Engineering of optical and electronic band gaps in transition metal dichalcogenide monolayers through external dielectric screening

Abstract

In order to fully exploit the potential of transition metal dichalcogenide monolayers (TMD-MLs), the well-controlled creation of atomically sharp lateral heterojunctions within these materials is highly desirable. A promising approach to create such heterojunctions is the local modulation of the electronic structure of an intrinsic TMD-ML via dielectric screening induced by its surrounding materials. For the realization of this non-invasive approach, an in-depth understanding of such dielectric effects is required. We report on the modulations of excitonic transitions in TMD-MLs through the effect of dielectric environments including low-k and high-k dielectric materials. We present absolute tuning ranges as large as 37 meV for the optical band gaps of WSe 2 and MoSe 2 MLs and relative tuning ranges on the order of 30% for the binding energies of neutral excitons in WSe 2 MLs. The findings suggest the possibility to reduce the electronic band gap of WSe 2 MLs by 120 meV, paving the way towards dielectrically defined lateral heterojunctions.

Radially polarized light beams from spin-forbidden dark excitons and trions in monolayer WSe2

“…The observed fine structure splitting of the bright negative trion confirms the high quality of our sample [31]. All measured energies agree well with previous reports on excitonic states in WSe 2 MLs encapsulated with h-BN [34,35,53,54]. Multiple broad emission lines appear at low energies but are excluded from the discussion in this work.…”

“…Electroluminescence in two-dimensional semiconductors has been be obtained in lateral p-n-junctions [57] or vertical van der Waals heterojunctions [58]. Further engineering of the optical properties of TMD-MLs and, hence, of a potential light source for radially polarized light can be achieved via dielectric engineering [54,59] or strain engineering [60][61][62][63].…”

Coulomb interaction in monolayer transition-metal dichalcogenides

“…Our calculations are focused on ML-MoSe 2 and ML-WSe 2 for which there are well-established results for the binding energies of trions in various ML configurations 41,43,58,[64][65][66][67][68][69][70] . When benchmarking the calculated values against empirical results, we focus on the trion binding energies and the energy difference between the 1s and 2s neutral-exciton states, ∆ 12 .…”

MoS2 and Perylene Derivative Based Type‐II Heterostructure: Bandgap Engineering and Giant Photoluminescence Enhancement

“…[15,44] The substrateinduced dielectric screening effect can strongly renormalize the quasi-particle (exciton, trion, etc.) [15,44] The substrateinduced dielectric screening effect can strongly renormalize the quasi-particle (exciton, trion, etc.)…”