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|Title:||THE EFFECT OF SUBSTRATE ON THE ELECTRONIC AND OPTICAL PROPERTIES OF MONOLAYER TRANSITION METAL DICHALCOGENIDES MX2 (M=Mo, W; X=S, Se, Te)||Authors:||XU LEI||Keywords:||first-principles, 2D material, substrate, valley, Berry curvature, exciton||Issue Date:||10-Aug-2018||Citation:||XU LEI (2018-08-10). THE EFFECT OF SUBSTRATE ON THE ELECTRONIC AND OPTICAL PROPERTIES OF MONOLAYER TRANSITION METAL DICHALCOGENIDES MX2 (M=Mo, W; X=S, Se, Te). ScholarBank@NUS Repository.||Abstract:||Monolayer group-VIB transition metal dichalcogenides (TMDs) are direct band gap semiconductors, where two valleys are formed at K and K' points. The realization of valley polarization is an essential step for manipulation of valley pseudospin. In this thesis, we first demonstrate that valley degeneracy in monolayer TMDs can be lifted by proximity coupling to an insulating magnetic substrate. Owing to valley contrasting Berry curvature and time-reversal symmetry breaking, a spin- and valley- polarized anomalous Hall current can be generated under an in-plane electric field. On the other hand, the large exciton binding energy resulted from the reduced dielectric screening in monolayer TMDs are unfavourable for optoelectronic applications. Based on first-principles and numerical calculations, we find that the presence of a dielectric substrate can greatly accelerate the field-assisted exciton dissociation process. Therefore, our work suggests that the performance of 2D material based device can be significantly improved by substrate engineering.||URI:||http://scholarbank.nus.edu.sg/handle/10635/149783|
|Appears in Collections:||Ph.D Theses (Open)|
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