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Quantum Devices Based on Transition Metal Dichalcogenides


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This final report summarizes a three-year effort to develop and characterize quantum devices based on atomically thin two-dimensional semiconductor transition metal dichalcogenides. Devices consisting of hexagonal boron nitride encapsulated tungsten diselenide contacted by platinum were developed and characterized at low temperatures. Methods for successful process integration of six lithography steps, two 2D material transfers, and two annealing steps were developed. Annealing informing gas was found to be crucial for both heterostructure quality and contact transparency. A technique for transfer of two-dimensional materials without subjecting them to high temperatures was also developed but it was found not to produce superior heterostructure quality compared with conventional techniques. Using a combination of a global accumulation gate and several local confining gates, quantum dots were routinely formed, which displayed quantized charging and, most importantly, quantized energy levels as revealed in transport measurements at mK temperatures. Analysis of typical charging energies and quantum level spacings indicates quantum dot diameters in the range of 20-50 nm, consistent with the lithographic dimensions of the device and the relatively large band gap of tungsten diselenide. We further observed that these devices could be populated with both electrons and holes, which offers opportunities for novel optoelectronic quantum devices.



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