Manipulation of electronic and chemical properties of single layer MoS2: insights from ab initio calculations

DIPC Seminars

Talat S. Rahman, Univ. of Central Florida, USA
Donostia International Physics Center (DIPC). Paseo Manuel de Lardizabal, 4 (nearby the Facultad de Química), Donostia
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Manipulation of electronic and chemical properties of single layer MoS2: insights from ab initio calculations ** ** **Manipulation of electronic and chemical properties of single layer MoS 2: insights from _ab initio_ calculations** Talat S. Rahman Department of Physics, University of Central Florida, Orlando, FL 32816, USA Email: Single-layer Molybdenum disulfide (MoS2) appears to be a promising material for next generation applications because of its low-dimensionality and intrinsic direct band-gap of about 1.9 eV. Several experimental groups have reported novel electronic and transport properties. Efforts are underway to also grow the material on support (copper, silica, boron nitride, etc.). We have carried out density functional theory (DFT & TDDFT) based calculations, to provide a fundamental understanding of some of the characteristics of this material. In this talk I will show how our calculations have helped identify the geometric and electronic structure of a reactive phase (Mo2S3) of MoSx when grown on Cu(111) [1], while also providing qualitative and quantitative agreement to the Moiré pattern of MoS2 on Cu(111) observed in STM measurements [2]. To examine the effect of defects, I will present results for a single-layer MoS2 with sulfur vacancies which shows the emergence of defect states in the band-gap. This state is unoccupied and localized at the vacancy row. I will consider possible vacancy configurations which may provide a route for alcohol synthesis from syngas (CO, H2, CO2) from single layer MoS2. Tuning of the band gap through alloying with Se or hydrogenation will also be presented. In the same vain, we find that mirror joined-edge defects formed between two MoS2 domains exhibit metallic behavior. More interestingly, we find signatures of magnetism at specific joined-edge defects formed between two sulfur edges with 0% sulfur coverage. The binding energies of exciton and trion present in single-layer MoS2 obtained will be discussed, together with the implications of the above findings to ongoing experiments in several labs. [1] D. Sun, et al., Angew. Chem. Int. Ed. 51, 10284 (2012). [2] D. Le, L. Bartels, and T. S. Rahman, Phys. Rev. B 85, 075429 (2012).