Enhanced photoresponse of TiO 2 /MoS 2 heterostructure phototransistors by the coupling of interface charge transfer and
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ijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Magneto-Photoelectrical Composite and Interface Science, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China 2 State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China 3 School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 20 July 2020 / Revised: 22 September 2020 / Accepted: 22 September 2020
ABSTRACT Two-dimensional (2D) MoS2 with appealing physical properties is a promising candidate for next-generation electronic and optoelectronic devices, where the ultrathin MoS2 is usually laid on or gated by a dielectric oxide layer. The oxide/MoS2 interfaces widely existing in these devices have significant impacts on the carrier transport of the MoS2 channel by diverse interface interactions. Artificial design of the oxide/MoS2 interfaces would provide an effective way to break through the performance limit of the 2D devices but has yet been well explored. Here, we report a high-performance MoS2-based phototransistor with an enhanced photoresponse by interfacing few-layer MoS2 with an ultrathin TiO2 layer. The TiO2 is deposited on MoS2 through the oxidation of an e-beam-evaporated ultrathin Ti layer. Upon a visible-light illumination, the fabricated TiO2/MoS2 phototransistor exhibits a responsivity of up to 2,199 A/W at a gate voltage of 60 V and a detectivity of up to 1.67 × 1013 Jones at a zero-gate voltage under a power density of 23.2 μW/mm2. These values are 4.0 and 4.2 times those of the pure MoS2 phototransistor. The significantly enhanced photoresponse of TiO2/MoS2 device can be attributed to both interface charge transfer and photogating effects. Our results not only provide valuable insights into the interactions at TiO2/MoS2 interface, but also may inspire new approach to develop other novel optoelectronic devices based on 2D layered materials.
KEYWORDS MoS2, heterojunction, photodetector, charge injection, photocurrent
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Introduction
Ultrathin two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted intensive interests for their potential applications in next generation electronic and optoelectronic devices [1–7]. As a typical 2D semiconductor in TMDCs, MoS2 is widely explored in field-effect transistors, photodetectors, and solar cells owing to its tunable bandgap and high on‒off ratio [8–12]. In these devices, the hetero-interfaces of metal/MoS2 and oxide/MoS2 at source/drain and gate electrodes have significant impacts on the carrier transport of the ultrathin MoS2 channel. It has been reported that at the interfaces, the height of Schottky barrier can be changed and charges can be injected/withdrawn into/from MoS2 through a variety of mechanisms, including Fermi level pinning [13, 14], charge tra
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