Observation of Switchable Photoresponse of a Monolayer WSe 2 –MoS 2 Lateral Heterostructure via Photocurrent Spectral Atomic Force Microscopic Imaging
Wang, Qing Hua
Strano, Michael S.
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
KAUST Catalysis Center (KCC)
Physics Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
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AbstractIn the pursuit of two-dimensional (2D) materials beyond graphene, enormous advances have been made in exploring the exciting and useful properties of transition metal dichalcogenides (TMDCs), such as a permanent band gap in the visible range and the transition from indirect to direct band gap due to 2D quantum confinement, and their potential for a wide range of device applications. In particular, recent success in the synthesis of seamless monolayer lateral heterostructures of different TMDCs via chemical vapor deposition methods has provided an effective solution to producing an in-plane p-n junction, which is a critical component in electronic and optoelectronic device applications. However, spatial variation of the electronic and optoelectonic properties of the synthesized heterojunction crystals throughout the homogeneous as well as the lateral junction region and the charge carrier transport behavior at their nanoscale junctions with metals remain unaddressed. In this work, we use photocurrent spectral atomic force microscopy to image the current and photocurrent generated between a biased PtIr tip and a monolayer WSe2-MoS2 lateral heterostructure. Current measurements in the dark in both forward and reverse bias reveal an opposite characteristic diode behavior for WSe2 and MoS2, owing to the formation of a Schottky barrier of dissimilar properties. Notably, by changing the polarity and magnitude of the tip voltage applied, pixels that show the photoresponse of the heterostructure are observed to be selectively switched on and off, allowing for the realization of a hyper-resolution array of the switchable photodiode pixels. This experimental approach has significant implications toward the development of novel optoelectronic technologies for regioselective photodetection and imaging at nanoscale resolutions. Comparative 2D Fourier analysis of physical height and current images shows high spatial frequency variations in substrate/MoS2 (or WSe2) contact that exceed the frequencies imposed by the underlying substrates. These results should provide important insights in the design and understanding of electronic and optoelectronic devices based on quantum confined atomically thin 2D lateral heterostructures. © 2016 American Chemical Society.
CitationSon Y, Li M-Y, Cheng C-C, Wei K-H, Liu P, et al. (2016) Observation of Switchable Photoresponse of a Monolayer WSe 2 –MoS 2 Lateral Heterostructure via Photocurrent Spectral Atomic Force Microscopic Imaging . Nano Lett 16: 3571–3577. Available: http://dx.doi.org/10.1021/acs.nanolett.6b00699.
SponsorsM.S. Strano acknowledges a grant from Eni S.p.A. in the frame of the eni-MIT Solar Frontiers Center for support of the SPICIER instrument development. Also, this work was supported by the AFOSR FATE MURI, Grant No. FA9550-15-1-0514. Development of software algorithms for SPICIER were was also supported in part by the U.S. Army Research Laboratory and the U.S. Army Research Office through the Institute for US Soldier Nanotechnologies, under contract number W911NF-13-D-0001. Y. Son is grateful for partial financial support from a Samsung Scholarship. L.J. Li acknowledges the support from King Abdullah University of Science and Technology, Ministry of Science and Technology Taiwan, and Taiwan Consortium of Emergent Crystalline Materials, and AOARD-134137 USA.
PublisherAmerican Chemical Society (ACS)
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