Electric Field-Tunable Structural Phase Transitions in Monolayer Tellurium.

Electronic properties of monolayer tellurium (Te) with three proposed atomic configurations under external electric field were investigated through first-principles calculations. The calculated results demonstrate that α-Te and γ-Te have indirect band gaps, whereas ß-Te, when no electric field is applied, can be considered as a direct semiconductor. An interesting structural change occurs in α- and γ-phase Te under a specific electric field strength, as does a change in structural chirality. In the presence of a perpendicular electric field, the band gaps can be modified and drawn close to 0 eV at a certain critical electric field strength. Before that, the band gaps of α-Te and γ-Te are nearly constant, while that of ß-Te shows a quadratic relationship to electric field strength. These findings not only enrich our understanding of the electronic properties of monolayer tellurium but also show that monolayer tellurium has tremendous potential in nanoscale electronic devices owing to its tunable band gaps.

A first-principles study of strain tuned optical properties in monolayer tellurium.

First-principles calculations are employed to study the optical properties of monolayer Te tuned by biaxial strain. Our results demonstrate that monolayer Te has strong absorption in the visible and ultraviolet regions, and that a structural transition occurs between the α-phase and the ß-phase under certain strain. In addition, there is significant optical anisotropy in α- and ß-Te, while γ-Te shows isotropic characteristics due to their different structural properties. Furthermore, strain has a significant impact on the optical properties. With increasing strain, the real and imaginary parts of the dielectric function exhibit redshift. In addition, the absorption spectrum is more likely to be excited under compressive strain rather than tensile strain in α- and ß-Te, while only slight differences are induced in γ-Te. These findings can not only enhance the understanding of two-dimensional tellurium, but also provide an effective way to tune the optical properties for potential application in optoelectronic devices.