Spectroscopic Visualization of Grain Boundaries of Monolayer Molybdenum Disulfide by Stacking Bilayers

• Published in: ACS nano Vol. 9; no. 11; pp. 11042 - 11048
• Main Authors: Park, Seki, Kim, Min Su, Kim, Hyun, Lee, Jubok, Han, Gang Hee, Jung, Jeil, Kim, Jeongyong
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24.11.2015
• Subjects: stacked bilayer; indirect band gap photoluminescence; interlayer coupling; monolayer molybdenum disulfide; grain boundary
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.5b04977

Polycrystalline growth of molybdenum disulfide (MoS2) using chemical vapor deposition (CVD) methods is subject to the formation of grain boundaries (GBs), which have a large effect on the electrical and optical properties of MoS2-based optoelectronic devices. The identification of grains and GBs of CVD-grown monolayer MoS2 has traditionally required atomic resolution microscopy or nonlinear optical imaging techniques. Here, we present a simple spectroscopic method for visualizing GBs of polycrystalline monolayer MoS2 using stacked bilayers and mapping their indirect photoluminescence (PL) peak positions and Raman peak intensities. We were able to distinguish a GB between two MoS2 grains with tilt angles as small as 6° in their grain orientations and, based on the inspection of several GBs, found a simple empirical rule to predict the location of the GBs. In addition, the large number of twist angle domains traced through our facile spectroscopic mapping technique allowed us to identify a continuous evolution of the coupled structural and optical properties of bilayer MoS2 in the vicinity of the 0° and 60° commensuration angles which were explained by elastic deformation model of the MoS2 membranes.