A direct comparison of CVD-grown and exfoliated MoS2 using optical spectroscopy

Abstract

MoS2 is a highly interesting material system, which exhibits a crossover from an indirect band gap in the bulk crystal to a direct gap for single layers. Here, we perform a direct comparison between large-area MoS${}_2$ films grown by chemical vapor deposition (CVD) and MoS${}_2$ flakes prepared by mechanical exfoliation from natural bulk crystal. Raman spectroscopy measurements show differences between the in-plane and out-of-plane phonon mode positions in CVD-grown and exfoliated MoS${}_2$. Photoluminescence (PL) mapping reveals large regions in the CVD-grown films that emit strong PL at room temperature, and low-temperature PL scans demonstrate a large spectral shift of the A exciton emission as a function of position. Polarization-resolved PL measurements under near-resonant excitation conditions show a strong circular polarization of the PL, corresponding to a valley polarization.

References in corpus (12)

• Two Dimensional Atomic Crystals
• Anomalous Lattice Vibrations of Single and Few-Layer MoS2
• Valley polarization in MoS2 monolayers by optical pumping
• Integrated Circuits Based on Bilayer MoS2 Transistors
• Symmetry-dependent phonon renormalization in monolayer MoS2 transistor
• Nonvolatile Memory Cells Based on MoS2/Graphene Heterostructures
• Robust optical emission polarization in MoS2 monolayers through selective valley excitation
• Visibility of dichalcogenide nanolayers
• Vapor-Solid Growth of High Optical Quality MoS2 Monolayers With Near-Unity Valley Polarization
• Optical identification of atomically thin dichalcogenide crystals
• Raman spectroscopy of the interlayer shear mode in few-layer MoS2 flakes
• Electronic structure of two-dimensional crystals from ab-initio theory

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• Accessing high optical quality of MoS2 monolayers grown by chemical vapor deposition
• Ultrafast mid-infrared nanoscopy of strained vanadium dioxide nanobeams
• Large-Scale Arrays of Single- and Few-Layer MoS2 Nanomechanical Resonators
• Characterization of highly crystalline lead iodide nanosheets prepared by room-temperature solution processing
• Effects of CVD Growth Parameters on Global and Local Optical Properties of MoS${}_2$ Monolayers
• Optical spectroscopy of interlayer coupling in artificially stacked MoS2 layers
• High Throughput Characterization of Epitaxially Grown Single-Layer MoS2
• Anisotropic Electron-Photon-Phonon Coupling in Layered MoS2
• Spatiotemporal dynamics of free and bound excitons in CVD-grown MoS${}_2$ monolayer
• Towards a 2D Printer: A Deterministic Cross Contamination-free Transfer Method for Atomically Layered Materials