Observation of Switchable Photoresponse of a Monolayer WSe2-MoS2 Lateral Heterostructure via Photocurrent Spectral Atomic Force Microscopic Imaging.
In 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.
Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
Youngwoo
Y
Son
Physics Science and Engineering Division, King Abdullah University of Science and Technology , Thuwal 23955-6900, Kingdom of Saudi Arabia.|Research Center for Applied Sciences, Academia Sinica , Taipei 10617, Taiwan.
Ming-Yang
MY
Li
Department of Material Science and Engineering, National Chiao Tung University , Hsinchu 300, Taiwan.
Chia-Chin
CC
Cheng
Department of Material Science and Engineering, National Chiao Tung University , Hsinchu 300, Taiwan.
Kung-Hwa
KH
Wei
Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
Pingwei
P
Liu
Materials Science and Engineering, School for Engineering of Matter, Transport and Energy, Arizona State University , Tempe, Arizona 85287, United States.
Qing Hua
QH
Wang
Physics Science and Engineering Division, King Abdullah University of Science and Technology , Thuwal 23955-6900, Kingdom of Saudi Arabia.
Lain-Jong
LJ
Li
Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
Michael S
MS
Strano
MoS2; Two-dimensional materials; WSe2; heterostructure; photoresponsivity; transition metal dichalcogenides