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Interlayer Trions in 2D Transition-Metal Dichalcogenide Heterostructures
Biswas Chandan,SEBAIT RIYA 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.10
A dimensionally confined dielectric constant and reduced dielectric screening lead to two-dimensional transition-metal dichalcogenides (TMDs). The confined dielectric constant triggers a strong Coulomb interaction and high exciton binding energies between TMD heterostructures. Here we show a highly efficient interlayer charged exciton or trion formation and its generation sites are present in materials at room temperature. Two different transition metals (Mo, W) and chalcogenide (S, Se) elements were investigated in two different heterostructure combinations (MoS2-WS2 and MoSe2-WS2). Room temperature photoluminescence measurements demonstrate a highly efficient trion formation between and close to the heterostructure interfaces. This study highlights an effective band alignment, strong photoexciting Coulomb interaction, and formation of interlayer trions with different recombination energies. This investigation suggests the possibility of utilizing interlayer trions in promising optoelectronic devices in the future.
Daw Debottam,Sebait Riya,Biswas Chandan 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.10
Rotationally aligned, two-dimensional (2D), transition-metal dichalcogenides (TMDs) exhibit unique electronic, optical, and optoelectronic properties compared to random stacking. Rotationally aligned graphene stacking was demonstrated previously for numerous exotic phenomena, such as superconductivity, resonant tunneling, and moiré pattern. However, rotationally aligned dry-transfer techniques of TMDs, have yet to be demonstrated. Here, we show a simple method of selective cutting of a few-layer tungsten diselenide (WSe2) flake and rotationally aligning it by using dry-transfer stacking. The dry transfer techniques used for this study were adapted to maintain low sample contamination, a high-quality interface, a low number of defects. A combination of viscoelastic and thermoelastic materials was used for the TMD pickup and release to facilitate the rotationally aligned stacking. Aligned WSe2 stacks were characterized by Raman and photoluminescence spectroscopy to evaluate the integrity of the fabricated stack. This study highlights the possibility of using a rotationally aligned, artificial stacking method for exfoliated TMD materials for future electronic and optoelectronic applications.