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.