Influence of Edges and Interlayer Electron-phonon Coupling in WS 2 /h-BN Heterostructure

• Published in: ACS applied materials & interfaces 2024-07, Vol.16 (30), p.40077-40085
• Main Authors: Paul, Suvodeep, Karak, Saheb, Talukdar, Saswata, Negi, Devesh, Saha, Surajit
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.4c02629

The semiconducting layered transition metal dichalcogenides (e.g., WS ) are excellent candidates for the realization of optoelectronic and nanophotonic applications on account of their band gap tunability, high binding energy and oscillator strength of the excitons, strong light-matter interaction, appreciable charge carrier mobility, and valleytronic properties. However, the photoluminescence (PL) emissions are reported to show a nonuniform spatial distribution, with the edges emitting features like defect-bound excitons and biexcitons at low temperatures in addition to the typical excitons and trions. The appearance of these additional PL features has been shown in the literature to have a strong dependence on the presence of S-vacancies and excess charge carriers. We demonstrate an enhancement of the defect-bound excitons and biexcitons by creating a heterostructure of WS with h-BN where the coupling between the charge carriers in WS with the polar phonons in h-BN governs the enhancement. Furthermore, we have performed a comprehensive resonant Raman study with varying polarization and magnetic field which not only confirms the presence of electron-phonon coupling in WS /h-BN heterostructure, it further demonstrates a thermally induced differential resonance behavior with the excitonic level and the defect-induced midgap states (due to S-vacancies at the edge of WS ) exhibited by a dome-shaped behavior of the Raman intensities with temperature for the normal and defect-induced phonon modes. The defect-bound Raman modes exhibit maximum resonance at ∼240 K while normal Raman modes show at ∼280 K owing to a thermal variation of the electronic states.