空位缺陷对单层2H-MoTe_(2)光电效应的第一性原理研究

First-Principles Study on Photogalvanic Effect of Vacancy Defects on Monolayer 2H-MoTe_(2)

MoTe_(2)由于其类石墨烯的堆叠方式和丰富的相结构而引起科研人员的广泛研究,特别是合适的禁带宽度使其在光电器件领域有着光明的应用前景。基于非平衡格林函数-密度泛函理论,通过第一性原理计算方法,研究了不同原子空位缺陷对单层2H-MoTe_(2)光电效应的影响。结果表明:不同空位缺陷下2H-MoTe_(2)器件的光电流函数与唯象理论相符合。光子能量在1.0~2.8 eV时,2Te空位缺陷对单层2H-MoTe_(2)的光电流有显著提升,特别是在光子能量2.6 eV时获得所有器件的最大光电流。利用能带结构发现不同原子空位缺陷都导致单层2H-MoTe_(2)的价带向高能级处偏移,而导带向低能级处偏移,减小了带隙,在线性偏振光的照射下有利于电子从价带跃迁到导带形成光电流。同时发现1Te空位缺陷和Mo空位缺陷的单层2H-MoTe_(2)在远离费米能级处具有相似的能带结构,从而导致在光子能量大于1.6 eV时,1Te空位和Mo空位器件的光电流随光子能量的变化拥有相同的变化趋势。这些计算结果可以用于指导MoTe_(2)光电器件的设计。

MoTe_(2)has been widely studied due to its special stacking mode and rich phase structure, especially the suitable band gap which makes it have a promising application in the field of optoelectronic devices. Based on the non-equilibrium Green’s function-density functional theory, the influence of different atomic vacancy defects on the photogalvanic effect of monolayer 2H-MoTe_(2)was studied by the first-principles calculation method. The results show that the photocurrent function of 2H-MoTe_(2)devices with different vacancies is consistent with the phenomenological theory. In the photon energy range from 1.0 eV to 2.8 eV, 2Te vacancy significantly improves the photocurrent of 2H-MoTe_(2), especially when the photon energy is 2.6 eV, the maximum photocurrent of all devices is obtained. With the energy band structure, it is found that different atomic vacancy defects lead to the shift of the valence band to the high energy level and the conduction band to the low energy level, which reduces the band gap between the four devices and conducive to the transition of electrons from the valence band to the conduction band to form photocurrent under the irradiation of linearly polarized light. It is found that the monolayer 2H-MoTe_(2)of 1Te vacancy and Mo vacancy has a similar energy band structure far away from the Fermi level, which leads to the same change trend of the device photocurrent when the photon energy is greater than 1.6 eV. These results can be used to guide the design of MoTe_(2)optoelectronic devices.