Bending deformation modulation of the optoelectronic properties of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, O): a first-principles study

A first-principles approach based on density functional theory was used to explore the effect of bending deformation on the electrical structure of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, and O). The study included alternate doping of nonmetallic atoms, as well as a comparison of the effects of intrinsic bending deformation and nonmetallic doping deformation. The results demonstrate that boron atom doping raises the Fermi energy level. Examining the energy band structure indicates that the intrinsic molybdenum ditelluride is a direct band gap semiconductor, which is transformed from a direct band gap to an indirect band gap after doping. We selected boron-doped systems for bending deformation and compared them with the intrinsic systems. With increasing deformation, all systems start to shift from semiconductor to metal. When the deformation reaches 8°, the energy levels fill and the electron energy increases. The intrinsically bent systems transition from direct band gap to indirect band gap and eventually to metal. The indirect band gap semiconductor-to-metal transition process occurs after the bending deformation of the boron-doped atoms. The analytical results show that the absorption and reflection peaks of the molybdenum ditelluride system are blue-shifted after the bending deformation of the boron-doped atoms.

Under fundamental principles, this research depends on the density functional theory framework (DFT) using the CASTEP module in the Materials-Studio software. The plane-wave pseudopotential approach with modified gradient approximation and the Perdew-Burke-Ernzerhof (PBE) generalized function is used for structure optimization and total energy calculations of the X-doped (X = B, C, N, O) MoTe₂ system at different shape variables. Geometry optimization of the 27-atom superlattice MoTe₂ was carried out, followed by alternative doping of tellurium atoms in the molybdenum ditelluride with B, C, N, and O. In this paper, the intrinsic bending deformation and B-doping of molybdenum ditelluride were selected for deformation analysis. Intrinsic bending deformations and boron-doped molybdenum ditelluride with bending angles ranging from 2° to 8° were employed for deformation investigation. In Fig. 1, pink is used to represent doped B atoms, orange is used to describe Te atoms, and green is used to represent Mo atoms. For the degree of deformation of molybdenum ditelluride, in this paper, it is expressed by the bending angle, i.e., the angle of the plane of molybdenum ditelluride after bending and deformation of a single layer of molybdenum ditelluride concerning the angle of the plane folded for the deformed plane. How to do it: For ease of presentation, the atomic chains are set to different colors. The purple part on both sides of the figure is bent and deformed, 3–5 atoms are fixed appropriately, and the middle part is deformed. On this basis, the bending deformation of intrinsically doped and boron-doped MoTe₂ is comparatively analyzed. The effect of boron-doped atoms on the structure of MoTe₂ is systematically investigated to study its structural stability and electronic structure.