Frank J. Crowne, Matin Amani, A. Glen Birdwell, Matthew L. Chin, Terrance P. O'Regan, Sina Najmaei, Zheng Liu, Pulickel M. Ajayan, Jun Lou, Madan Dubey
The large family of layered transition-metal dichalcogenides is widely believed to constitute a second family of two-dimensional (2D) semiconducting materials that can be used to create novel devices that complement those based on graphene. In many cases these materials have shown a transition from an indirect bandgap in the bulk to a direct bandgap in monolayer systems. In this work we experimentally show that folding a 1H molybdenum disulphide (MoS2) layer results in a turbostratic stack with enhanced photoluminescence quantum yield and a significant shift to the blue by 90 meV. This is in contrast to the expected 2H-MoS2 band structure characteristics, which include an indirect gap and quenched photoluminescence. We present a theoretical explanation to the origin of this behavior in terms of exciton screening.
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http://arxiv.org/abs/1307.1720
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