Extended Data Fig. 6: Variation of photoluminescence and reflectance contrast spectra in MoSe2/WS2 heterobilayers fabricated from exfoliated MoSe2 and WS2 monolayers encapsulated in hBN.
From: Resonantly hybridized excitons in moiré superlattices in van der Waals heterostructures
a, Bright-field image of a fully encapsulated MoSe2/WS2 sample S1; the points for which we report the photoluminescence and reflectance contrast spectra in b–d are marked. Scale bar, 10 μm. b–d, Low-temperature photoluminescence (black) and reflectance contrast (red) spectra recorded in several regions of the sample marked in a. The two higher-energy peaks in the photoluminescence spectra, X∗ at 1.624 and XA at 1.652 eV, correspond to trion and excition emission unintentionally collected from the single-layer MoSe2 area located at the right side of the heterobilayer region. The position of these peaks remains unchanged in all three points, while their intensity decreases gradually with the increasing spatial separation. The two lower-energy photoluminescence peaks, labelled hX∗ and hX1, represent the emission originating in the heterostructure region and show variation in position and relative intensities across the heterostructure region, probably caused by the non-uniform strain and doping. The reflectance contrast spectra recorded at the three points are similar, with the two lower-energy peaks directly corresponding to hX∗ and hX1 in the photoluminescence spectra, and hX2 and hX3 representing the higher-energy states. e, Comparison of low-temperature photoluminescence spectra recorded in the samples fabricated from mechanically exfoliated monolayers. Dashed lines show photoluminescence spectra of uncoupled single-layer MoSe2, recorded in the same sample, in which an uncoupled MoSe2 monolayer area was present. Samples S1–S4 were fabricated with the crystal axes of the two materials closely aligned, whereas sample S5 was made with a considerable rotational misalignment (θ = 12°). Despite the variation of exciton (XA) and trion (X∗) energies, all four aligned samples show a hybridized exciton peak hX1, located 20–30 meV lower in energy than the monolayer trion line. Samples S1 and S2 show an additional lower-energy line hX∗ positioned approximately 32 meV lower in energy than hX1. Figure 4 reports data for the closely aligned sample S1 and the misaligned sample S5. Figure 5 reports data for sample S1.
