title: Spectroscopic Visualization of Grain Boundaries of Monolayer Molybdenum Disulfide by Stacking Bilayers.
abstract: 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.
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.|Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Seki
authors.initials: S
authors.lastname: Park
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Min Su
authors.initials: MS
authors.lastname: Kim
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.|Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Hyun
authors.initials: H
authors.lastname: Kim
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.|Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Jubok
authors.initials: J
authors.lastname: Lee
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Gang Hee
authors.initials: GH
authors.lastname: Han
authors.affiliation: Department of Physics, University of Seoul , Seoul 130-743, Republic of Korea.
authors.forename: Jeil
authors.initials: J
authors.lastname: Jung
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.|Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Jeongyong
authors.initials: J
authors.lastname: Kim
keywords: grain boundary; indirect band gap photoluminescence; interlayer coupling; monolayer molybdenum disulfide; stacked bilayer