Approaching the Intrinsic Limit in Transition Metal Dichalcogenide van der Waals Heterostructures

9th September 2020

Timing : 1 pm EST

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For a list of all talks at the NanoBio seminar Series 2020, see here

Studying the intrinsic behavior 2D materials requires attention to both external and internal sources of disorder. This talk will first review the techniques used to create clean heterostructures with hBN to reduce environmental disorder. In graphene, ten years of progress has led to device performance now rivaling he highest-quality GaAs-based heterostructures. On the other hand, semiconducting transition metal dichalcogenides (TMDs) are also limited by atomic defects within the crystalline layers, which requires efforts in synthesis and characterization of high purity crystals. This talk will present recent progress in synthesis of TMD crystals with dramatically lower defect density using a self-flux technique. Combining higher crystal quality and clean encapsulation allows observation of greatly enhanced optical properties, including near-unity photoluminescence quantum yield, and long excited-state lifetime in TMD heterostructures. In addition, electronic transport measurements show improved carrier mobility and reveal many new details in magnetotransport measurements, including observation of fractional quantum Hall states in monolayer TMDs. These high-quality crystals also allow studies of twisted bilayer TMDs, which show the emergence of many-body correlated states.