KAUST Grant NumberOSR-2016-CRG5-2996
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AbstractEngineering the substrate of 2D transition metal dichalcogenides can couple the quasiparticle interaction between the 2D material and substrate, providing an additional route to realize conceptual quantum phenomena and novel device functionalities, such as realization of a 12-time increased valley spitting in single-layer WSe2 through the interfacial magnetic exchange field from a ferromagnetic EuS substrate, and band-to-band tunnel field-effect transistors with a subthreshold swing below 60 mV dec−1 at room temperature based on bilayer n-MoS2 and heavily doped p-germanium, etc. Here, it is demonstrated that epitaxially grown single-layer MoS2 on a lattice-matched GaN substrate, possessing a type-I band alignment, exhibits strong substrate-induced interactions. The phonons in GaN quickly dissipate the energy of photogenerated carriers through electron–phonon interaction, resulting in a short exciton lifetime in the MoS2/GaN heterostructure. This interaction enables an enhanced valley helicity at room temperature (0.33 ± 0.05) observed in both steady-state and time-resolved circularly polarized photoluminescence measurements. The findings highlight the importance of substrate engineering for modulating the intrinsic valley carriers in ultrathin 2D materials and potentially open new paths for valleytronics and valley-optoelectronic device applications.
CitationWan Y, Xiao J, Li J, Fang X, Zhang K, et al. (2017) Epitaxial Single-Layer MoS2 on GaN with Enhanced Valley Helicity. Advanced Materials: 1703888. Available: http://dx.doi.org/10.1002/adma.201703888.
SponsorsThis work was supported by the National Key R&D Program of China (Grant No. 2017YFA0206301), the National Basic Research Program of China (Grant No. 2013CB921901), the National Natural Science Foundation of China (Grant Nos. 61521004, 11474007, and 11674005), the King Abdulah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR-2016-CRG5-2996, the National Science Foundation (NSF) under grant 1753380, and the “Youth 1000 Talent Plan” Fund. Y.Y. thanks Ting Cao from University of California, Berkeley, for help discussions.