Programme

P.7 -- Poster

Date: Friday, 24 November 2017

Time: 10:30 - 11:20

First-Principles Study of Electronic and Optical Properties of Alkali Metal Intercalated Transition Metal Dichalcogenides

Thanundon Kongnok (1), Sukit Limpijumnong (1,2,3) and Sirichok Jungthawan (1,2)

(1) School of Physics, Institute of Science, and NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand; (2) Thailand Center of Excellence in Physics (ThEP), Commission on Higher Education, Bangkok 10400, Thailand; (3) Synchrotron Light Research Institute, Nakhon Ratchasima 30000, Thailand

MoS2 is a compound in transition metal dichalcogenide (TMDC) family that is semiconductor with layered honeycomb structure having strong in-plane bonding and weak out-of-plane van der Waals interactions. In the bulk form, MoS2 has an indirect band gap, whereas monolayer form has direct band gap which is more suitable for device applications. It has been proposed that the electronic characteristic of the monolayer can be reproduced experimentally in MoS2 by K intercalation [1]. In this work, the effects of alkali metal (such as Li, Na, K, and Rb) intercalation are investigated by using first-principles calculations in the 2×2×1 supercell. The electronic structures from supercell calculations are unfolded [2] onto the high symmetry paths as defined in the first Brillouin zone of the primitive cell. The results show significant expansion of interlayer spacing and contribution of electron donation from alkali metal to the conduction band of MoS2. The expansion obviously depends on atomic radii of the intercalated metals. Moreover, band gap type is changed from indirect to direct because the expansion of the interlayer spacing reduces the electronic interactions between adjacent layers creating a quasi-monolayer character. It has been found that the interlayer spacing of MoS2K0.25 and MoS2Rb0.25 are large enough to exhibit quasi-monolayer character. Furthermore, the effects of concentration of alkali metal have been investigated by varying concentration of K. We found that in-plane lattice constant increases proportional to the concentration. Our results suggest that different atomic radii and concentration of intercalated alkali metals could provide an opportunity to tune electronic structures of TMDC materials. References [1] Eknapakul, T., et al., Electronic structure of a quasi-freestanding MoS2 monolayer. 2014. Nano Lett 14(3): 1312-6. [2] Tomić, M., H.O. Jeschke, and R. Valentí, Unfolding of electronic structure through induced representations of space groups: Application to Fe-based superconductors. 2014. Physical Review B, 90(19): 195121.

Presenter: Thanundon Kongnok