Carrier-Type Modulation and Mobility Improvement of Thin MoTe.

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Advanced materials (Deerfield Beach, Fla.), ISSN: 1521-4095, Vol: 29, Issue: 39

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Qu, Deshun; Liu, Xiaochi; Huang, Ming; Lee, Changmin; Ahmed, Faisal; Kim, Hyoungsub; Ruoff, Rodney S.; Hone, James; Yoo, Won Jong
Materials Science; Engineering
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A systematic modulation of the carrier type in molybdenum ditelluride (MoTe ) field-effect transistors (FETs) is described, through rapid thermal annealing (RTA) under a controlled O environment (p-type modulation) and benzyl viologen (BV) doping (n-type modulation). Al O capping is then introduced to improve the carrier mobilities and device stability. MoTe is found to be ultrasensitive to O at elevated temperatures (250 °C). Charge carriers of MoTe flakes annealed via RTA at various vacuum levels are tuned between predominantly pristine n-type ambipolar, symmetric ambipolar, unipolar p-type, and degenerate-like p-type. Changes in the MoTe -transistor performance are confirmed to originate from the physical and chemical absorption and dissociation of O , especially at tellurium vacancy sites. The electron branch is modulated by varying the BV dopant concentrations and annealing conditions. Unipolar n-type MoTe FETs with a high on-off ratio exceeding 10 are achieved under optimized doping conditions. By introducing Al O capping, carrier field effect mobilities (41 for holes and 80 cm V s for electrons) and device stability are improved due to the reduced trap densities and isolation from ambient air. Lateral MoTe p-n diodes with an ideality factor of 1.2 are fabricated using the p- and n-type doping technique to test the superb potential of the doping method in functional electronic device applications.