Flexible and Anisotropic Properties of Monolayer MX₂ (M = Tc and Re; X = S, Se)

Abstract

Flexible and anisotropic response of layered transition metal dichalcogenides MX2 (M = Tc and Re; X = S, Se) is important for wearable and polarized optoelectronics. Herein, the elastic, electronic, and optical dielectric properties of these two-dimensional (2D) materials have been investigated by density functional theory (DFT) with different van der Waals correction and Heyd–Scuseria–Ernzerhof hybrid functional. The Young’s modulus of these materials is low, which indicates that they are favorable for the flexible optoelectronic devices. The band gaps fall in between 1.70 and 2.12 eV with the d states of transition metal atoms playing an important role in conduction and valence bands. In addition, the appearance of band nesting implies that there are strong light–matter interactions in these materials, indicating they are suitable for photovoltaic and photocatalytic applications. Unlike the traditional 2D materials such as MoS2, the optical dielectric properties manifest highly in-plane anisotropic in the infrared and visible region, which is suitable for on-chip polarization manipulation with these materials. This work promotes the understanding of flexible and anisotropic response of these materials and their potential applications in new types of optoelectronic devices.