Showing papers on "Chemical vapor deposition published in 2017"

Wafer-Scale Growth and Transfer of Highly-Oriented Monolayer MoS2 Continuous Films

Abstract: Large scale epitaxial growth and transfer of monolayer MoS2 has attracted great attention in recent years. Here, we report the wafer-scale epitaxial growth of highly oriented continuous and uniform monolayer MoS2 films on single-crystalline sapphire wafers by chemical vapor deposition (CVD) method. The epitaxial film is of high quality and stitched by many 0°, 60° domains and 60°-domain boundaries. Moreover, such wafer-scale monolayer MoS2 films can be transferred and stacked by a simple stamp-transfer process, and the substrate is reusable for subsequent growth. Our progress would facilitate the scalable fabrication of various electronic, valleytronic, and optoelectronic devices for practical applications.

Handbook of Thin Film Process Technology: 98/1 Reactive Sputtering

Abstract: PHYSICAL DEPOSITION TECHNIQUES Thermal Evaporation (Coordinating Editors: E.B. Graper and J. Vossen) Introduction and general discussion (E.B. Graper) Resistance evaporation (E.B. Graper) Electron beam evaporation (E.B. Graper) Ion vapor evaporation (E.B. Graper) Cathodic arc deposition (P.J. Martin) Laser ablation (A. Morimoto and T. Shimizu) Molecular Beam Epitaxy (Coordinating Editors: S.A. Barnett and J. Poate) Introduction and general discussion (S.A. Barnett and I.T. Ferguson) Semiconductor growth by metalorganic molecular beam epitaxy (MOMBE) (C.R. Abernathy) Gas-source MBE (G.Y. Robinson) Chemical beam epitaxy (T.H. Chiu) Thin film deposition and dopant incorporation by energetic particle sources (S. Strite and H. Morkoc) Sputtering (Coordinating Editors: S.I. Shah and D. Glocker) Introduction and general discussion (S.I. Shah) Glow discharge sputtering (A.S. Penfold) Magneton sputtering (A.S. Penfold) Ion-beam sputtering (T. Itoh) Thermal Spraying (Coordinating Editor: R.C. Tucker Jr.) Introduction to thermal spray coatings (R.C. Tucker Jr.) Flame spray (P.A. Kammer) Plasma spray coatings (R.C. Tucker Jr.) High velocity oxy-fuel coatings (R.C. Tucker Jr.) Detonation gun deposition (R.C. Tucker Jr.) Mechanical, wear, corrosion, and other properties of thermal spray coatings (R.C. Tucker Jr.) CHEMICAL DEPOSITION TECHNIQUES Chemical Vapor Deposition (Coordinating Editor: L. Vescan) Introduction and general discussion (L. Vescan) Metalorganic chemical vapour deposition (MOCVD) (R.D. Dupuis) Photoassisted chemical vapour deposition (S.J.C. Irvine) Thermally activated chemical vapour deposition (L. Vescan) Atomic layer epitaxy (T. Suntola) PROCESSING TECHNOLOGIES Pattern Transfer (Coordinating Editor: J.W. Coburn Introduction and general discussion (J.W. Coburn) Reactive ion etching (C. Steinbruchel) Ion-beam-based chemical dry etching (C. Steinbruchel) Ion milling (C. Steinbruchel) REAL-TIME DIAGNOSTICS Introduction and General Discussion (Coordinating Editor: R.W. Collins) Diagnostic Techniques Reflection high-energy electron diffraction as a diagnostic technique (B.A. Joyce) Low-energy electron diffraction (Sheng-Liang Chang and P.A. Thiel) Reflection mass spectroscopy (R. Kaspi) Optical Diagnostics Infrared emission interferometry (A.J. Springthorpe) Reflectance anisotropy (B. Drevillon) Interferometry as an in situ probe during processing of semiconductor wafers (V.M. Donnelly) Ellipsometry (P. Snyder) Photoluminescence (P.R. Berger) Elastic laser light scattering (B. Gallois) Plasma Probes Langmuir probe diagnostics (N. Hershkowitz) Microwave interferometers (R.A. Breun) Atomic absorption spectroscopy (Chih-shun Lu) Other Diagnostics (Coordinating Editor: R. Collins) Quartz monitors and microbalances (J. Krim and C. Daly) Probes of film stress (D. Glocker) SURFACE MODIFICATION IN VACUUM Processes for Substrate Cleaning (D. Mattox) Surface Treatment for Corrosion and Wear Protection Material aspects of corrosion protection (Cathy Cotell) Ion implantation with beams (Mike Nastasi) Plasma source ion implantation (Donald Rej) Surface Treatment of Polymers for Adhesion Plasma sources for polymer surface treatment (M.R. Wertheimer and Edward Liston) Surface chemistry of treated polymers (Lou Gerenser) MATERIALS Hard and Protective Materials Introduction (O. Knotek and A. Schrey) TiN TiAIN TiAIVN CrN ZrN HfN BN Diamond Ni-Cr-B-Si Al-bronze Al2O3-TiO2 Electronic Materials Introduction (K. Cadien and S. Sivaram) GaAs a-Si:H AlGaAs Tellurides CuInSe2 Si Ge Si-Ge W GaN AIN ErAs Quaternaries Silicides SiSnC SiN Optical Materials Introduction (J. Targove) AIN ZnO PbTiO3 KNbO3 Ferroelectric Materials Introduction (M. Sayer) Bi4Ti3O12 LiNbO3 and LiTaO3 PbTiO3/PbZrTiO3 Ferromagnetic Materials Introduction (E.M.T. Velu and D.N. Lambeth) CoCr TbFeCo CoPt/CoPd GdTbFe Superconducting Materials Introduction (J. Azoulay) NbN YBa2Cu3O7 Thallium-based compounds Mercury-based compounds Miscellaneous Materials PTFE PPN Ir/Pt Appendix A: List of Contributors Subject Index

Direct Synthesis of Large-Area 2D Mo 2 C on In Situ Grown Graphene.

Abstract: As a new member of the MXene group, 2D Mo2 C has attracted considerable interest due to its potential application as electrodes for energy storage and catalysis. The large-area synthesis of Mo2 C film is needed for such applications. Here, the one-step direct synthesis of 2D Mo2 C-on-graphene film by molten copper-catalyzed chemical vapor deposition (CVD) is reported. High-quality and uniform Mo2 C film in the centimeter range can be grown on graphene using a Mo-Cu alloy catalyst. Within the vertical heterostructure, graphene acts as a diffusion barrier to the phase-segregated Mo and allows nanometer-thin Mo2 C to be grown. Graphene-templated growth of Mo2 C produces well-faceted, large-sized single crystals with low defect density, as confirmed by scanning transmission electron microscopy (STEM) measurements. Due to its more efficient graphene-mediated charge-transfer kinetics, the as-grown Mo2 C-on-graphene heterostructure shows a much lower onset voltage for hydrogen evolution reactions as compared to Mo2 C-only electrodes.

High-Performance Polymers Sandwiched with Chemical Vapor Deposited Hexagonal Boron Nitrides as Scalable High-Temperature Dielectric Materials

Abstract: Polymer dielectrics are the preferred materials of choice for power electronics and pulsed power applications. However, their relatively low operating temperatures significantly limit their uses in harsh-environment energy storage devices, e.g., automobile and aerospace power systems. Herein, hexagonal boron nitride (h-BN) films are prepared from chemical vapor deposition (CVD) and readily transferred onto polyetherimide (PEI) films. Greatly improved performance in terms of discharged energy density and charge-discharge efficiency is achieved in the PEI sandwiched with CVD-grown h-BN films at elevated temperatures when compared to neat PEI films and other high-temperature polymer and nanocomposite dielectrics. Notably, the h-BN-coated PEI films are capable of operating with >90% charge-discharge efficiencies and delivering high energy densities, i.e., 1.2 J cm-3 , even at a temperature close to the glass transition temperature of polymer (i.e., 217 °C) where pristine PEI almost fails. Outstanding cyclability and dielectric stability over a straight 55 000 charge-discharge cycles are demonstrated in the h-BN-coated PEI at high temperatures. The work demonstrates a general and scalable pathway to enable the high-temperature capacitive energy applications of a wide range of engineering polymers and also offers an efficient method for the synthesis and transfer of 2D nanomaterials at the scale demanded for applications.

Chemical Vapor Deposition of Large-Size Monolayer MoSe2 Crystals on Molten Glass.

Abstract: We report the fast growth of high-quality millimeter-size monolayer MoSe2 crystals on molten glass using an ambient pressure CVD system. We found that the isotropic surface of molten glass suppresses nucleation events and greatly improves the growth of large crystalline domains. Triangular monolayer MoSe2 crystals with sizes reaching ∼2.5 mm, and with a room-temperature carrier mobility up to ∼95 cm2/(V·s), can be synthesized in 5 min. The method can also be used to synthesize millimeter-size monolayer MoS2 crystals. Our results demonstrate that “liquid-state” glass is a highly promising substrate for the low-cost growth of high-quality large-size 2D transition metal dichalcogenides (TMDs).

Stitching h-BN by atomic layer deposition of LiF as a stable interface for lithium metal anode.

Abstract: Defects are important features in two-dimensional (2D) materials that have a strong influence on their chemical and physical properties. Through the enhanced chemical reactivity at defect sites (point defects, line defects, etc.), one can selectively functionalize 2D materials via chemical reactions and thereby tune their physical properties. We demonstrate the selective atomic layer deposition of LiF on defect sites of h-BN prepared by chemical vapor deposition. The LiF deposits primarily on the line and point defects of h-BN, thereby creating seams that hold the h-BN crystallites together. The chemically and mechanically stable hybrid LiF/h-BN film successfully suppresses lithium dendrite formation during both the initial electrochemical deposition onto a copper foil and the subsequent cycling. The protected lithium electrodes exhibit good cycling behavior with more than 300 cycles at relatively high coulombic efficiency (>95%) in an additive-free carbonate electrolyte.

Controlled Synthesis of High-Mobility Atomically Thin Bismuth Oxyselenide Crystals.

Abstract: Non-neutral layered crystals, another group of two-dimensional (2D) materials that lack a well-defined van der Waals (vdWs) gap, are those that form strong chemical bonds in-plane but display weak out-of-plane electrostatic interactions, exhibiting intriguing properties for the bulk counterpart. However, investigation of the properties of their atomically thin counterpart are very rare presumably due to the absence of efficient ways to achieve large-area high-quality 2D crystals. Here, high-mobility atomically thin Bi2O2Se, a typical non-neutral layered crystal without a standard vdWs gap, was synthesized via a facial chemical vapor deposition (CVD) method, showing excellent controllability for thickness, domain size, nucleation site, and crystal-phase evolution. Atomically thin, large single crystals of Bi2O2Se with lateral size up to ∼200 μm and thickness down to a bilayer were obtained. Moreover, optical and electrical properties of the CVD-grown 2D Bi2O2Se crystals were investigated, displaying a size...

Van der Waals Epitaxial Growth of 2D Metallic Vanadium Diselenide Single Crystals and their Extra-High Electrical Conductivity.

Abstract: 2D metallic transition-metal dichalcogenides (MTMDs) have recently emerged as a new class of materials for the engineering of novel electronic phases, 2D superconductors, magnets, as well as novel electronic applications. However, the mechanical exfoliation route is predominantly used to obtain such metallic 2D flakes, but the batch production remains challenging. Herein, the van der Waals epitaxial growth of monocrystalline, 1T-phase, few-layer metallic VSe2 nanosheets on an atomically flat mica substrate via a "one-step" chemical vapor deposition method is reported. The thickness of the VSe2 nanosheets is precisely tuned from several nanometers to several tenths of nanometers. More significantly, the 2D VSe2 single crystals are found to present an excellent metallic feature, as evidenced by the extra-high electrical conductivity of up to 106 S m-1 , 1-4 orders of magnitude higher than that of various conductive 2D materials. The thickness-dependent charge-density-wave phase transitions are also examined through low-temperature transport measurements, which reveal that the synthesized 2D metallic 1T-VSe2 nanosheets should serve as good research platforms for the detecting novel many-body states. These results open a new path for the synthesis and property investigations of nanoscale-thickness 2D MTMDs crystals.

High-Mobility Multilayered MoS2 Flakes with Low Contact Resistance Grown by Chemical Vapor Deposition

Abstract: The controlled synthesis of high-quality multilayer (ML) MoS2 flakes with gradually shrinking basal planes by chemical vapor deposition (CVD) is demonstrated. These CVD-grown ML MoS2 flakes exhibit much higher mobility and current density than mechanically exfoliated ML flakes due to the reduced contact resistance which mainly resulted from direct contact between the lower MoS2 layers and electrodes.

Large-Area and High-Quality 2D Transition Metal Telluride.

Abstract: Large-area and high-quality 2D transition metal tellurides are synthesized by the chemical vapor deposition method. The as-grown WTe2 maintains two different stacking sequences in the bilayer, where the atomic structure of the stacking boundary is revealed by scanning transmission electron microscopy. The low-temperature transport measurements reveal a novel semimetal-to-insulator transition in WTe2 layers and an enhanced superconductivity in few-layer MoTe2 .

Controlled Synthesis of Ultrathin 2D β-In2S3 with Broadband Photoresponse by Chemical Vapor Deposition

Abstract: β-In2S3 is a natural defective III–VI semiconductor attracting considerable interests but lack of efficient method for its 2D form fabrication. Here, for the first time, this paper reports controlled synthesis of ultrathin 2D β-In2S3 flakes via a facile space-confined chemical vapor deposition method. The natural defects in β-In2S3 crystals, clearly revealed by optical spectra and optoelectronic measurement, strongly modulate the (opto)-electronic of as-fabricated β-In2S3 and render it a broad detection range from visible to near-infrared. Particularly, the as-fabricated β-In2S3 photodetector shows a high photoresponsivity of 137 A W−1, a high external quantum efficiency of 3.78 × 104%, and a detectivity of 4.74 × 1010 Jones, accompanied with a fast rise and decay time of 6 and 8 ms, respectively. In addition, an interesting linear response to the testing power intensities range is observed, which can also be understood by the presence of natural defects. The unique defective structure and intrinsic optical properties of β-In2S3, together with its controllable growth, endow it with great potential for future applications in electronics and optoelectronics.

Re Doping in 2D Transition Metal Dichalcogenides as a New Route to Tailor Structural Phases and Induced Magnetism

Abstract: Alloying in 2D results in the development of new, diverse, and versatile systems with prospects in bandgap engineering, catalysis, and energy storage. Tailoring structural phase transitions using alloying is a novel idea with implications in designing all 2D device architecture as the structural phases in 2D materials such as transition metal dichalcogenides are correlated with electronic phases. Here, this study develops a new growth strategy employing chemical vapor deposition to grow monolayer 2D alloys of Re-doped MoSe2 with show composition tunable structural phase variations. The compositions where the phase transition is observed agree well with the theoretical predictions for these 2D systems. It is also shown that in addition to the predicted new electronic phases, these systems also provide opportunities to study novel phenomena such as magnetism which broadens the range of their applications.

Tailoring the thermal and electrical transport properties of graphene films by grain size engineering

Abstract: Understanding the influence of grain boundaries (GBs) on the electrical and thermal transport properties of graphene films is essentially important for electronic, optoelectronic and thermoelectric applications. Here we report a segregation-adsorption chemical vapour deposition method to grow well-stitched high-quality monolayer graphene films with a tunable uniform grain size from ∼200 nm to ∼1 μm, by using a Pt substrate with medium carbon solubility, which enables the determination of the scaling laws of thermal and electrical conductivities as a function of grain size. We found that the thermal conductivity of graphene films dramatically decreases with decreasing grain size by a small thermal boundary conductance of ∼3.8 × 109 W m-2 K-1, while the electrical conductivity slowly decreases with an extraordinarily small GB transport gap of ∼0.01 eV and resistivity of ∼0.3 kΩ μm. Moreover, the changes in both the thermal and electrical conductivities with grain size change are greater than those of typical semiconducting thermoelectric materials.

Chemical Vapor Deposition Growth of Few-Layer MoTe2 in the 2H, 1T′, and 1T Phases: Tunable Properties of MoTe2 Films

Abstract: Chemical vapor deposition allows the preparation of few-layer films of MoTe2 in three distinct structural phases depending on the growth quench temperature: 2H, 1T′, and 1T. We present experimental and computed Raman spectra for each of the phases and utilize transport measurements to explore the properties of the 1T MoTe2 phase. Density functional theory modeling predicts a (semi-)metallic character. Our experimental 1T films affirm the former, show facile μA-scale source-drain currents, and increase in conductivity with temperature, different from the 1T′ phase. Variation of the growth method allows the formation of hybrid films of mixed phases that exhibit susceptibility to gating and significantly increased conductivity.

Suppressing Nucleation in Metal-Organic Chemical Vapor Deposition of MoS2 Monolayers by Alkali Metal Halides.

Abstract: Toward the large-area deposition of MoS2 layers, we employ metal–organic precursors of Mo and S for a facile and reproducible van der Waals epitaxy on c-plane sapphire. Exposing c-sapphire substrates to alkali metal halide salts such as KI or NaCl together with the Mo precursor prior to the start of the growth process results in increasing the lateral dimensions of single crystalline domains by more than 2 orders of magnitude. The MoS2 grown this way exhibits high crystallinity and optoelectronic quality comparable to single-crystal MoS2 produced by conventional chemical vapor deposition methods. The presence of alkali metal halides suppresses the nucleation and enhances enlargement of domains while resulting in chemically pure MoS2 after transfer. Field-effect measurements in polymer electrolyte-gated devices result in promising electron mobility values close to 100 cm2 V–1 s–1 at cryogenic temperatures.

Wrinkle-Free Single-Crystal Graphene Wafer Grown on Strain-Engineered Substrates

Abstract: Wrinkles are ubiquitous for graphene films grown on various substrates by chemical vapor deposition at high temperature due to the strain induced by thermal mismatch between the graphene and substrates, which greatly degrades the extraordinary properties of graphene. Here we show that the wrinkle formation of graphene grown on Cu substrates is strongly dependent on the crystallographic orientations. Wrinkle-free single-crystal graphene was grown on a wafer-scale twin-boundary-free single-crystal Cu(111) thin film fabricated on sapphire substrate through strain engineering. The wrinkle-free feature of graphene originated from the relatively small thermal expansion of the Cu(111) thin film substrate and the relatively strong interfacial coupling between Cu(111) and graphene, based on the strain analyses as well as molecular dynamics simulations. Moreover, we demonstrated the transfer of an ultraflat graphene film onto target substrates from the reusable single-crystal Cu(111)/sapphire growth substrate. The wrinkle-free graphene shows enhanced electrical mobility compared to graphene with wrinkles.

Substrate-induced strain and charge doping in CVD-grown monolayer MoS2

Abstract: Due to its electronic-grade quality and potential for scalability, two-dimensional (2D) MoS2 synthesized by chemical vapor deposition (CVD) has been widely explored for electronic/optoelectronic applications. As 2D MoS2 can be considered a 100% surface, its unique intrinsic properties are inevitably altered by the substrate upon which it is grown. However, systematic studies of substrate-layer interactions in CVD-grown MoS2 are lacking. In this study, we have analyzed built-in strain and charge doping using Raman and photoluminescence spectroscopy in 2D MoS2 grown by CVD on four unique substrates: SiO2/Si, sapphire, Muscovite mica, and hexagonal boron nitride. We observed decreasing strain and charge doping in grown MoS2 as the substrates become less rough and more chemically inert. The possible origin of strain was investigated through atomic force microscopy roughness measurements of the as-grown layer and substrate. Our results provide direction for device optimization through careful selection of the ...

Optical and Electronic Properties of Two-Dimensional Layered Materials

Abstract: Modern semiconductor devices have revolutionized wide-ranging technologies such as electronics, lighting, solar energy, and communication [1]. The semiconductor industry employs Si to fabricate electronic circuits, and GaAs, GaN, and other III–V materials for optoelectronics [2], with typical substrates consisting of wafers manufactured at high temperature. Precisely controlled thin films can be deposited on the substrate to achieve additional functionality, for example by chemical vapor deposition (CVD) or molecular beam epitaxy [3].

2D Crystals Significantly Enhance the Performance of a Working Fuel Cell

Abstract: 2D atomic crystals such as single layer graphene (SLG) and hexagonal boron nitride (hBN) have been shown to be “unexpectedly permeable” to hydrogen ions under ambient conditions with the proton conductivity rising exponentially with temperature. Here, the first successful addition of SLG made by a chemical vapor deposition (CVD) method is shown to an operational direct methanol fuel cell significantly enhancing the performance of the cell once the temperature is raised above 60 °C, the temperature at which the proton conductivity of SLG is higher than the Nafion membrane on which it is mounted. Above this temperature, the resistance to proton transport of the system is not affected by the graphene but the barrier properties of graphene inhibit methanol crossover. The performance of the fuel cell is shown to increase linearly with coverage of SLG above this temperature. Results show that the maximum power density is increased at 70 °C by 45% in comparison to the standard membrane electrode assembly without graphene. In addition, a membrane with CVD hBN shows enhanced performance across the entire temperature range due to better proton conductivity at lower temperatures.

Ion bombardment induced buried lateral growth: the key mechanism for the synthesis of single crystal diamond wafers.

Abstract: A detailed mechanism for heteroepitaxial diamond nucleation under ion bombardment in a microwave plasma enhanced chemical vapour deposition setup on the single crystal surface of iridium is presented. The novel mechanism of Ion Bombardment Induced Buried Lateral Growth (IBI-BLG) is based on the ion bombardment induced formation and lateral spread of epitaxial diamond within a ~1 nm thick carbon layer. Starting from one single primary nucleation event the buried epitaxial island can expand laterally over distances of several microns. During this epitaxial lateral growth typically thousands of isolated secondary nuclei are generated continuously. The unique process is so far only observed on iridium surfaces. It is shown that a diamond single crystal with a diameter of ~90 mm and a weight of 155 carat can be grown from such a carbon film which initially consisted of 2 · 1013 individual grains.

Centimeter-Scale CVD Growth of Highly Crystalline Single-Layer MoS2 Film with Spatial Homogeneity and the Visualization of Grain Boundaries

Abstract: MoS2 monolayer attracts considerable attention due to its semiconducting nature with a direct bandgap which can be tuned by various approaches. Yet a controllable and low-cost method to produce large-scale, high-quality, and uniform MoS2 monolayer continuous film, which is of crucial importance for practical applications and optical measurements, remains a great challenge. Most previously reported MoS2 monolayer films had limited crystalline sizes, and the high density of grain boundaries inside the films greatly affected the electrical properties. Herein, we demonstrate that highly crystalline MoS2 monolayer film with spatial size up to centimeters can be obtained via a facile chemical vapor deposition method with solid-phase precursors. This growth strategy contains selected precursor and controlled diffusion rate, giving rise to the high quality of the film. The well-defined grain boundaries inside the continuous film, which are invisible under an optical microscope, can be clearly detected in photolum...

Synthesis Methods of Two-Dimensional MoS2: A Brief Review

Abstract: Molybdenum disulfide (MoS2) is one of the most important two-dimensional materials after graphene. Monolayer MoS2 has a direct bandgap (1.9 eV) and is potentially suitable for post-silicon electronics. Among all atomically thin semiconductors, MoS2's synthesis techniques are more developed. Here, we review the recent developments in the synthesis of hexagonal MoS2, where they are categorized into top-down and bottom-up approaches. Micromechanical exfoliation is convenient for beginners and basic research. Liquid phase exfoliation and solutions for chemical processes are cheap and suitable for large-scale production; yielding materials mostly in powders with different shapes, sizes and layer numbers. MoS2 films on a substrate targeting high-end nanoelectronic applications can be produced by chemical vapor deposition, compatible with the semiconductor industry. Usually, metal catalysts are unnecessary. Unlike graphene, the transfer of atomic layers is omitted. We especially emphasize the recent advances in metalorganic chemical vapor deposition and atomic layer deposition, where gaseous precursors are used. These processes grow MoS2 with the smallest building-blocks, naturally promising higher quality and controllability. Most likely, this will be an important direction in the field. Nevertheless, today none of those methods reproducibly produces MoS2 with competitive quality. There is a long way to go for MoS2 in real-life electronic device applications.

Superhydrophobic Copper Surfaces with Anticorrosion Properties Fabricated by Solventless CVD Methods

Abstract: Due to continuous miniaturization and increasing number of electrical components in electronics, copper interconnections have become critical for the design of 3D integrated circuits. However, corrosion attack on the copper metal can affect the electronic performance of the material. Superhydrophobic coatings are a commonly used strategy to prevent this undesired effect. In this work, a solventless two-steps process was developed to fabricate superhydrophobic copper surfaces using chemical vapor deposition (CVD) methods. The superhydrophobic state was achieved through the design of a hierarchical structure, combining micro-/nanoscale domains. In the first step, O2- and Ar-plasma etchings were performed on the copper substrate to generate microroughness. Afterward, a conformal copolymer, 1H,1H,2H,2H-perfluorodecyl acrylate-ethylene glycol diacrylate [p(PFDA-co-EGDA)], was deposited on top of the metal via initiated CVD (iCVD) to lower the surface energy of the surface. The copolymer topography exhibited a very characteristic and unique nanoworm-like structure. The combination of the nanofeatures of the polymer with the microroughness of the copper led to achievement of the superhydrophobic state. AFM, SEM, and XPS were used to characterize the evolution in topography and chemical composition during the CVD processes. The modified copper showed water contact angles as high as 163° and hysteresis as low as 1°. The coating withstood exposure to aggressive media for extended periods of time. Tafel analysis was used to compare the corrosion rates between bare and modified copper. Results indicated that iCVD-coated copper corrodes 3 orders of magnitude slower than untreated copper. The surface modification process yielded repeatable and robust superhydrophobic coatings with remarkable anticorrosion properties.

Edge-Enriched 2D MoS2 Thin Films Grown by Chemical Vapor Deposition for Enhanced Catalytic Performance

Abstract: Chemical vapor deposition (CVD) is used to grow thin films of 2D MoS2 with nanostructure for catalytic applications in the hydrogen evolution reaction (HER). Tailoring of the CVD parameters results in an optimized MoS2 structure for the HER that consists of large MoS2 platelets with smaller layered MoS2 sheets growing off it in a perpendicular direction, which increases the total number of edge sites within a given geometric area. A surface area to geometric area ratio of up to ∼340 is achieved, benefiting from the edge-exposed high-porosity network structure. The optimized thickness of the MoS2 film is determined for maximum performance, revealing that increasing thickness leads to increased impedance of the MoS2 film and reduced current density. The current density of the optimum sample reaches as high as 60 mA/cm2geo (normalized by geometric area) at an overpotential of 0.64 V vs RHE (in 0.5 M H2SO4), with a corresponding Tafel slope of ∼90 mV/dec and exchange current density of 23 μA/cm2geo. The lower...

Ultrafast Growth of High-Quality Monolayer WSe2 on Au

Abstract: The ultrafast growth of high-quality uniform monolayer WSe2 is reported with a growth rate of ≈26 µm s-1 by chemical vapor deposition on reusable Au substrate, which is ≈2-3 orders of magnitude faster than those of most 2D transition metal dichalcogenides grown on nonmetal substrates. Such ultrafast growth allows for the fabrication of millimeter-size single-crystal WSe2 domains in ≈30 s and large-area continuous films in ≈60 s. Importantly, the ultrafast grown WSe2 shows excellent crystal quality and extraordinary electrical performance comparable to those of the mechanically exfoliated samples, with a high mobility up to ≈143 cm2 V-1 s-1 and ON/OFF ratio up to 9 × 106 at room temperature. Density functional theory calculations reveal that the ultrafast growth of WSe2 is due to the small energy barriers and exothermic characteristic for the diffusion and attachment of W and Se on the edges of WSe2 on Au substrate.

Chemical Vapor Deposition Growth of Linked Carbon Monolayers with Acetylenic Scaffoldings on Silver Foil.

Abstract: Graphdiyne analogs, linked carbon monolayers with acetylenic scaffoldings, are fabricated by adopting low-temperature chemical vapor deposition which provides a route for the synthesis of two-dimensional carbon materials via molecular building blocks. The electrical conductivity of the as-grown films can reach up to 6.72 S cm-1 . Moreover, the films show potential as promising substrates for fluorescence suppressing and Raman advancement.

Synthesis of large-scale atomic-layer SnS 2 through chemical vapor deposition

Abstract: Two-dimensional layers of metal dichalcogenides have attracted much attention because of their ultrathin thickness and potential applications in electronics and optoelectronics. Monolayer SnS2, with a band gap of ~2.6 eV, has an octahedral lattice made of two atomic layers of sulfur and one atomic layer of tin. Till date, there have been limited reports on the growth of large-scale and high quality SnS2 atomic layers and the investigation of their properties as a semiconductor. Here, we report the chemical vapor deposition (CVD) growth of atomic-layer SnS2 with a large crystal size and uniformity. In addition, the number of layers can be changed from a monolayer to few layers and to bulk by changing the growth time. Scanning transmission electron microscopy was used to analyze the atomic structure and demonstrate the 2H stacking poly-type of different layers. The resultant SnS2 crystals is used as a photodetector with external quantum efficiency as high as 150%, suggesting promise for optoelectronic applications.