Vapor-Solid Growth of High Optical Quality MoS2 Monolayers With Near-Unity Valley Polarization

Abstract

Monolayers of transition metal dichalcogenides (TMDCs) are atomically thin direct-gap semiconductors with potential applications in nanoelectronics, optoelectronics, and electrochemical sensing. Recent theoretical and experimental efforts suggest that they are ideal systems for exploiting the valley degrees of freedom of Bloch electrons. For example, Dirac valley polarization has been demonstrated in mechanically exfoliated monolayer MoS2 samples by polarization-resolved photoluminescence, although polarization has rarely been seen at room temperature. Here we report a new method for synthesizing high optical quality monolayer MoS2 single crystals up to 25 microns in size on a variety of standard insulating substrates (SiO2, sapphire and glass) using a catalyst-free vapor-solid growth mechanism. The technique is simple and reliable, and the optical quality of the crystals is extremely high, as demonstrated by the fact that the valley polarization approaches unity at 30 K and persists at 35% even at room temperature, suggesting a virtual absence of defects. This will allow greatly improved optoelectronic TMDC monolayer devices to be fabricated and studied routinely.

14 pages (manuscript) + 4 pages (supplementary materials), including 6 figures in manuscript. To appear in ACS Nano

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• Carrier and polarization dynamics in monolayer MoS2
• Influence of Stoichiometry on the Optical and Electrical Properties of Chemical Vapor Deposition Derived MoS${}_2$
• Valley Carrier Dynamics in Monolayer Molybdenum Disulphide from Helicity Resolved Ultrafast Pump-probe Spectroscopy
• Mechanics of freely-suspended ultrathin layered materials
• A direct comparison of CVD-grown and exfoliated MoS2 using optical spectroscopy
• Large Current Modulation and Spin-Dependent Tunneling of Vertical Graphene/MoS${}_2$ Heterostructures
• Tuning valley polarization in a WSe2 monolayer with a tiny magnetic field
• NaCl-Assisted Substrate Dependent 2D Planar Nucleated Growth of MoS2
• Intervalley coupling by quantum dot confinement potentials in monolayer transition metal dichalcogenides
• Layer-Transferred MoS2/GaN PN Diodes
• Understanding Variations in Circularly Polarized Photoluminescence in Monolayer Transition Metal Dichalcogenides
• Majorana Fermions on Zigzag Edge of Monolayer Transition Metal Dichalcogenides
• Epitaxial Growth of Large Area Single-Crystalline Few-Layer MoS2 with Room Temperature Mobility of 192 cm2V-1s-1
• Single layer MoS2 nanoribbon field effect transistor
• Illuminating Invisible Grain Boundaries in Coalesced Single-Orientation WS2 Monolayer Films
• The role of surface chemical reactivity in the stability of electronic nanodevices based on two-dimensional materials "beyond graphene" and topological insulators
• Adhesion of 2D MoS${}_2$ to Graphite and Metal Substrates Measured by a Blister Test
• Transport properties of the top and bottom surfaces in monolayer MoS2 grown by chemical vapor deposition
• Surface-Confined Two-Dimensional Crystal Growth on a Monolayer
• Electrical control of intervalley scattering in graphene via the charge state of defects
• Optical spectroscopy of interlayer coupling in artificially stacked MoS2 layers
• High Throughput Characterization of Epitaxially Grown Single-Layer MoS2
• Strain induced effects on the electronic and phononic properties of 2H and 1T${}^{\prime }$ monolayer MoS${}_2$
• Microscopic mechanism of van der Waals heteroepitaxy in the formation of MoS2/hBN vertical heterostructures
• Synthesis and optical properties of large-scale single-crystalline two-dimensional semiconductor WS2 monolayer from chemical vapor deposition
• Magnetoresistance in Noncentrosymmetric Two-dimensional Systems
• Coherent electron dynamics in monolayer ${\text{MoS}}_2$ under ultrashort optical pulse
• Momentum selective optical absorption in triptycene molecular membrane
• Lateral heterojunctions within monolayer semiconductors