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1. Advances in transferring chemical vapour deposition graphene: a review

   https://doi.org/10.1039/C7MH00485K  

   Chen, Mingguang; Haddon, Robert C.; Yan, Ruoxue; Bekyarova, Elena (January 2017, Materials Horizons)

   The unique two-dimensional structure and outstanding electronic, thermal, and mechanical properties of graphene have attracted the interest of scientists and engineers from various fields. The first step in translating the excellent properties of graphene into practical applications is the preparation of large area, continuous graphene films. Chemical vapour deposition (CVD) graphene has received increasing attention because it provides access to large-area, uniform, and continuous films of high quality. However, current CVD synthetic techniques utilize metal substrates (Cu or Ni) to catalyse the growth of graphene and post-growth transfer of the graphene film to a substrate of interest is critical for most applications such as electronics, photonics, and spintronics. Here we discuss recent advances in the transfer of as-grown CVD graphene to target substrates. The methods that afford CVD graphene on a target substrate are summarized under three categories: transfer with a support layer, transfer without a support layer, and direct growth on target substrates. At present the first two groups dominate the field and research efforts are directed towards refining the choice of the support layer. The support layer plays a vital role in the transfer process because it has direct contact with the atomically thin graphene surface, affecting its properties and determining the quality of the transferred graphene. 

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2. Computational synthesis of 2D materials grown by chemical vapor deposition

   https://doi.org/10.1557/s43578-021-00384-2  

   Momeni, Kasra; Ji, Yanzhou; Chen, Long-Qing (October 2021, Journal of Materials Research)

   AbstractThe exotic properties of 2D materials made them ideal candidates for applications in quantum computing, flexible electronics, and energy technologies. A major barrier to their adaptation for industrial applications is their controllable and reproducible growth at a large scale. A significant effort has been devoted to the chemical vapor deposition (CVD) growth of wafer-scale highly crystalline monolayer materials through exhaustive trial-and-error experimentations. However, major challenges remain as the final morphology and growth quality of the 2D materials may significantly change upon subtle variation in growth conditions. Here, we introduced a multiscale/multiphysics model based on coupling continuum fluid mechanics and phase-field models for CVD growth of 2D materials. It connects the macroscale experimentally controllable parameters, such as inlet velocity and temperature, and mesoscale growth parameters such as surface diffusion and deposition rates, to morphology of the as-grown 2D materials. We considered WSe₂as our model material and established a relationship between the macroscale growth parameters and the growth coverage. Our model can guide the CVD growth of monolayer materials and paves the way to their synthesis-by-design. Graphic abstract 

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3. A computational framework for guiding the MOCVD-growth of wafer-scale 2D materials

   https://doi.org/10.1038/s41524-022-00936-y  

   Momeni, Kasra; Ji, Yanzhou; Nayir, Nadire; Sakib, Nurruzaman; Zhu, Haoyue; Paul, Shiddartha; Choudhury, Tanushree H.; Neshani, Sara; van Duin, Adri C. T.; Redwing, Joan M.; et al (November 2022, npj Computational Materials)

   Abstract Reproducible wafer-scale growth of two-dimensional (2D) materials using the Chemical Vapor Deposition (CVD) process with precise control over their properties is challenging due to a lack of understanding of the growth mechanisms spanning over several length scales and sensitivity of the synthesis to subtle changes in growth conditions. A multiscale computational framework coupling Computational Fluid Dynamics (CFD), Phase-Field (PF), and reactive Molecular Dynamics (MD) was developed – called the CPM model – and experimentally verified. Correlation between theoretical predictions and thorough experimental measurements for a Metal-Organic CVD (MOCVD)-grown WSe₂model material revealed the full power of this computational approach. Large-area uniform 2D materials are synthesized via MOCVD, guided by computational analyses. The developed computational framework provides the foundation for guiding the synthesis of wafer-scale 2D materials with precise control over the coverage, morphology, and properties, a critical capability for fabricating electronic, optoelectronic, and quantum computing devices. 

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4. Towards Low-Temperature CVD Synthesis and Characterization of Mono- or Few-Layer Molybdenum Disulfide

   https://doi.org/10.3390/mi14091758  

   Shendokar, Sachin; Aryeetey, Frederick; Hossen, Moha Feroz; Ignatova, Tetyana; Aravamudhan, Shyam (September 2023, Micromachines)

   Molybdenum disulfide (MoS2) transistors are a promising alternative for the semiconductor industry due to their large on/off current ratio (>1010), immunity to short-channel effects, and unique switching characteristics. MoS2 has drawn considerable interest due to its intriguing electrical, optical, sensing, and catalytic properties. Monolayer MoS2 is a semiconducting material with a direct band gap of ~1.9 eV, which can be tuned. Commercially, the aim of synthesizing a novel material is to grow high-quality samples over a large area and at a low cost. Although chemical vapor deposition (CVD) growth techniques are associated with a low-cost pathway and large-area material growth, a drawback concerns meeting the high crystalline quality required for nanoelectronic and optoelectronic applications. This research presents a lower-temperature CVD for the repeatable synthesis of large-size mono- or few-layer MoS2 using the direct vapor phase sulfurization of MoO3. The samples grown on Si/SiO2 substrates demonstrate a uniform single-crystalline quality in Raman spectroscopy, photoluminescence (PL), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy. These characterization techniques were targeted to confirm the uniform thickness, stoichiometry, and lattice spacing of the MoS2 layers. The MoS2 crystals were deposited over the entire surface of the sample substrate. With a detailed discussion of the CVD setup and an explanation of the process parameters that influence nucleation and growth, this work opens a new platform for the repeatable synthesis of highly crystalline mono- or few-layer MoS2 suitable for optoelectronic application. 

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5. The Line Speed Effect in Roll-to-Roll Dry Transfer of Chemical Vapor Deposition Graphene,

   Hong, N. (December 2021, 2021 International Conference on Micro- and Nano-devices Enabled by R2R Manufacturing)

   Sreenivasan, S.V. (Ed.)

   A roll-to-roll (R2R) technique is especially desirable for transfer of chemical vapor deposition (CVD) graphene towards high-speed, low-cost, renewable, and environmentally friendly manufacturing of graphene-based electronic devices, such as flexible touchscreens, field effect transistors and organic solar cells. A R2R graphene dry transfer system is recently developed. Monolayer graphene is transferred from a copper growth substrate to a polymer backing layer by mechanical peeling. In this work, we present an experimental study to examine the effects of line speed of the mechanical peeling process on the transferred graphene quality. It is shown that the effect of line speed is not monotonic, and an optimal speed exists to yield the highest and most consistent electrical conductivity of transferred graphene among the process conditions studied. This study provides understanding of process parameter effects and demonstrates the potential of the R2R dry transfer process for large-scale CVD graphene toward industrial applications. 

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