Chemical Vapor Deposition Method Research Articles

Stoichiometry modulated tunable optoelectronic properties of Nb-doped WS2 synthesized by chemical vapor deposition method.

Significant progress has been made in the field of two-dimensional WS2, yet the precise control of the doping process to achieve desired properties and the interpretation of complex physical phenomena in these novel materials necessitate thorough research. In this study, Nb-doped WS2 is synthesized using chemical vapor deposition technology, leading to triangular flakes with a side length of 12-20μm. The X-ray photoelectron spectroscopy analysis indicates that the NbW substitution defect functions as an electron acceptor. The interlayer and transverse forces of the Nb-doped WS2 flake approach 1 nN and 150 pN, respectively. As the doping concentration increases, the valence band maximum energy of Nb-doped WS2 ranges from 4.06eV to 4.3eV. Furthermore, the performance of the photodetector is discussed.

All‐Paper‐Based, Flexible, and Bio‐Degradable Pressure Sensor with High Moisture Tolerance and Breathability Through Conformally Surface Coating

AbstractHighlighted with bio‐degradability, paper‐based flexible pressure sensors receive significant attention in the field of wearable devices for a sustainable future. However, it remains a challenge to possess considerable sensing performance in high humidity and underwater environments, because its structure rapidly breaks down after the hydrophilic cellulose absorbs water. In this study, a facile chemical vapor deposition method is employed to conformally coat a thin hydrophobic layer onto the cellulose fibers, resulting in an encapsulating paper with high moisture tolerance. The well‐maintained porous structure reserves the superior breathability of the paper. A micro‐convex‐structured sensor layer impregnated with MXene serves as the sensing layer. As a result, an all‐paper‐based pressure sensor with high moisture tolerance and breathability is fabricated. This sensor features a broad sensing range (0–60 kPa), acceptable sensitivities (39.58 kPa−1 (0–1.01 kPa), 11.95 kPa−1 (1.01–60 kPa)), a low detection limit of ≈2.8 Pa, response and recovery time (93 and 69 ms), reliable hydrophobic breathability, and excellent repeatability (10 000 cycles). Moreover, this sensor can be safely worn on human skin and can monitor physiological signals in real‐time in different environments (including air, humid environments, and even underwater), providing a reliable, economical, and environmentally friendly solution for wearable technology.

Unveiling high-temperature stability and growth dynamics of CVD-SiOC coatings across different deposition conditions and environments

Abstract In this study, we systematically investigated the high-temperature protection performance and evolution behavior of three different SiOC coatings (1050SiOC, 1100SiOC, 1150SiOC) under different atmospheres. The coatings were prepared by the organometallic chemical vapor deposition (CVD) method and characterized using scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS) techniques. It was found that the composition and microstructure of SiOC coatings, environmental atmosphere, and heat treatment temperature can affect the thermal stability and high-temperature reaction mechanism of SiOC coatings. Further, it was revealed that the three SiOC coatings only exhibit the same high-temperature evolution behavior and reaction mechanism in an air environment while exhibiting different high-temperature evolution behavior and reaction mechanisms in both an inert atmosphere and a reduced air atmosphere. Among the coatings prepared, the 1050SiOC coating demonstrated the highest on-set oxidation temperature under identical oxygen content conditions. This characteristic may contribute to the coating’s excellent resistance to high-temperature oxidation.

Phase-Selective Synthesis of Rhombohedral WS2 Multilayers by Confined-Space Hybrid Metal-Organic Chemical Vapor Deposition.

Rhombohedral polytype transition metal dichalcogenide (TMDC) multilayers exhibit non-centrosymmetric interlayer stacking, which yields intriguing properties such as ferroelectricity, a large second-order susceptibility coefficient χ(2), giant valley coherence, and a bulk photovoltaic effect. These properties have spurred significant interest in developing phase-selective growth methods for multilayer rhombohedral TMDC films. Here, we report a confined-space, hybrid metal-organic chemical vapor deposition method that preferentially grows 3R-WS2 multilayer films with thickness up to 130 nm. We confirm the 3R stacking structure via polarization-resolved second-harmonic generation characterization and the 3-fold symmetry revealed by anisotropic H2O2 etching. The multilayer 3R WS2 shows a dendritic morphology, which is indicative of diffusion-limited growth. Multilayer regions with large, stepped terraces enable layer-resolved evaluation of the optical properties of 3R-WS2 via Raman, photoluminescence, and differential reflectance spectroscopy. These measurements confirm the interfacial quality and suggest ferroelectric modification of the exciton energies.

Controlled growth of high-quality β-Ag2Se nanowires and their applications in near-infrared photodetection

This work reports the controlled growth of single-crystalline β-Ag2Se nanowires and their application in near-infrared photodetection. High-quality Ag2Se nanowires with an orthorhombic crystal structure are grown via the chemical vapor deposition method with a length up to 32.8 μm and a diameter down to 52.1nm. By fine-tuning the growth parameters such as total tube inner pressure and precursor temperature, the length of Ag2Se nanowires can be precisely controlled. A dynamic growth model is also introduced to interpret the growth mechanism of Ag2Se nanowires. Two-terminal photodetectors based on single Ag2Se nanowire are fabricated and show competitive photodetection performance compared to that of other silver chalcogenide nanomaterial-based photodetectors. At room temperature, the fabricated Ag2Se nanowire-based photodetector exhibits a broadband response range of 400 - 1064nm at a bias voltage of 2V, while the peak photo-response performance is obtained in the near-infrared region. Under 830nm light illumination, the maximum responsivity, specific detectivity, rise time and decay time are measured and calculated to be 99.6mA/W and 4.01 × 106 Jones, 23.84 ms and 47.6 ms, respectively, demonstrating its potential in uncooled near-infrared photodetector applications.

Lyophilization Strategy to Synthesize Ultrafine NaCl Template for Preparation of Photocatalytic BiOCl Nanoplates via Chemical Vapor Deposition

Two-dimensional (2D) bismuth oxychloride (BiOCl) has attracted increasing attention in nanoelectronics, catalysis, energy storage, and the environment, attributed to its wide indirect band gap and large surface area. However, the imprecise control of the catalytic site on the substrate makes it challenging to produce 2D BiOCl in large quantities economically. Here, we developed lyophilization to create ultrafine NaCl templates to obtain a higher yield of 2D BiOCl nanoplates than traditional substrates using a chemical vapor deposition (CVD) method. In contrast to ball milling or recrystallization, lyophilization can produce the sodium chloride (NaCl) in the ice lattice domain, resulting in ultrafine NaCl particles after removing water. Moreover, the NaCl particles synthesized by lyophilization showed lower crystallinity with partially distorted structures, such as twisted octahedral structures and the structure with Na+ separated from other atoms by an ice lattice. In addition, our method offers an opportunity to introduce and engineer the oxygen vacancies (OVs) on 2D BiOCl to narrow the band gap, improve the separation of photogenerated carriers, and enhance their photocatalytic efficiency by 17.2 times. Thus, our work opens a new avenue to produce 2D BiOCl by tuning the substrate in CVD growth and inspires a new strategy to promote the performance of 2D photocatalysts.

Optoelectronic properties of chemical vapor deposition grown monolayer MoS2 nanowires

Monolayer (1 L) MoS2 nanowire possesses large amount of exposed edges, resulting in unique physical properties differing to the large size flake. Preparation of high quality 1 L MoS2 nanowire using chemical vapor deposition (CVD) is still challenging to the best of our knowledge. Herein, by employing space-confined CVD method using Mo foil as Mo source, 1 L MoS2 nanowires with width of ∼70 nm can be deposited on the surface of 1 L MoS2 flake. Tip-enhanced photoluminescence (TEPL) measurements indicate different PL peak position and intensity distribution across the nanowires. Photosensitive Kelvin probe force microscopy (KPFM) measurements further reveal that these nanowires exhibit lower Fermi level than the 1 L MoS2 flake, resulting in tunable optosensitive charge transfer under different excitation photon energies form 1.58 eV to 2.33 eV.

Synthesis and characterization of graphene on copper foil via atmospheric pressure chemical vapor deposition method and its impact on electrical properties

Copper, prized for its exceptional electrical conductivity, thermal conductivity, and mechanical strength, is a staple in electronic applications. The ongoing quest for enhanced performance in miniaturized technologies has led to exploring copper-graphene composites, particularly those integrating bilayer graphene (BLG). This study investigates the enhancement of electrical conductivity in copper through the incorporation of BLG via atmospheric pressure chemical vapor deposition (APCVD). The research highlights the APCVD method's ability to grow high-quality BLG on high-purity oxygen-free copper foil, demonstrating significant improvements in electrical properties. Detailed characterization reveal that the graphene growth process induces structural changes in the copper, promoting ideal crystallographic orientations and larger grain sizes. This process achieves nearly complete graphene coverage and results in a copper/graphene (Cu/GR) composite with minimal defects. The electrical conductivity of the Cu/GR composite significantly increased to 59.32 × 10⁶ S·m⁻1, a 7.83 % improvement over the pristine copper foil. This enhancement is attributed to the increased carrier density and mobility within the composite. These advancements suggest the potential of APCVD-grown graphene for various high-performance electronic applications, providing a promising pathway for further development and optimization of graphene-copper composites.

Ab Initio Kinetic Pathway of Diborane Decomposition on Transition Metal Surfaces in Borophene Chemical Vapor Deposition Growth.

The chemical vapor deposition (CVD) method holds promise for the scalable and controlled synthesis of high-quality borophene. However, the current lack of an atomistic understanding of intricate kinetic pathways from precursors to borophene impedes process optimization. Here, we employ first-principles simulations to systematically explore the pyrolytic decomposition pathways of the most used precursor diborane (B2H6) to borophene on various transition metal surfaces. Our results reveal that B2H6 on various metal substrates exhibits different dissociation behaviors. Meanwhile, the activity of the examined metal substrates is quite anisotropic and surface direction-dependent, where the estimated overall catalytic activity order of these metals is found to be Pd ≈ Pt ≈ Rh > Ir ≈ Ru ≈ Cu > Au ≈ Ag. Our study provides atomistic insights into the dissociation kinetics of diborane precursors on various transition metal surfaces, serving as a guide for experimental growth of borophene.

Magnetic iron-based nanoparticles encapsulated in graphene/reduced graphene oxide: Synthesis, functionalization and cytotoxicity tests

Nanomaterials for suitable particle sizes, shapes, surface properties, biocompatibility, magnetic properties, and chemical stability are candidates for biomedical applications. Among these nanomaterials, iron-based ones are highly interested in their morphological and magnetic properties for potential utilizations in biomedicine. However, iron-based nanoparticles lose their chemical stability in body fluids because of their oxide formations and transformations. Their use in biomedical applications, especially in imaging, may be less effective if they are oxidized and have lower magnetization values. Thus, the idea of coating them with a protective layer has recently emerged to prevent magnetic nanoparticles from degrading in human fluids and losing their magnetic properties. However, the biological effects of these coated nanoparticles on human cells are poorly understood. In this paper, the synthesis of multilayer graphene (MLG) encapsulated iron-based nanoparticles was investigated by solvothermal and chemical vapor deposition (CVD) methods followed by purification. Subsequently, their surface modification was conducted with pyrene end-functional POEGMA obtained by atom transfer radical polymerization (ATRP). Cytotoxicities of synthesized nanoparticles were evaluated in MCF7 cell lines, which is a commonly used model for breast cancer research. We also compare the results with those obtained from bare iron oxide nanoparticles (IONPs) and iron oxides that were embedded in reduced graphene oxide (rGO) or partially coated with it. We aim to evaluate the safety and efficiency of these nanoparticles and increase their chemical stability as a multifunctional nano platform for cancer diagnosis and treatment. Characterization techniques such as XRD, XPS, SEM, TEM, DTA/TG, DLS, zeta potential, BET, NMR, FTIR, and VSM were performed on the nanoparticles. Cytotoxicity assessments on MCF-7 cell lines indicated the potential of these graphene-based magnetic nanoparticles for biomedical applications, particularly drug delivery, due to their small size, soft ferromagnetic properties, high chemical stability, and cytocompatibility at concentrations below 500 μg/mL over short incubation times.

Wafer scale and substrate-agnostic growth of MoS2 nanowalls for efficient electrocatalytic hydrogen generation in acidic and alkaline media

Emerging as a promising alternative to expensive platinum-based catalysts for electrocatalytic hydrogen evolution reaction (HER), molybdenum disulfide (MoS2) stands out for its favourable thermodynamic properties. However, the catalytic activity of MoS2 is mostly confined to its edges while the basal plane remains inactive, limiting practical applicability. Fabrication of stable MoS2 structures with enhanced active sites on a given surface area still remains a complex task. Here we introduce a substrate-agnostic, metal-organic chemical vapour deposition (MOCVD) method for large-area 3D dendritic nanostructures of 2D MoS2, termed as “MoS2 nanowalls”. Using scanning and transmission electron microscopy (SEM/TEM), we elucidate the growth mechanism of the MoS2 nanowalls and their branched dendritic structure. Even subjected to extreme pH environments (0 and 14) during the HER, the grown MoS2 nanowalls show remarkable stability even after >170 hours of continuous operation and exhibit excellent catalytic activity with 10 mAcm−2 current density achievable by applying low overpotentials (309±2 mV at pH = 0 and 272±2 mV at pH = 14). The presented large-area growth method for inexpensive MoS2 nanowall based catalyst can pave the way for practical applications of water electrolysis cells operating at low voltages (≤1.5 V).

Accurate comparison of the fracture toughness of ultra-thick polycrystalline diamond plates by ISO standard method

Due to the difficulty in preparing ultra thick diamonds, current research on the mechanical properties of diamonds mostly focuses on thin samples, which cannot represent the true mechanical properties. In this study, DC arc plasma jet chemical vapour deposition method was used to deposit ultra-thick diamond plate measuring Ø125 mm × 6.5 mm. The size of 18 mm × 4 mm × 3 mm sample were prepared. The samples with dimensions of 18 mm × 4 mm × 3 mm were prepared. For the first time, fracture toughness test samples meeting the ISO 15732 requirements were prepared by using the single-sided beam pre-crack method. The accurate fracture toughness of ultra-thick diamond with pre-crack was obtained using the three-point bending method, 6.5 MPa·m1/2. Samples with sharp or blunt notch by laser cutting were used for comparison. The sharp notch sample had a value similar to that of the pre-crack sample, 6.3 MPa·m1/2. The value of the blunt notch sample was relatively large, 7.5 MPa·m1/2. The effects of defects and grain size on fracture toughness and the reasons for the differences in test results for different notches were analyzed. Overall, obtaining accurate fracture toughness values of ultra-thick diamond by ISO standard is crucial for industrial applications.

MgOMo2C/multiwalled carbon nanotube composite for high-performance supercapacitor applications

Magnesium molybdate (MgMoO4) nanostructure has been successfully prepared and employed as a catalyst for the production of multi-walled carbon nanotubes (CNTs) by the chemical vapor deposition method. The prepared nanostructure materials are characterized through XRD, TEM, FTIR, BET and Raman spectroscopy. The XRD results and TEM images confirm the formation of the plate-like MgMoO4 structure, as well as the existence of Mo2C and CNTs in the type of bundles structure (CNTBs). The high dispersion and stability of Mo nanoparticles in the composite of plate-like MgMoO4 is responsible for the formation of CNTBs with uniform diameters. Thus, the plate-like MgMoO4 nanoparticles and the MgOMo2C@CNTBs hybrid material are assessed as electrodes in a supercapacitor device for the first time. The produced hybrid supercapacitor MgOMo2C@CNTBs has a good specific capacitance (354 F g−1) and strong cycling stability (82 percent capacity retention over 2000 cycles)

Mass production and cutting performance of diamond coated cutting tools for machining titanium alloys

Diamond coated cutting tools are applied for machining difficult-to-machine materials of titanium alloys. However, the temperature field uniformity needs to be further improved for the mass production of diamond coated tools using the hot filament chemical vapor deposition (HFCVD) method. In this paper, the tools temperature distribution is simulated by the finite volume method (FVM) during the deposition of diamond coatings. An optimization method of deposition setting with fine filaments in dense arrangement (FFDA) is proposed, and the temperature distributions of the tools under the coarse filament in sparse arrangement (CFSA) and FFDA are simulated to systematically elucidate the effects of fine filament densification. Subsequently, the different hot filament arrangements are adopted to mass production experiment for deposition of micro/nano composite diamond (MCD/NCD) coatings on WC-6%Co cutting tools. In addition, the cutting experiments on titanium alloys are conducted using diamond coated tools, and the cutting performance of tools at different locations is evaluated. The results indicate that the FFDA method can improve the temperature field uniformity of mass-produced diamond coated cutting tools, and the cutting tools have better consistency in surface morphology, thickness, chemical composition, surface roughness and cutting performance.

Strong and Tough Multilayer Heterogeneous Pyrocarbon Based Composites

AbstractThe integration of bio‐inspired hierarchical design into synthetic carbon materials holds promise for developing lightweight, high‐performance structural materials. Hierarchical and heterogeneous nanoscale units are crucial to load bearing and mechanical functionality yet receives limited attention for difficulties in accurate regulation. Herein, one kind of multilayered heterogeneous have proposed pyrocarbon based composite constructed through chemical vapor deposition method with nanoscale graphene orderliness regulation. Sequential construction from orientational graphene sheets to nondirective isotropic networks is achieved through controlling the size and morphology of pyrolysis intermediates with moderate oxidation, being expected to facilitate load transfer and structural stability through dynamically adjustment in heterogeneous interfacial sliding. The resulting multilayer heterogeneous phases exhibit impressive strengthening and toughening mechanisms dominated by microstructural multiscale coupling, which provides new solutions for developing structural composites for high‐temperature aerospace applications. Additionally, the multiple internal reflections arising from the abundant heterogeneous interfaces significantly improve the efficiency of electromagnetic microwave absorption. The multilayered heterogeneous interfaces achieved through orderliness manipulation offer novel insights into the assembly of mechanical functionality integration for wide‐temperature applications and high‐performance macroscopic carbon‐based composites.

Enhanced Raman Scattering in CVD-Grown MoS2/Ag Nanoparticle Hybrids.

Surface-Enhanced Raman Spectroscopy (SERS) is a powerful, non-destructive technique for enhancing molecular spectra, first discovered in 1974. This study investigates the enhancement of Raman signals from single- and few-layer molybdenum disulfide (MoS2) when interacting with silver nanoparticles. We synthesized a MoS2 membrane primarily consisting of monolayers and bilayers through a wet chemical vapor deposition method using metal salts. The silver nanoparticles were either directly grown on the MoS2 membrane or placed beneath it. Raman measurements revealed a significant increase in signal intensity from the MoS2 membrane on the silver nanoparticles, attributed to localized surface plasmon resonances that facilitate SERS. Our results indicate that dichalcogenide/plasmonic systems have promising applications in the semiconductor industry.

Mixed phase iron oxides thin layers by atmospheric-pressure chemical vapor deposition method

This paper provides a simple method for producing a metal oxide thin layer methodology by atmospheric pressure chemical vapor deposition (APCVD) synthesis over stainless steel substrates. This methodology enables the formation of thin iron oxide layers at its performance at various temperatures of 330 °C, 430 °C, and 530 °C. The deposition arises from thermal decomposition of the iron organometallic precursor Fe3(CO)12, forming a thin layer of iron oxide is, by the ozone present in the reaction chamber promoting the deposition of the iron oxide particles over the substrate. The Raman characterization suggest that at 330 °C, a mixture of hematite and magnetite is predominant on the as deposited substrates, also hematite modes show to be more pronounced as the band at 300 cm-1 narrows. Conversely, magnetite is prominent at higher synthesis temperatures, exhibiting a more intense Eg5 mode at 680 cm-1. The particles exhibit a uniform morphology, with both metal oxide phases coexisting. The average diameter of the particles is 50 nanometers as scanning electronic microscopy shows in a transversal sample section.•The formation of particles is attributed to the combination of iron ions +2 and +3 in the deposition process and their interaction with oxygen in the given synthesis parameters at atmospheric pressure chemical vapor deposition (APCVD).

Synthesis and Anisotropic Memristive Behavior of Borophene Nanosheets

Neuromorphic computing, marked by its parallel computational abilities and low power usage, has become pivotal in advancing artificial intelligence. However, the advancement of neuromorphic computing has faced significant obstacles due to the performance limitations of traditional memory devices struggling with high power consumption and limited reliability. Two‐dimensional (2D) materials have been extensively investigated as high‐performance memristive materials, but they are often restricted by fixed memristive properties, which complicate circuit design and limit flexibility. Here, we report that multilayer borophene nanosheets represent a breakthrough material, displaying anisotropic variable memristive properties. The nanosheets, comprising semiconductor α’‐4H‐borophene sheets and metal β12‐borophene sheets, have been synthesized on aluminum foil surface through chemical vapor deposition (CVD) method. The multilayer borophene nanosheets exhibit volatile memory behavior in the vertical direction and non‐volatile memory behavior in the planar direction. This innovative class of 2D nanosheets not only overcomes the limitations of conventional memory devices but also expands the potential applications of borophene‐based memories in information storage and in‐memory computing.

Synthesis and Anisotropic Memristive Behavior of Borophene Nanosheets.

Neuromorphic computing, marked by its parallel computational abilities and low power usage, has become pivotal in advancing artificial intelligence. However, the advancement of neuromorphic computing has faced significant obstacles due to the performance limitations of traditional memory devices struggling with high power consumption and limited reliability. Two-dimensional (2D) materials have been extensively investigated as high-performance memristive materials, but they are often restricted by fixed memristive properties, which complicate circuit design and limit flexibility. Here, we report that multilayer borophene nanosheets represent a breakthrough material, displaying anisotropic variable memristive properties. The nanosheets, comprising semiconductor α'-4H-borophene sheets and metal β12-borophene sheets, have been synthesized on aluminum foil surface through chemical vapor deposition (CVD) method. The multilayer borophene nanosheets exhibit volatile memory behavior in the vertical direction and non-volatile memory behavior in the planar direction. This innovative class of 2D nanosheets not only overcomes the limitations of conventional memory devices but also expands the potential applications of borophene-based memories in information storage and in-memory computing.

INITIATED CHEMICAL VAPOR DEPOSITION (iCVD) OF POLY(ACRYLIC ACID): A COMPARISON BETWEEN CONTINUOUS AND CLOSED-BATCH iCVD APPROACHES

In this study, poly(acrylic acid) (PAA) thin films were deposited on silicon wafer and glass surfaces by initiated chemical vapor deposition (iCVD) method using di-tert-butyl peroxide (TBPO) as the initiator and acrylic acid (AA) as the monomer. During iCVD, two different precursor feeding approaches, namely continuous and closed-batch, were employed. The effects of substrate temperature and the precursor feeding approaches on the deposition rates and surface morphology of the films were investigated. The highest deposition rates for the continuous and closed-batch iCVD approaches were found as 26.1 nm/min and 18.6 nm/min, respectively, at a substrate temperature of 15 °C. FTIR analysis of the films deposited by both approaches indicated high structural retention of the monomer during the polymerization. AFM results indicated that, PAA thin films possessed low RMS roughness values of 2.76 nm and 1.84 nm using continuous and closed-batch iCVD, respectively. Due to the slightly higher surface roughness of the film deposited under continuous iCVD, that film exhibited a lower water contact angle of 16.1° than the film deposited in closed-batch iCVD. In terms of monomer utilization ratio, closed-batch system was found to be more effective, which may help to minimize the carbon footprint of iCVD process.