Apparent Differences between Single Layer Molybdenum Disulfide Fabricated via Chemical Vapor Deposition and Exfoliation

Abstract

Innovative applications based on two-dimensional solids require cost-effective fabrication processes resulting in large areas of high quality materials. Chemical vapour deposition is among the most promising methods to fulfill these requirements. However, for 2D materials prepared in this way it is generally assumed that they are of inferior quality in comparison to the exfoliated 2D materials commonly used in basic research. In this work we challenge this assumption and aim to quantify the differences in quality for the prototypical transition metal dichalcogenide MoS${}_2$. To this end single layers of MoS${}_2$ prepared by different techniques (exfoliation, grown by different chemical vapor deposition methods, transfer techniques, and as vertical heterostructure with graphene) are studied by Raman and photoluminescence spectroscopy, complemented by atomic force microscopy. We demonstrate that as-prepared MoS${}_2$, directly grown on SiO${}_2$, differs from exfoliated MoS${}_2$ in terms of higher photoluminescence, lower electron concentration, and increased strain. As soon as a water film is intercalated (e.g., by transfer) underneath the grown MoS${}_2$, in particular the (opto-)electronic properties become practically identical to those of exfoliated MoS${}_2$. A comparison of the two most common precursors shows that the growth with MoO${}_3$ causes greater strain and/or defect density deviations than growth with ammonium heptamolybdate. As part of a heterostructure directly grown MoS${}_2$ interacts much stronger with the substrate, and in this case an intercalated water film does not lead to the complete decoupling, which is typical for exfoliation or transfer. Our work shows that the supposedly poorer quality of grown 2D transition metal dichalcogenides is indeed a misconception.

References in corpus (27)

• Electric Field Effect in Atomically Thin Carbon Films
• Atomically thin MoS2: A new direct-gap semiconductor
• Two Dimensional Atomic Crystals
• Anomalous Lattice Vibrations of Single and Few-Layer MoS2
• Electrochemically Top Gated Graphene: Monitoring Dopants by Raman Scattering
• Synthesis of Large-Area MoS2 Atomic Layers with Chemical Vapor Deposition
• Observation of tightly bound trions in monolayer MoS2
• Bandgap Engineering of Strained Monolayer and Bilayer MoS2
• How does quantum confinement influence the electronic structure of transition metal sulfides TmS2
• Local strain engineering in atomically thin MoS2
• Strong Photoluminescence Enhancement of MoS2 through Defect Engineering and Oxygen Bonding
• Symmetry-dependent phonon renormalization in monolayer MoS2 transistor
• Optical Separation of Mechanical Strain from Charge Doping in Graphene
• Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2
• Hysteresis in the transfer characteristics of MoS2 transistors
• Photoluminescence of freestanding single- and few-layer MoS2
• Biaxial strain tuning of the optical properties of single-layer transition metal dichalcogenides
• Ultrafast and spatially resolved studies of charge carriers in atomically-thin molybdenum disulfide
• Electrical transport and persistent photoconductivity in monolayer MoS2 phototransistors
• Optical detection of strain and doping inhomogenieties in single layer MoS2
• Excitons versus electron-hole plasma in monolayer transition metal dichalcogenide semiconductors
• Accessing high optical quality of MoS2 monolayers grown by chemical vapor deposition
• Gas dependent hysteresis in MoS${}_2$ field effect transistors
• Charge versus energy transfer in atomically-thin graphene-transition metal dichalcogenide van der Waals heterostructures
• Electron irradiation of metal contacts in monolayer MoS${}_2$ Field-Effect Transistors
• Weakly Trapped, Charged, and Free Excitons in Single-Layer MoS2 in the Presence of Defects, Strain, and Charged Impurities
• Manipulation of the graphene surface potential by ion irradiation

Cited by in corpus (4)

• Electron irradiation of metal contacts in monolayer MoS${}_2$ Field-Effect Transistors
• Dynamic Growth/Etching Model for the Synthesis of Two-Dimensional Transition Metal Dichalcogenides via Chemical Vapour Deposition
• Velocity distributions of particles sputtered from supported 2D-MoS${}_2$ during highly charged ion irradiation
• Isolating the Nonlinear Optical Response of a MoS${}_2$ Monolayer under Extreme Screening of a Metal Substrate