Fig. 4: Optical gap from interlayer excitons in TMDC vdWH.
From: Bandgap engineering of two-dimensional semiconductor materials
a Microscope image of a MoSe2/WSe2 van der Waals heterostructure. b PL spectrum (at T = 20 K) of the sample shown in (a)69. The inset sketches intralayer (red and green) excitons in the Mo(W)Se2 layer, associated with the features labeled as X\({}_{Mo(W)}^{0}\) in the PL spectrum, and the interlayer (yellow) exciton, associated with the XIL peak. X\({}_{Mo(W)}^{-}\) refers to intralayer trions. c Top panels: band structures of single-layer MoS2 (green) and WS2 (red) superimposed, and band structure of a MoS2/WS2 heterostructure. Colors in the latter represent probability-density projections in each material. Bottom panels: the same as top, but for GeS (green) and SiTe (red) layers in the buckled form. d Survey of intralayer (triangles) and IL (circles) exciton peaks, experimentally observed in PL measurements of different combinations of TMDC as vdWH. Background colors delimit the range of energies observed for exciton absorption in single-layer experiments with MoS2 (green), MoSe2 (red), WS2 (blue), and WSe2 (yellow)69,75,76,77,78,79,80,81,82,83,84,85,86,87. Colors of triangles are chosen as to match those corresponding to each material involved in the observed intralayer exciton peak. Panels a, b reprinted by permission from Springer Nature Nature Communications69, Copyright (2015), advance online publication, 24th February 2015 (https://doi.org/10.1038/ncomms7242 Nat.Commun).
