A direct band gap that solely exists in monolayer semiconducting transition metal dichalcogenides (TMDs) endows strong photoluminescence (PL) features, whereas multilayer TMD structures exhibit quenched PL due to the direct-to-indirect band gap transition. We demonstrate multilayer TMD (such as MoS2 and WS2) nanoscrolls with a preserved direct band gap fabricated by an effective and facile method of solvent-driven self-assembly. The resultant multilayer nanoscrolls, exhibiting up to 11 times higher PL intensity than the remanent monolayer, are carefully characterized using PL spectroscopy. Significantly enlarged interlayer distances and modulated interlayer coupling in the fabricated nanostructures are unveiled by cross-sectional scanning transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. The preservation of direct band gap features is further evidenced by density functional theory calculations using the simplified bilayer model with an experimentally obtained 15 Å interlayer distance. The modulation of the PL intensity as an indicator of the band gap crossover in the TMD nanoscrolls is demonstrated by removing the acetone molecules trapped inside the interlayer space. The general applicability of the method presents an opportunity for large-scale fabrication of a plethora of multilayer TMD nanoscrolls with direct band gaps.
KAUST Repository Item: Exported on 2022-09-14
Acknowledged KAUST grant number(s): OSR-2018-CARF/CCF-3079
Acknowledgements: V.T., C.L., and L.C. acknowledge the support from the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR-2018-CARF/CCF-3079. J.-H.F. and C.-C.T. acknowledge the support from the University of Tokyo. L.-J.L. acknowledges the support from the University of Hong Kong; Y.S. acknowledges the support from the National Natural Science Foundation of China (Grant No. 61874074), Shenzhen Peacock Plan (Grant No. KQTD2016 053112042971); S.S. and C.M.C. thank Carl Tryggers Stiftelsen (CTS 20:71) for financial support. The computations were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC) at HPC2N and NSC partially funded by the Swedish Research Council through Grant Agreement No. 2018-05973.