Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
Phys Chem Chem Phys. 2018 Jun 20;20(24):16604-16614. doi: 10.1039/c8cp02995d.
The physical and chemical properties of monolayers can be tuned by selective combinations so as to be useful for device applications. Here we present a density functional theory study on the structural, electronic and optical properties of three transition metal dichalcogenide (TMD) heterobilayers, ZrS2/HfS2, ZrSe2/HfSe2 and SnS2/SnSe2. These heterobilayers are predicted to be energetically and dynamically stable structures. The band structure calculation result shows that ZrS2/HfS2, ZrSe2/HfSe2 and SnS2/SnSe2 heterobilayers are semiconductors with indirect band gaps. The efficient charge carrier separation in ZrS2/HfS2 and ZrSe2/HfSe2 heterobilayers indicates that they can be employed in energy harvesting devices. Contrary to the previous report on the ZrS2/HfS2 heterobilayer, we found it to have an intrinsic type-II band alignment which is required in p-n junction diodes and tunnel field effect transistors, and the same behavior was observed in ZrSe2/HfSe2 and SnS2/SnSe2 for the first time. The ZrS2/HfS2 and ZrSe2/HfSe2 heterobilayers reveal enhanced optical absorption both in the ultraviolet and visible regions as compared to their respective monolayers, whereas the parallel and perpendicular part of the optical absorption of the SnS2/SnSe2 heterobilayer revealed an anisotropic behavior; the perpendicular part is largely improved in the higher energy region, and the parallel part of the optical absorption is improved in the ultraviolet region.
通过有选择性的组合，可以调整单层的物理和化学性质，使其适用于器件应用。在这里，我们通过密度泛函理论研究了三种过渡金属二卤化物（TMD）异质双层结构ZrS2/HfS2、ZrSe2/HfSe2 和 SnS2/SnSe2 的结构、电子和光学性质。这些异质双层结构被预测为能量和动力学稳定的结构。能带结构计算结果表明，ZrS2/HfS2、ZrSe2/HfSe2 和 SnS2/SnSe2 异质双层结构是具有间接带隙的半导体。ZrS2/HfS2 和 ZrSe2/HfSe2 异质双层结构中有效的电荷载流子分离表明它们可以用于能量收集器件。与之前关于 ZrS2/HfS2 异质双层结构的报告相反，我们发现它具有本征的 II 型能带排列，这是 p-n 结二极管和隧道场效应晶体管所需要的，在 ZrSe2/HfSe2 和 SnS2/SnSe2 中也首次观察到了同样的行为。与各自的单层相比，ZrS2/HfS2 和 ZrSe2/HfSe2 异质双层结构在紫外和可见光区都表现出增强的光吸收，而 SnS2/SnSe2 异质双层结构的光吸收的平行和垂直部分表现出各向异性；垂直部分在高能区有很大的提高，而紫外区的光吸收平行部分有所提高。
