Tunable band gaps and optical absorption properties of bent MoS2 nanoribbons

Abstract

The large tunability of band gaps and optical absorptions of armchair MoS2 nanoribbons of different widths under bending is studied using density functional theory and many-body perturbation GW and Bethe–Salpeter equation approaches. We find that there are three critical bending curvatures, and the non-edge and edge band gaps generally show a non-monotonic trend with bending. The non-degenerate edge gap splits show an oscillating feature with ribbon width n, with a period $$\Delta n=3$$ Δ n = 3 , due to quantum confinement effects. The complex strain patterns on the bent nanoribbons control the varying features of band structures and band gaps that result in varying exciton formations and optical properties. The binding energy and the spin singlet–triplet split of the exciton forming the lowest absorption peak generally decrease with bending curvatures. The large tunability of optical properties of bent MoS2 nanoribbons is promising and will find applications in tunable optoelectronic nanodevices.

Spin-polarization anisotropy controlled by bending in tungsten diselenide nanoribbons and tunable excitonic states

“…The EG gap of A13WSe 2 shows a general decrease with κ , while within 0.071 Å −1 < κ < 0.125 Å −1 (or 8 Å < R < 14 Å) it shows a relatively flat or a slight hump feature, in line with the EG changing trend with κ of the armchair MoS 2 nanoribbons in a previous study. 23 Due to the indirect EG of A12WSe 2 within 0.077 Å −1 < κ < 0.10 Å −1 (or 10 Å < R < 13 Å), the EG gap of A12WSe 2 shows a relatively large value and forms a peak within 0.071 Å −1 < κ < 0.11 Å −1 . The EG and NEG gaps of A7WSe 2 show a less varying feature with κ , as shown in Fig.…”

“…Nanoribbons are interesting, reduced forms of 2D layered materials. [18][19][20][21][22][23][24][25][26] Compared with their 2D counterparts, they have more spatial confinement effects and rich edge states, making Department of Physics, Temple University, Philadelphia, PA 19122, USA. E-mail: hongtang@temple.edu † Electronic supplementary information (ESI) available: Technical note 1 for spinpolarization anisotropy analyses for A12WSe 2 and A7WSe 2 nanoribbons, note 2 for the d-orbital decomposition analyses for A13WSe 2 , Table S1 for the five observations to the band structure map of the d-orbital decomposition of the spin-polarization along the x and y axes for the A13WSe 2 nanoribbon under different bending conditions, note 3 for the k-grid convergence test of the optical absorption spectrum, Fig.…”

“…Nanoribbons are interesting, reduced forms of 2D layered materials. 18–26 Compared with their 2D counterparts, they have more spatial confinement effects and rich edge states, making them rife of new functionalities and attractive for applications in compact nanoelectronics, magnetic, optoelectronic, and band-topology based electronic and quantum information devices. 18,19 MoS 2 zigzag nanoribbons were calculated as metallic and with ferromagnetic edges.…”

“…19 Tang et al 21 showed that the direction of magnetization in CrI 3 nanoribbons can be stably aligned both out-of-plane and parallel to the ribbon axis, increasing their operating controllability. Also, the rich exciton states are shown in SiC, 22 MoS 2 , 23 black phosphorene, 24 and CrI 3 nanoribbons, 21 and the exciton states can be tuned by bending or strains in the nanoribbons.…”

Density Functional Theory Study of Controllable Optical Absorptions and Magneto-Optical Properties of Magnetic CrI3 Nanoribbons: Implications for Compact 2D Magnetic Devices

“…Both Jiang et al and Wang et al calculated the magnetic properties of CrI 3 nanoribbons and confirmed that FM is the stable state for CrI 3 nanoribbons, and the edge states dominate the band structures around the Fermi level. By applying uniaxial strains or bending, one can create local strains on the nanoribbons and effectively modify the edge states and band structures, − leading to controllable electronic and optical properties. In this work, we investigate tensile strains and bending-induced tunability of electronic structures of the magnetic CrI 3 nanoribbons.…”