT) calculations are done as implemented in SIESTA code that uses a pseudopotential and a numerical nano-orbital basis set. Exchange correlation energies were described using the general gradient approximation (GGA) in the form of Perdew–Burke–Ernzerhof (PBE) functional. We have found that the electronic band structure of monolayer and bilayer CdS is quite sensitive to biaxial strain, and as a result bandgap energy can be tuned over a wide range with compressive and tensile strains. While both the monolayer and bilayer structures maintain the direct bandgap nature of the relaxed structure even under compressive strain, tensile strain transforms the material into indirect gap semiconductors with degenerate electronic band structure. It is found that effective masses can also be controlled with biaxial strain, and hence carrier mobility can be improved in the process. Our DFT calculations also predict that in addition to tuning the optical absorption, intensity of direct bandgap absorption in these two structures can be enhanced under tensile strain.

研究了应变 CdS 单层和双层结构的结构、电子和光学特性，以检查控制它们在纳米器件领域应用的特性的可能性。第一性原理密度泛函理论 (DFT) 计算在 SIESTA 代码中实现，该代码使用赝势和数值纳米轨道基组。使用 Perdew-Burke-Ernzerhof (PBE) 泛函形式的一般梯度近似 (GGA) 描述了交换相关能。我们发现单层和双层 CdS 的电子能带结构对双轴应变非常敏感，因此可以在压缩和拉伸应变的宽范围内调节带隙能量。虽然单层和双层结构即使在压缩应变下也保持松弛结构的直接带隙性质，但拉伸应变将材料转变为具有简并电子带结构的间接带隙半导体。发现有效质量也可以通过双轴应变来控制，因此在此过程中可以提高载流子迁移率。我们的 DFT 计算还预测，除了调整光吸收外，这两种结构中的直接带隙吸收强度在拉伸应变下也可以增强。