CVD Method Research Articles

Highly-improved microwave absorption performance of LaFeO3/Fe@CNTs nanocomposites through in-situ synthesis of Fe@CNTs

In order to enhance the microwave absorption performance, the multi-phase nanocomposites composed of magnetic medium and carbon nanotubes (CNTs) is designed and developed based on impedance matching. In this paper, LaFeO3/Fe@CNTs nanocomposites are prepared in situ using LaFeO3 as catalysts and C2H2 as carbon sources with CVD method, and then the microstructures, magnetic properties and microwave absorption performance are investigated in detail. The specific surface area of LaFeO3/Fe@CNTs nanocomposites increases greatly from 16.39 m3/g for LFC0 to 52.29 m3/g for LFC5 with the increasing CNTs content due to the enhanced heterogeneous interfaces. Ms also increases from 0.68 emu/g for LFC0 to 10.24 emu/g for LFC5 from magnetic Fe nanoparticles. LFC5 exhibits the best microwave absorption properties with the minimum reflection loss of -38.758 dB and a broad effective absorption bandwidth of 2.32 GHz at 2.5 mm. Impedance matching is balanced by permittivity from CNTs and permeability from Fe nanoparticles. Owing to the conductive CNTs with more defects, the dielectric loss and eddy current loss both increases to some extent. The synergistic loss mechanism of magnetic Fe nanoparticles and dielectric CNTs result in impedance matching and outstanding microwave attenuation.

Application of Graphene in Acoustoelectronics.

An interdigital transducer structure was fabricated from multilayer graphene on the surface of the YZ-cut of a LiNbO3 ferroelectric crystal. The multilayer graphene was prepared by CVD method and transferred onto the surface of the LiNbO3 substrate. The properties of the multilayer graphene film were studied by Raman spectroscopy. A multilayer graphene (MLG) interdigital transducer (IDT) structure for surface acoustic wave (SAW) excitation with a wavelength of Λ=60 μm was fabricated on the surface of the LiNbO3 crystal using electron beam lithography (EBL) and plasma chemical etching. The amplitude-frequency response of the SAW delay time line was measured. The process of SAW excitation by graphene IDT was visualized by scanning electron microscopy. It was demonstrated that the increase in the SAW velocity using graphene was related to the minimization of the IDT mass.

Development of the Ge-MDST instrument structure with an induced p-type channel

The conditions for the growth of n-type Ge conduction layers by the HW CVD method with the parameters required to create a Ge-TIR transistor with an induced p-type channel are determined. The conditions of deposition by electron beam deposition and subsequent annealing of layers of a high-k dielectric ZrO2:Y2O3 are optimized, allowing to achieve a leakage current of 5 × 10–6 A/cm2. For the developed instrument structure, some parameters of the Ge-TIR transistor were calculated, such as the channel length, the maximum voltage between the drain and the source, and the breakdown voltage.

Maximizing efficiency in C45 steel machining: an integrated AI-based approach to coated insert optimization

AbstractMachining involves the subtraction of the material from the sample workpiece to achieve the desired shape or surface. This versatile method is capable of producing a wide range of parts, varying from simple to intricate profiles. Coating materials are increasingly being utilized in tool inserts in the production industry owing to their superior thermal properties and wear resistance. The shielding of hard coatings, with thicknesses of only a few microns, enhances performance and durability. In this study, machining of C45 steel using distinct coated inserts was explored. The experimental trials employed PVD and CVD methods for coated tungsten carbide (WC) tools/inserts and PVD-coated cermet tools/inserts with different machining parameters. Performance metrics, such as the surface finish and reliability of the tool, were considered for the evaluation. The average tool life variation between the PVD-coated cermet and PVD-coated WC was 178.86%, and 30.11% between the PVD-coated cermet and CVD-coated WC at 1 mm DOC. ANOVA was performed using Response Surface Methodology to explore the influence of input parameters on output. The results indicate that the depth of machining and spindle speed significantly influence Ra, whereas spindle speed and type of tool insert have a considerable impact on the life span of the tool. The developed mathematical model for the prediction of tool life and Ra indicates its potential for performance forecasting during C45 steel machining. Grey relation analysis was employed to optimize the process parameters. Optimal results were achieved with a spindle speed of 400 m/min, 0.5 mm depth of cut, and cermet tool inserts. PVD-coated WC inserts performed better. ANFIS was applied for the prediction and optimization of the machining parameters.

Synthesis of manganese oxide thin films deposited on different substrates via atmospheric pressure-CVD

In this study, we report the synthesis of manganese oxide (MnxOy) thin films on stainless steel, silicon, and borosilicate glass substrates via atmospheric pressure chemical vapor deposition (AP-CVD) using Mn(thd)3 and O3 as precursor and reactive gas, respectively. Deposition was achieved at a low temperature of 300 °C under atmospheric pressure, offering a cost-effective and scalable alternative to traditional high-vacuum CVD methods. The films displayed excellent adhesion and reproducibility, with substrate-dependent variations in film coloration, crystal phases, and morphology. X-ray diffraction (XRD) and Raman spectroscopy confirmed the presence of Mn3O4 and Mn2O3 phases, with Mn3O4 predominating on stainless steel and silicon, while Mn2O3 was more prominent on glass. Scanning electron microscopy (SEM) revealed granular structures with uniform grain sizes, particularly on stainless steel substrates. X-ray photoelectron spectroscopy (XPS) confirmed Mn2+ and Mn3+ oxidation states, consistent with the phase distribution observed by XRD and Raman analysis. This work demonstrates the potential of AP-CVD for scalable manganese oxide thin-film synthesis, particularly for energy storage applications, where Mn3O4 and Mn2O3 can serve as precursors to δ-MnO2 in supercapacitors. The method's simplicity, combined with the high-quality films produced, makes it a promising approach for future research and industrial-scale applications.

Influence of preparation conditions on CsCu2I3 yellow luminescent films based on CVD method

Influence of preparation conditions on CsCu2I3 yellow luminescent films based on CVD method

Enhanced growth rates of N-type phosphorus-doped polycrystalline diamond via in-liquid microwave plasma CVD

Phosphorus-doped diamond (PDD) exhibits excellent properties, making it suitable for a wide range of applications, such as electronic devices and electrodes. Here, we report the first synthesis of PDD by in-liquid microwave plasma CVD (IL-MPCVD) under high-pressure and low-power conditions. A mixture of methanol (MeOH) and ethanol (EtOH) with triethyl phosphate ((C2H5)3PO4) and (P/C = 1000 ppm) was used for the PDD deposition. Samples were characterized by laser microscopy, Raman spectroscopy, and glow discharge optical emission spectroscopy. Notably, PDD was successfully produced at a growth rate of 280 μm/h, which is two orders of magnitude higher than conventional CVD methods. Additionally, cyclic voltammetry (CV) and impedance spectroscopy (EIS) were used to evaluate the electrochemical properties of PDD. As a result, we confirmed the wide potential window characteristic of conductive diamond and determined that the donor density was [P] = 3.8 × 1017cm⁻³. Therefore, it is clear that IL-MPCVD is applicable for very high growth rates in the CVD process for PDD synthesis.

Structure Investigation of highly porous bioceramics based on biogenic hydroxyapatite with graphene oxide coating

Highly porous bioceramics (porosity equal to 93–94 %) based on biogenic hydroxyapatite and sodiumborosilicate glass (40wt% of glass) was prepared by foam replication method at 700 °C and coated by graphene oxide using CVD method. Obtained bioceramics samples were studied by SEM, XRD and Raman spectroscopy. Phase composition, morphology, skeleton density, porosity and compression strength were evaluated. It was shown that biogenic hydroxyapatite in highly-porous bioceramics composition is stable and keeps hydroxyapatite phase without secondary phase formation after sintering with sodiumborosilicate glass as well as after application of CVD method for graphene oxide coating. Formation of graphene oxide for coated bioceramics was confirmed by XRD, SEM and Raman spectroscopy. Significant effect of graphene oxide coating on the porosity and skeleton density was not detected due to thin layer and low content of graphene oxide, but it allows 30 % increasing the compression strength of highly porous bioceramics.

Enhancing photoluminescence of monolayer MoS2 on h-BN substrate through plasmonic resonance for high-power optoelectronic devices

Abstract Hexagonal boron nitride (h-BN) is an excellent substrate material due to its superb thermal conductivity, excellent thermal stability and smooth surface qualities. In this study, a silicon-based h-BN substrate was prepared using the magnetron sputtering technique. Subsequently, monolayer MoS2 obtained by the CVD method was transferred onto the h-BN substrate. Then, Au-core-Ag-shell nanoparticles with a diameter of 80 nm were prepared by a self-assembly method and uniformly dispersed and spin-coated on the MoS2 surface. Applying a laser with a wavelength of 532 nm can effectively excite the plasma resonance effect of the system. Under the intense thermal effect induced by the high laser power and plasma effect, the h-BN substrate ensures that MoS2 exhibits less red-shift and higher photoluminescence intensity compared with SiO2 substrate due to its excellent thermal conductivity. This means that h-BN substrates are particularly suitable for optoelectronic applications under high laser power environments, and can maintain excellent optoelectronic device performance while effectively curbing overheating to ensure long-term stable device operation.

Development of a hydrogen permselective silica membrane and its application to the thermochemical water splitting method

Abstract The thermochemical water splitting IS process is one of the hydrogen production method to use a heat directly. The temperature of the thermal decomposition of water (4000 K) can be reduced under 700 K by introducing I2 and SO2 as recycling catalysts. One of the problems in the IS process is that the conversion of the HI decomposition reaction is low at about 20%. If a membrane reactor with the H2 permselective membrane is applied to the HI decomposition reaction, the hydrogen can be extracted to improve the HI conversion. We focus on a counter diffusion CVD method for the preparation method of the membranes. Two reactants (e.g. silica precursor and oxidant) are provided at the opposite side of the porous substrates and hybrid silica is deposited inside the pore of the substrate. The pore sizes are controlled by introducing organic functional groups to silica precursor. In this study, the silica hybrid membrane with high H2 permeation performance and high H2/HI selectivity were developed by introducing organic functional groups. Effects of the organic functional groups were summarized by using a pore model. The HI gas and other inorganic gases permeation performance were tested through silica hybrid membranes.

Vertical tellurium nano-tower arrays: Topological shape engineering to excellent field emission and optical performance

Vertically aligned tellurium nano-towers (TNTs) building blocks comprising sharp edges have been attained by Au assisted controlled CVD method. The density, size and novel TNTs structures have been optimized in a comprehensive systematic way. The measured base diameter of the TNTs is nearly 150 nm which slowly decreases towards their tip (∼20 nm) in the form of steps realizing their sharp edges. The high density growth of TNTs is estimated to be approximately 2.5 × 108mm2. The two prominent binding energy peaks of TNTs positioned at 583.8 eV and 573.6 eV in XPS graphs are credited to Te-3d3/2 and Te-3d5/2 states of Te along with their XRD lattice parameters a = 4.14 Å and c = 5.25 Å. Owing to distinctive morphology of TNTs which is supportive to easy electron emission, have displayed incredible low turn-on value (3.15 Vμm−1 with excellent stability, exhibiting insignificant (<5 %) FE current fluctuation for 120 min. The intense photoluminescence (PL) peaks displayed by TNTs at 368 nm and comparatively weak shoulder peak at 428 nm (2.897 eV) evidences their potential application in light emitting devices (LEDs). Hence, the incredible PL properties and exclusive FE characteristics revealed by unique TNTs provides the potential applications in opto-electronics and FE display devices.

Evaluation of the effect of oxygen addition on charge carrier transport properties in single-crystal diamond growth

The effects of oxygen addition during single-crystal diamond growth by microwave plasma CVD method on crystal surface morphology and charge carrier transport properties were evaluated. Diamond single-crystals were homoepitaxially grown on (001) surface of high-pressure and high-temperature (HPHT) synthesized type IIa single-crystal diamond substrates with a fixed methane concentration of 1 % and oxygen concentrations of 0–0.8 %. Inverted pyramid-shaped pits were generated as the oxygen concentration increased. The free exciton recombination emission intensity in the cathodoluminescence spectrum reached a maximum at oxygen concentration of 0.5 %. The samples with oxygen concentrations of 0.5 % and 0.8 % showed excellent charge collection efficiency and energy resolution. On the other hand, the mobility-lifetime (μτ) product was only (7.1 ± 1.7) × 10−5 cm2/V, which is approximately 1/4 of that of the sample with 0.2 % methane and no oxygen addition.

Synthesis of InAl-alloyed Ga2O3 nanowires for self-powered ultraviolet detectors by a CVD method.

Ga2O3 is a kind of wide-band gap semiconductor, which has great potential in deep ultraviolet detection because of its high efficiency and fast response. Doping can improve the photoelectric properties of Ga2O3 materials. In this paper, In and Al elements alloyed Ga2O3 nanowires (InAl-Ga2O3 NWs) were successfully grown on p-GaN using a cost-effective chemical vapor deposition method and a vertical structure. The GaN/InAl-Ga2O3 NWs p-n self-powered wide-gap UV photodetector (PD) was constructed based on sputtered gold film as the bottom and top electrodes, and spin coated with polymethyl methacrylate as the insulating layer in the vertical direction. The GaN/InAl-Ga2O3 UV PD exhibits excellent performances, including an extremely low dark current of 0.015 nA, a maximum photocurrent of about 16 nA at zero-bias voltage under 265 nm illumination, and a light-to-dark current ratio greater than 103. The responsivity is 0.94 mA W-1, the specific detectivity is 9.63 × 109 jones, and the good fast response/attenuation time is 31.2/69.6 ms. The self-powered characteristics are derived from the internal electric field formed between p-type GaN and n-type InAl-Ga2O3 NWs, which is conducive to the rapid separation and transfer of photogenerated carriers. This work provides an innovative mechanism of high-performance metal oxide nanowires for the application of p-n junction photodetectors, which can operate without any external bias.

Fabrication of device equipped with rope-like axon bundles by diamond-like carbon thin film patterning deposition

The aim of this research is to fabricate plane-type devices possessing straight longer axons individually and regularly arrayed for evaluating the axon behavior of neuronal cells in vitro toward the development of brain-on-chip models, utilizing diamond-like carbon (DLC) thin film patterning deposition. The DLC thin films were deposited on a polydimethylsiloxane (PDMS) plate with a plasma CVD method under four conditions, with/without stretching of and a metal mask on the plate, and the fabricated substrates were used to culture human neuroblastoma cells, SH-SY5Y, for up to 21 days. In the case of the stretched PDMS plate with the mask covered, extremely peculiar structures were created on the DLC deposited areas of the substrate, with multiple 20 μm-thick rope-like axons aligned straight at the length of millimeter-level at intervals of about 200 μm. It was found that the rope-like axons consisted of plenty of thinner axons, and were supported by the clusters of cells at both ends. It was strongly suggested that the linear wrinkle structures created by the DLC deposition played an important role in the formation of the rope-like axons. This device can be fabricated by means of not conventional lithographic techniques, but only DLC thin film deposition.

Ultra‐low power consumption flexible sensing electronics by dendritic bilayer MoS2

AbstractTwo‐dimensional transition metal dichalcogenides (2D TMDs) are promising as sensing materials for flexible electronics and wearable systems in artificial intelligence, tele‐medicine, and internet of things (IoT). Currently, the study of 2D TMDs‐based flexible strain sensors mainly focuses on improving the performance of sensitivity, response, detection resolution, cyclic stability, and so on. There are few reports on power consumption despite that it is of significant importance for wearable electronic systems. It is still challenging to effectively reduce the power consumption for prolonging the endurance of electronic systems. Herein, we propose a novel approach to realize ultra‐low power consumption strain sensors by reducing the contact resistance between metal electrodes and 2D MoS2. A dendritic bilayer MoS2 has been designed and synthesized by a modified CVD method. Large‐area edge contact has been introduced in the dendritic MoS2, resulting in decreased the contact resistance significantly. The contact resistance can be down to 5.4 kΩ μm, which is two orders of magnitude lower than the conventional MoS2 devices. We fabricate a flexible strain sensor, exhibiting superior sensitivity in detecting strains with high resolution (0.04%) and an ultra‐low power consumption (33.0 pW). This study paves the way for future wearable and flexible sensing electronics with high sensitivity and ultra‐low power consumption.image

Research on iron removal on carbon nanotube materials synthesized by the CVD method using 2,4-D adsorption in aqueous solution

In this study, the technique of oxidation in air and treatment with HCl was chosen to remove iron in carbon nanotube materials synthesized by the CVD method to apply 2,4-D adsorption in aqueous solution at initial concentration 52.2 mg/L. The oxidation process was repeated twice at 440 ˚C for 4 hours and 40 minutes, respectively. XRD, TEM, BET, AAS, HPLC analysis methods have shown that the MWCNTs tube tips are open and not shortened, can handle 94.42 % Fe, removing Fe has increased the surface area. BET alone increased from 170 to 262 m2/g and pore volume increased from 0.897 to 1.402 cm3/g, increasing the adsorption capacity of the material from 64.39 to 80.16 %.

Manufacture of a Nanocomposite of Carbon Fibre and Nanotubes and Epoxy Resin

Nanocomposite material have been manufactured by the manual contact method, using nanotubes and carbon fibres as the basis for manufacturing the nanocomposite and epoxy resin as the matrix. The CVD method was used to manufacture the carbon nanotubes on the carbon fibre with twill and plain weaves. Additionally, the mechanical properties of the nanocomposite with twill and plain weave were obtained from the tensile tests, and the density was obtained experimentally. The carbon nanotubes, CNTs, grew perpendicular to the surface of the carbon fibres, CF. The average diameter was 117 μm and the average length was 23.87 μm. The nanocomposite made of carbon nanotubes, carbon fibre and epoxy resin, CNT/CF/Epoxy with single layer twill weave had a thickness of 0.57 mm, while the plain weave nanocomposite had 0.56 mm. The densities obtained of the CNT/CF/Epoxy material were 1.03 g/cm3 with the plain weave and 1.08 g/cm3 with the twill weave. While the densities of the composite material, CF/Epoxy, where 1.21 g/cm3 and 1.19 g/cm3 with plain and twill weave. The densities of the CNT/CF/Epoxy were 14.28% and 9.14% lower than the densities of the CF/Epoxy, both with the plain and twill weave. From the tensile tests the mechanical properties obtained of the CNT/CF/Epoxy with twill weave were a modulus of elasticity of 31 GPa and a maximum stress of 153.47 MPa and with the plain weave the modulus of elasticity was 25.10 GPa and the maximum stress was 121.71 MPa. Both composite and nanocomposite materials were investigated with twill weave, and it was found that the best results of the mechanical properties were obtained with the nanocomposite, the increase of the modulus of elasticity and the maximum stress were 23.82% and 2.16% respectively.

Broken crystal symmetry of MWCNTs as the key factor in improvement of carboxyl functionalization

Carbon nanotubes functionalized with carboxyl groups (COOH-CNTs) find their application in energy storage, sensing, improving mechanical stability and biomedicine. So a facilitation of COOH-groups bonding to CNTs is one the modern scientific challenges. In this study untreated multi-walled CNT (MWCNTs), nitrogen-doped MWCNT (N-MWCNTs) and ion-beam irradiated N-MWCNTs (irr-N-MWCNTs) were synthesized using the CVD method. Characterizations were performed via HRTEM, Raman, XPS, and NEXAFS spectroscopy. Irr-N-MWCNTs demonstrated the largest amount of carbon crystallites, the presence of Stone-Wales defects as well as the regions of tensile-compressive, shear and torsional deformation. All these factors contributed to increase of carboxyl functionalization at the tube’s surface. On the base of experimental data, the atomic supercells of N-MWCNTs and irr-N-MWCNTs were built by the self-consistent-charge density-functional tight-binding method (SCC DFTB). Through SCC DFTB, we quantified atomic rearrangements, electronic structures, charge transfers, total energies, and the forces and energy barriers relevant to COOH bonding. The twisting of irr-N-MWCNTs supercells by 45 degrees decreased the barrier to the carboxyl formation in 2.5 times in comparison to undeformed nanotubes. Our findings reveal that nitrogen addition, ion-beam irradiation, and induced deformations create the necessary conditions for COOH functionalization by altering the physicochemical surface properties of MWCNTs.

Memristor characteristics of a Ga–Al–O/Ga–Sn–O/Ga–Al–O stack device fabricated using mist chemical vapor deposition

The biological human brain-mimicking neuromorphic computing systems have drawn great attention recently. Synaptic elements of the neuromorphic computing systems are required to have high integration capability, low power consumption, and low cost. We have realized a memristor characteristic of a Ga–Al–O/Ga–Sn–O/Ga–Al–O stack device using mist-CVD (mist CVD). The mist CVD method is a thin film fabrication technology with a safe, simple equipment configuration, and low-cost environmental impact. It is achieved that hysteresis I–V curves of memristor characteristics were certainly obtained, and electric resistance for the high resistance state and the low resistance state were stably repeated at least 500 times. The results suggest a possibility that Ga–Sn–O thin films by mist CVD methods can be a key component of neuromorphic computing systems.

Comparative analysis: CapEx in diamond mining versus diamond growing, based on open data sources and experimental results

The diamond industry has long been associated with environmental and social problems, ranging from mining practices to ethical concerns related to diamond sourcing. In recent years, there has been a growing interest in lab-grown diamonds as a sustainable alternative for diamond consumers. However, the production of lab-grown diamonds has own challenges. This article examines the capital expenditures per annualized carat of rough diamonds obtained through mining and two fabrication methods: high-pressure high-temperature (HPHT) and microwave plasma-assisted chemical vapour deposition (MP CVD). Lab-grown diamonds produced using HPHT and MP CVD methods require significantly higher capital expenditures per annualized carat compare to mined diamonds. HPHT diamonds require on-time CapEx of 500–833 US$ per carat annually, while MP CVD diamonds demand 549–1648 US$ per carat annually. Finding ways to reduce production cost and increase efficiency will be crucial in realizing the potential of lab-grown diamonds as a sustainable alternative to mined diamonds.