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HL: Fachverband Halbleiterphysik
HL 59: 2D Semiconductors and van der Waals Heterostructures VI
HL 59.5: Vortrag
Freitag, 21. März 2025, 10:30–10:45, H15
Effect of the Direct-to-Indirect Bandgap Crossover on the Reverse Energy Transfer — •Gayatri Gayatri1, Debashish Das2, Natalia Zawadzka1, Takashi Taniguchi3, Kenji Watanabe3, Adam Babiński1, Saroj K. Nayak2, Maciej R. Molas1, and Arka Karmakr1 — 1University of Warsaw, Warsaw, Poland — 2Indian Institute of Technology Bhubaneswar, Odisha, India — 3National Institute for Materials Science, Ibaraki, Japan
Heterostructures (HSs) made by the vertical stacking of van der Waals monolayers (1Ls) have shown great potential in (opto)electronic devices. In the type-II transition metal dichalcogenide HSs, long-range energy transfer (ET) happens via the dipole-dipole coupling (Förster type). To investigate this, we studied HS made by the 1L tungsten disulfide (WS2) and 1L-5Ls molybdenum disulfide (MoS2), with hexagonal boron nitride (hBN) as a charge-blocking interlayer, using differential reflection contrast, photoluminescence (PL), and photoluminescence excitation. At room temperature, PL enhancement has been observed in the neutral exciton of WS2 in the WS2-hBN-1L MoS2 and WS2-hBN-2L MoS2 regions as compared to the isolated WS2 emission. This enhancement confirms an efficient ET from MoS2 B excitonic level to WS2 A excitonic level. As the number of MoS2 layers increases, bandgap changes from direct-to-indirect, promoting more immediate carrier scattering from the K-valley. Consequently, carrier population decreases and ET becomes less effective.
Keywords: 2D Heterostructure; Transition Metal Dichalcogenides (TMDs); Förster Resonance Energy Transfer (FRET); Heterostructure light matter interaction; Bandgap Transition