Anomalous photoluminescence thermal quenching of sandwiched single layer MoS_2

Abstract

Abstract:We report an unusual thermal quenching of the micro-photoluminescence (µ-PL) intensity for a sandwiched single-layer (SL) MoS 2 . For this study, MoS 2 layers were chemical vapor deposited on molecular beam epitaxial grown In 0.15 Al 0.85 N lattice matched templates. Later, to accomplish air-stable sandwiched SL-MoS 2 , a thin In 0.15 Al 0.85 N cap layer was deposited on the MoS 2 /In 0.15 Al 0.85 N heterostructure. We confirm that the sandwiched MoS 2 is a single layer from optical and structural analyses using µ-Raman spectroscopy and scanning transmission electron microscopy, respectively. By using high-resolution X-ray photoelectron spectroscopy, no structural phase transition of MoS 2 is noticed. The recombination processes of bound and free excitons were analyzed by the power-dependent µ-PL studies at 77 K and room temperature (RT). The temperature-dependent micro photoluminescence (TDPL) measurements were carried out in the temperature range of 77 -400 K. As temperature increases, a significant red-shift is observed for the free-exciton PL peak, revealing the delocalization of carriers. Further, we observe unconventional negative thermal quenching behavior, the enhancement of the µ-PL intensity with increasing temperatures up to 300K, which is explained by carrier hopping transitions that take place between shallow localized states to the band-edges. Thus, this study renders a fundamental insight into understanding the anomalous thermal quenching of µ-PL intensity of sandwiched SL-MoS 2 . References and links1. H. J. Queisser and E. E. Haller, "Defects in semiconductors: some fatal, some vital," Science 281(5379), 945-950 (1998). 2. S. Nakamura, "The Roles of Structural Imperfections in InGaN-based Blue Light-Emitting Diodes and Laser Diodes," Science 281(5379), 956-961 (1998). 3. B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, "Single-layer MoS 2 transistors," Nat.Nanotechnol. 6(3), 147-150 (2011). Dadap, I. P. Herman, P. Sutter, J. Hone, and R. M. Osgood, Jr., "Direct measurement of the thickness-dependent electronic band structure of MoS 2 using angle-resolved photoemission spectroscopy," Phys.

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