Visualizing nanoscale excitonic relaxation properties of disordered edges and grain boundaries in monolayer molybdenum disulfide

Authors

Wei Bao, Lawrence Berkeley National Laboratory & University of California Berkeley
Nicholas J. Borys, Lawrence Berkeley National Laboratory
Changhyun Ko, University of California Berkeley
Joonki Suh, University of California Berkeley
Wen Fan, University of California Berkeley
Andrew Thron, Lawrence Berkeley National Laboratory
Yingjie Zhang, Lawrence Berkeley National Laboratory & University of California Berkeley
Alexander Buyanin, Lawrence Berkeley National Laboratory & University of California Berkeley
Jie Zhang, Lawrence Berkeley National Laboratory
Stefano Cabrini, Lawrence Berkeley National Laboratory
Paul D. Ashby, Lawrence Berkeley National Laboratory
Alexander Weber-Bargioni, Lawrence Berkeley National Laboratory
Sefaattin Tongay, University of California Berkeley & Arizona State University
Shaul Aloni, awrence Berkeley National Laboratory
D. Frank Ogletree, Lawrence Berkeley National Laboratory
Junqiao Wu, Lawrence Berkeley National Laboratory & University of California Berkeley
Miquel B. Salmeron, Lawrence Berkeley National Laboratory & University of California Berkeley
P. James Schuck, Lawrence Berkeley National Laboratory

Document Type

Article

Date of this Version

2015

Citation

NATURE COMMUNICATIONS | 6:7993 | DOI: 10.1038/ncomms8993 | www.nature.com/naturecommunications

Comments

2015 Macmillan Publishers Limited. All rights reserved.

Abstract

Two-dimensional monolayer transition metal dichalcogenide semiconductors are ideal building blocks for atomically thin, flexible optoelectronic and catalytic devices. Although challenging for two-dimensional systems, sub-diffraction optical microscopy provides a nanoscale material understanding that is vital for optimizing their optoelectronic properties. Here we use the ‘Campanile’ nano-optical probe to spectroscopically image exciton recombination within monolayer MoS2 with sub-wavelength resolution (60 nm), at the length scale relevant to many critical optoelectronic processes. Synthetic monolayer MoS2 is found to be composed of two distinct optoelectronic regions: an interior, locally ordered but mesoscopically heterogeneous two-dimensional quantum well and an unexpected B300-nm wide, energetically disordered edge region. Further, grain boundaries are imaged with sufficient resolution to quantify local exciton-quenching phenomena, and complimentary nano-Auger microscopy reveals that the optically defective grain boundary and edge regions are sulfur deficient. The nanoscale structure–property relationships established here are critical for the interpretation of edge- and boundary-related phenomena and the development of next-generation two-dimensional optoelectronic devices.