Abstract
Interfacial bubbles are unintentionally created during the transfer of atomically thin 2D layers, a required process in the fabrication of van der Waals heterostructures. By encapsulating a WSe2 monolayer in hBN, we study the differing photoluminescence (PL) properties of the structure resulting from bubble formation. Based on the differentiated absorption probabilities at the bubbles compared to the pristine areas, we demonstrate that the visibility of the bubbles in PL mapping is enhanced when the photoexcitation wavelength lies between the n = 1 and n = 2 resonances of the A-exciton. An appropriate choice of detection window, which includes localized exciton emission but excludes free exciton emission, further improves bubble imaging capability. The interfacial position dependence of the bubbles, whether they are located above or below the WSe2 monolayer, gives rise to measurable consequences in the PL shape.
Highlights
Monolayers of transition metal dichalcogenides (TMDs) such as WSe2, WS2, MoSe2, and MoS2 have attracted considerable attention owing to their intriguing optical and electrical properties and possible applications in optoelectronic devices [1,2,3]
A hBN-encapsulated WSe2 monolayer was obtained by sequentially transferring a bottom hBN flake, ML WSe2, and top hBN flake, which were mechanically exfoliated from bulk crystals, onto a quartz substrate [14]
Our observation indicates that localized exciton (LX) and free exciton (FX) can be selectively generated depending on excitation laser wavelength
Summary
Monolayers of transition metal dichalcogenides (TMDs) such as WSe2, WS2, MoSe2, and MoS2 have attracted considerable attention owing to their intriguing optical and electrical properties and possible applications in optoelectronic devices [1,2,3]. Strong Coulomb interaction in TMD monolayers (MLs) enables the investigation of excitonic complexes such as excitons, trions, and biexcitons [4,5,6,7]. Recent research on TMD MLs has focused on heterostructures comprising different types of 2D materials with the purpose of finding new physical properties and high sample quality [8,9]. Because numerous stacking orders with various materials are possible, new approaches may lead to interesting physical properties
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