Indirect-To-Direct Band Gap Transition of One-Dimensional VSe: Theoretical Study with Dispersion Energy Correction.

Recently, we synthesized a one-dimensional (1D) structure of VSe. The 1D VSe resembles another 1D material, NbSe, which is expected to have a direct band gap. To determine the potential applications of this material, we calculated the band structures of 1D and bulk VSe using density functional theory by varying the number of chains and comparing their band structures and electronic properties with those of NbSe. The results showed that a small number of VSe chains have a direct band gap, whereas bulk VSe possesses an indirect band gap, like NbSe. We expect that VSe nanowires with diameters less than ∼20 Å would have direct band gaps. This indirect-to-direct band gap transition could lead to potential optoelectronic applications for this 1D material because materials with direct band gaps can absorb photons without being disturbed by phonons.