Chemical Vapor Deposition Method Research Articles

Enhanced highly bismuth‐doped multicomponent phosphate glass fibers for broadband amplifiers

AbstractBismuth (Bi)‐doped glass fibers are being developed into next‐generation broadband amplifiers and tunable lasers. Yet, the well‐developed Bi‐doped fiber devices only realize silica‐based optical fibers prepared by the modified chemical vapor deposition method, which faces challenges such as low doping concentration, high cost, intricate device structure, and high preparation difficulty. Here, a novel highly Bi‐doped multicomponent phosphate glass was developed. The high ion solubility of this phosphate glass facilitates achieving a Bi doping concentration of 8 mol%. The introduction of aluminum nitride (a new reducing agent) can create a local reducing environment, further increasing the concentration of low‐valence near‐infrared (NIR) active Bi ions. Furthermore, the resulting enhanced highly Bi‐doped multicomponent phosphate glass with efficient 900–1600 nm NIR emission can be drawn into corresponding optical fibers by a rod‐in‐tube method. Broadband NIR amplified spontaneous emission with a 3 dB bandwidth of 275 nm was achieved in this new fiber. As far as we know, this is the first successful preparation of Bi‐doped multicomponent phosphate glass fiber. Our results indicate that this fiber will be a powerful alternative to Bi‐doped silica‐based fibers for the preparation of related Bi‐doped fiber devices.

Atomic-Thin WS2 Kirigami for Bidirectional Polarization Detection.

The assembly and patterning engineering in two-dimensional (2D) materials hold importance for chip-level designs incorporating multifunctional detectors. At present, the patterning and stacking methods of 2D materials inevitably introduce impurity instability and functional limitations. Here, the space-confined chemical vapor deposition method is employed to achieve state-of-the-art kirigami structures of self-assembled WS2, featuring various layer combinations and stacking configurations. With this technique as a foundation, the WS2 nano-kirigami is integrated with metasurface design, achieving a photodetector with bidirectional polarization-sensitive detection capability in the infrared spectrum. Nano-kirigami can eliminate some of the uncontrollable factors in the processing of 2D material devices, providing a freely designed platform for chip-level multifunctional detection across multiple modules.

Catalytic particles formation from thin nickel films for the synthesis of multi-walled carbon nanotubes

We have investigated the formation of a catalyst for the synthesis of multi-walled carbon nanotubes (MWCNT) using nickel-on-titanium thin films. Nickel decomposes into nanoparticles in the synthesis setup prior to MWCNT growing through the plasma enhanced chemical vapor deposition method. Oxidation and reduction of the catalyst are conducted to control the morphology of the formed nanoparticles array. In this case, the redox treatments required preventing the formation of silicides and Ti–Ni alloys are combined with the well-known effect of low-temperature disintegration (dewetting) of thin films. Detailed studies using a combination of Auger, atomic force, scanning (SEM), and transmission electron microscopy (TEM) show the interaction of metals on a silicon substrate, the influence of treatments parameters on the catalyst's state. The features and morphology of MWCNT synthesized on the obtained catalysts were studied via Raman spectroscopy, SEM and TEM. Overall, showing a link between the catalyst formation process and MWCNT growth, we demonstrate a technological and versatile method for controlling of nanotube growth for various applications.

Hydrophilic modification of feed spacer and its impacts on antifouling performance of reverse osmosis membrane

AbstractFeed spacers improve mixing and mass transfer in membrane modules. However, they also lead to foulant deposition in the vicinity of the spacer surface. In this paper, two hydrophilic monomers, namely, acrylic acid (AA) and 2‐hydroxyethyl methacrylate (HEMA), are respectively coated on the surface of a commercial feed spacer via a plasma‐enhanced chemical vapor deposition (PECVD) method. The resulting modified spacers are then evaluated alongside with a reverse osmosis (RO) membrane for its solute rejection, water permeability, and antifouling properties. Results show that the surface hydrophilicity of feed spacers has been enhanced upon the AA and HEMA deposition. During filtration test, the HEMA‐modified spacer demonstrates higher flux recovery rate (94.17%) and salt rejection (95.78%) for the RO membrane. In contrast, the membrane with the unmodified spacer only shows 89.44% and 92.46%, respectively. Additionally, the membrane with the HEMA‐modified spacer has a thinner fouling layer (200 nm) compared to the unmodified spacer (700 nm). The HEMA‐coated spacer outperforms all the tested spacers, demonstrating that feed spacer modification with a hydrophilic monomer via the PECVD method can effectively reduce membrane fouling.

Development of Self-Doped Monolayered 2D MoS2 for Enhanced Photoresponsivity.

Transition metal dichalcogenides (TMDs) exist in two distinct phases: the thermodynamically stable trigonal prismatic (2H) and the metastable octahedral (1T) phase. Phase engineering has emerged as a potent technique for enhancing the performance of TMDs in optoelectronics applications. Nevertheless, understanding the mechanism of phase transition in TMDs and achieving large-area synthesis of phase-controlled TMDs continue to pose significant challenges. This study presents the synthesis of large-area monolayered 2H-MoS2 and mixed-phase 1T/2H-MoS2 by controlling the growth temperature in the chemical vapor deposition (CVD) method without use of a catalyst. The field-effect transistors (FETs) devices fabricated with 1T/2H-MoS2 mixed-phase show an on/off ratio of 107. Photo response devices fabricated with 1T/2H-MoS2 mixed-phase show ≈55 times enhancement in responsivity (from 0.32 to 17.4AW-1) and 102 times increase in the detectivity (from 4.1×1010 to 2.48×1012cmHzW-1) compare to 2H-MoS2. Introducing the metallic 1T phase within the 2H phase contributes additional carriers to the material, which prevents the electron-hole recombination and thereby increases the carrier density in the 1T/2H-MoS2 mixed-phase in comparison to 2H-MoS2. This work provides insights into the self-doping effects of 1T phase in 2H MoS2, enabling the tuning of 2D TMDs properties for optoelectronic applications.

Spectroscopic analysis of pulsed-mode plasma with argon addition for diamond growth

The advancement of high-speed growth technology for large-scale single-crystal diamonds is desired. In the widely used microwave plasma chemical vapor deposition method, the gas temperature in the plasma atmosphere significantly contributes to the generation of reactive radicals and enhancement of crystal growth. However, the impact of electron-dominated reactions in the plasma on the crystal growth remains unclear. In this study, we actively controlled the plasma environment by adding argon gas and adopting microwave pulse modulation to generate the plasma. We estimated the gas temperature and electron density of the plasma using optical emission spectroscopy. Our results implied that an increase in gas temperature alone hardly explained the enhancement of the growth rate by the argon addition or pulse modulation. In addition to the increase in the electron density due to the argon addition and pulse modulation, gas-phase chemical reaction calculations showed that the radical production enhancement became remarkable under an electron density higher than a threshold (1017 m−3). Therefore, the enhancement of the growth rate mentioned above may be attributed to electron-dominated reactions in the discharge region. These findings suggest that increasing the electron density can further improve the growth rate and potentially enable diamond synthesis at lower temperatures than traditional methods.

5 MeV Si ion irradiation effects on structural and morphological properties of multiwalled carbon nanotubes

Carbon based nanomaterials (CBNs) such as multi walled carbon nanotubes (MWCNTs), graphene etc have attracted huge interest due to their widespread applications in contemporary nanotechnology. The ion bombardment is an important method which can be used for tuning of the structural and morphological properties of the CBNs. In the present work, we have carried out ion irradiation on MWCNTs (prepared by chemical vapour deposition method) with 5 MeV Si ions at different fluences ranging from 1 × 1014 to 5 × 1016 ions/cm2. The resulting structural and morphological modifications on the pristine MWCNTs have been characterized by using X-ray diffraction, Raman spectroscopy and field emission scanning electron microscopy. Results observed after successful characterization are compared with pristine sample results and we observed that the irradiation creates defects in MWCNTs and causes amorphized carbon nanomaterials depending on the fluence and energy deposited by energetic ions inside the MWCNTs.

Watt-level cladding-pumped bismuth-doped fiber laser operating near 1.31 [formula omitted]m

We report, to the best of our knowledge, the first CW bismuth-doped fiber laser operating at around 1.31 μm with an output power of >1 W utilizing a cladding-pumping configuration with multimode semiconductor laser diodes emitting at a wavelength of 793 nm. The Bi-doped fiber (BDF) serving as an active medium of the laser was based on a pedestal-index design, where P2O5−SiO2 glass core surrounded by P-doped cladding. The BDF construction offers advanced gain characteristics and an increased mode size (∼13 μm). The fiber preform was fabricated by the conventional modified chemical vapor deposition (MCVD) method combined with all gas-phase doping technique. The BDF with low-index polymer coating provided sufficient cladding peak absorption at 750 nm belonging to bismuth active centers associated with phosphorus atoms (BACs-P) that allowed to develop a continuous-wave laser with a linear cavity configuration and enable a maximum slope efficiency of ∼ 4% with respect to the absorbed pump power. In addition, near-field spatial intensity distribution of optical beam has good quality (M2<1.13) and close to Gaussian mode profile in x and y directions. The perspectives for optimization of BDF design and laser system configurations based on such fibers for further power scaling are discussed.

Fabricating Large-Area Thin Films of 2D Conductive Metal-Organic Frameworks.

ConspectusRecent years have witnessed significant interest in two-dimensional metal-organic frameworks (MOFs) due to their unique properties and promising applications across various fields. These materials offer distinct advantages, including high porosity and excellent charge transport properties. Their tunability allows precise control over various factors, including the electronic structure adjustments and local reactivity modulation, facilitating a wide range of properties and applications, such as material sensing and spin dynamics control. Moreover, the precise crystal structure of 2D MOFs supports rational design and mechanism studies, providing insights into their potential applications and enhancing their utility in various scientific and technological endeavors.To fully unveil the latent capabilities of 2D MOFs and advance their applications across diverse fields, thin film synthesis is crucial. Thin films provide a platform for investigating the intrinsic electrical properties of 2D MOFs with anisotropic structures, enabling the exploration of their unique characteristics comprehensively. Additionally, thin films offer the advantage of minimizing interference at contacts and junctions, thereby enhancing the performance of 2D MOFs for various applications. Furthermore, the properties of thin films can vary with thickness, presenting an opportunity to tailor their characteristics based on specific requirements.In this Account, we present an overview of our research focusing on the synthesis of 2D conductive MOF thin films encompassing two primary methods: chemical vapor deposition and solution processing. The chemical vapor deposition method allows for one-step, all-vapor-phase processes resulting in MOFs with edge-on orientation, controllable film thicknesses ranging from 55 to 662.7 nm, and smooth, homogeneous surfaces. On the other hand, solution-processing introduces a novel MOF, Cu3(HHTATP)2, by reducing interlayer interactions through the addition of pendent Brønsted bases on a ligand, enabling spin coating for thin film synthesis. This method yields a concentrated 2D MOF solution, enabling spin coating for thin film synthesis, where reversible electrical conductivity changes occur through doping with an acid and dedoping with a base. Additionally, we discuss various other synthesis methods, such as interfacial synthesis, layer-by-layer assembly, and microfluidic-assisted synthesis, offering versatile approaches for fabricating large-area thin films with tailored properties. Finally, we address ongoing challenges and potential strategies for further advancement in 2D conductive MOF thin film synthesis. We hope that this Account provides insights for selecting synthesis methods tailored to specific purposes, contributes to the development of varied synthesis techniques, and facilitates the exploration of diverse applications, unlocking the full potential of 2D conductive MOFs for next-generation technologies.

Superhydrophobic Stainless Steel Mesh through Chemical Vapour Deposition of TMCS for Effective Oil-Water Separation

Aim: To Fabricate the superhydrophobic Stainless Steel (SS) mesh using Trimethylchlorosilane (TMCS) through a Chemical Vapor Deposition (CVD) method for the oil-water mixture separation Background: The frequent oil spills have a devastating impact on marine ecosystems and the environment. The porous materials with superhydrophobic properties have been created to separate oil and water effectively. Due to their ability to effectively separate oil and water, superhydrophobic coatings have gained significant attention. Methods: The cleaned stainless-steel mesh was put on a stand and covered with a glass container. Within the container, 50 mL of hexane, which contained 1 mL of TMCS, was added. The mesh was then left for 3 h to undergo the CVD process Results: The silane content with low surface energy creates a highly rough structure on the mesh surface. The optimal mesh coating is superhydrophobic, having a strong affinity to oil and a water contact angle of 162 ± 2°. The coated mesh has shown a separation efficiency of over 97.8% for different oil-water mixtures. The coatings sustain their superhydrophobicity up to 30 tape peels and 40 times sandpaper abrasion, indicating good mechanical durability. Conclusion: The study concludes that the S-3 sample is mechanically stable and can withstand various tests such as adhesive tape peeling, sandpaper abrasion, bending, folding, and twisting. It efficiently separates oil and water mixtures on a large scale with high efficacy

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.

High responsive Pd decorated low temperature α-MoO3 hydrogen gas sensor

The H2 gas adsorption properties, which are the most crucial concept for a gas sensor, of the 2-dimensional (2D) MoS2 are limited compared to its oxide form of 2D α-MoO3. On the other hand, it is straightforward to form high surface-to-volume ratio nanostructures with MoS2. In order to get the benefits of the large surface and better H2 adsorption properties for the H2 gas sensor, MoS2 film grown by the chemical vapor deposition (CVD) method was converted into MoO3 with a thermal oxidation process at 380 °C under oxygen-ambient conditions. The grown MoS2 film has indicated that it is formed from the coalesced MoS2 flakes. An ultra-high response of 3 × 106 at a relatively low temperature of 100 °C was achieved for as low as 800 ppm hydrogen concentration. The hydrogen gas sensing mechanism has been discussed in depth using the double injection model, similar to the electrochromic mechanism.

Effects of Plasma Ions/Radicals on Kinetic Interactions in Nanowall Deposition: A Review

Recent advances in the growth of carbon nanowalls (CNWs) and vertical graphene nanosheets using various plasma‐enhanced chemical vapor deposition (PECVD) methods are reviewed in this article. Growth methods are classified into hot‐ and cold‐wall reactors equipped with diverse plasma generation systems, and their respective characteristics are summarized, with particular attention to the behavior of reactive species, such as ions and radicals, generated within the plasma. Recent progress in this research domain is outlined for each method, and an organized account of the chemical kinetic phenomena occurring within the plasma is provided. Finally, future perspectives are discussed. Fundamental data are obtained through real‐time in situ measurements of ions and radicals, and the construction of a database from these data offers microscopic insights that significantly enhance processing outcomes for macroscopically controlling the mechanical shapes and chemical properties of CNWs.

Enhancing and broadening the photoresponse of CdS nanowire by constructing core–shell heterostructure

Limited by the severe surface recombination and large bandgap, it is still a challenge to achieve a high-performance broad-spectrum photodetector based on CdS nanowires (NWs). In this work, the CdS/GeS core–shell heterostructure is constructed to enhance and broaden the photoresponse of CdS NWs. The CdS/GeS core–shell heterostructure NWs are prepared by the chemical vapor deposition method, exhibiting smooth surfaces, controlled shell thicknesses, and compositions. From the UV-Vis-near-infrared (NIR) diffuse reflectance spectrum, PL, and time-resolved photoluminescence studies, it is found that the surface recombination is weakened and the light absorption range is widened after the constructing core–shell heterostructure. When configured into photodetectors, the responsivity of the CdS/GeS core–shell heterostructure NWs is up to 76.8 A W−1, which is 10 folds higher than that of pristine CdS NWs. Furthermore, the photoresponse wavelength of the CdS/GeS core–shell heterostructure NWs is extended from 405 to 850 nm. The improved photodetection performance is attributed to the effective separation of photogenerated carriers at the heterostructure interface, weakened surface recombination, and excellent light absorption of the GeS shell. All results imply that constructing core–shell heterostructures is an effective strategy for constructing high-performance photodetectors.

Preparation and Electrical Performance Analysis of a GaAs‐Based Tritium Battery

A nuclear battery is a promising candidate for small power supply sources in the military and commercial fields, but its output power and energy conversion efficiency need to be improved. This paper mainly describes a design, preparation, and electrical performance analysis of a GaAs-based tritium battery. The design of the tritium battery uses a multistage process with Monte Carlo and Matlab simulations. A titanium tritide source was prepared by a high-temperature tritium absorption device, and a GaAs semiconductor transducer was developed using a metal-organic chemical vapor deposition method. The D/Ti ratio and T/Ti ratio of the deuterium/tritium titanium films were 1.9 and 1.7, respectively. Two kinds of GaAs-based PIN junction semiconductor transducers were proposed and irradiated with the prepared tritium source. Their electrical properties were measured in situ and analyzed qualitatively. Under the irradiation of a 0.61-Ci tritium source, the short-circuit current of the device was 0.3 to 0.38 μA, the open-circuit voltage was 35 to 63 mV, the peak power was 2.8 to 6.4 nW, and the energy conversion efficiency of the GaAs semiconductor transducer was about 1.86%. It was found that an air gap between the GaAs semiconductor transducer and the radioactive source caused serious loss of beta particle energy, resulting in low output power and low energy conversion efficiency of the nuclear battery. The open-circuit voltage of the devices with a SiO2 passivation layer on the surface decreased both in a dark environment and in light illumination, but SiO2 passivation did not reduce surface recombination as expected. The research work in this paper will provide some valuable reference for the preparation and performance optimization of nuclear batteries.

The Effects of Some Factors on the Electrical Properties of Cu2O/ZnO Double Films Fabricated by Chemical Vapor Deposition Method

The Effects of Some Factors on the Electrical Properties of Cu2O/ZnO Double Films Fabricated by Chemical Vapor Deposition Method

Superwetting PVA/cellulose aerogel with asymmetric structure for oil/water separation and solar-driven seawater desalination

Extracting clean water from oily wastewater and seawater is one of the effective strategies to alleviate the freshwater crisis. However, achieving both high separation efficiency and excellent salt resistance remain challenges for materials. Herein, a novel methyltrichlorosilane-modified polyvinyl alcohol/cellulose aerogel (MPCA) was prepared by freeze drying, chemical cross-linking, and chemical vapor deposition (CVD) methods. The superwetting MPCA presented an asymmetric structure, in which the small dense pores at the top surface facilitated the efficient separation of water-in-oil (W/O) emulsions and the large pores on the bottom surface were beneficial for brine exchange. The as-prepared superwetting aerogel was suitable for the separation of various W/O emulsions with excellent separation flux (631.9–2368.7 L·m−2·h−1) and outstanding separation efficiency (99.5 %). In addition, MPCA achieved a high evaporation efficiency of 1.39 kg·m−2·h−1 and a satisfactory energy conversion efficiency of 89.7 %. Moreover, the unique asymmetric structure endowed the evaporator excellent salt resistance and could self-dissolve the accumulated salt in 20 min. The as-prepared MPCA could achieve efficient W/O emulsion separation as well as produce freshwater in seawater, providing a new strategy for oily waste seawater purification.

Simultaneous purification and oxidation of the as-synthesized MWCNTs with KMnO4 using phase transfer catalyst at three different pH medium by the hydrothermal method

Improving and streamlining current oxidation techniques for experimental is the main goal of the research described in the present article. By applying the pressure created while on the hydrothermal process to an autoclave walled with Teflon, simplifying the procedure was accomplished. By comparing the degrees of functionalization attained with the dispersibility in the substantially pure and functionalized multi-walled carbon nanotubes (MWCNTs) final product, the beneficial effect of the procedure was evaluated. In order to achieve this, the study looked at and investigated how as-synthesized MWCNTs from Fe-Mo/MgO catalyst were simultaneously purified and oxidized using the chemical vapor deposition (CVD) method. Aliquot-336 was used as phase transfer catalyst (PTC) by hydrothermal method under three different pH conditions. Following functionalization, nanotubes of carbon might easily combine with various chemical reagents to generate homogeneous dispersions or even well-aligned structures because of the functional groups linked to their surfaces. In this case, a chemical called reagent potassium permanganate (KMnO4) is necessary in order to target particular π-bonds while entirely destroying the nanotubes' graphene structures. The techniques have been explained in terms of mechanism, and the Fourier transform-infrared (FT-IR) spectroscopy has confirmed the functionalizations of the CNTs. These approaches were further explored through FT-Raman spectrum analysis, thermal assessments, energy dispersive X-ray spectroscopy (EDX), TEM (transmission electron microscopy) along with the help of EDX, and visible-near IR absorption and UV–visible absorption spectroscopy (ABS) procedures.

Numerical Investigation on Thermal Conductivity of Graphene Foam Composite for Thermal Management Applications.

Graphene foam prepared by the chemical vapor deposition method is a promising thermal interfacial material. However, the thermal properties of graphene foam highly depend on the experimental fabrication conditions during the chemical vapor deposition process. Aiming to reveal how to prepare the appropriate graphene foam for the various thermal management scenarios, the influence of experimental conditions on thermal properties of graphene foam was investigated. Furthermore, the contribution of thermal conductivity and thermal radiation to the effective thermal coefficient of graphene foam was carried out for comparison. The research results showed that the porosity and the cross-section shape of the struts of the growth template were two critical factors affecting the thermal transport of graphene foam, especially with the increase of temperature. In addition, the deposition time of graphene determined the wall thickness and affected the thermal conductivity directly. The thermal radiation contributed more than thermal conductivity when the temperature climbed continuously. Comparatively, the effective thermal coefficient of graphene foam composite with high porosity and circular-shape struts was much superior to that of others at high temperature. The research findings provide important guidance for graphene foam fabrication and its applications in the field of thermal management.

Electrochemical activity of self-supporting nitrogen-doped graphene for the degradation and in-situ determination of methylene blue

Environmentally friendly wastewater treatment and online pollution monitoring systems, important for water quality control, are yet to be developed. Electrochemical strategies combining the electrocatalytic degradation and electroanalysis of organic pollutants are expected to achieve this key technology. This study employed a chemical vapor deposition method using N₂ gas as the nitrogen source and applying an alternating electric field to prepare self-supporting nitrogen-doped graphene (NG) tubes with a wall thickness of up to 480 μm comprising few-layer NG nanosheets. The correlation between the properties of these materials and the electrocatalytic activity for methylene blue (MB) was investigated. The feasibility of the electrochemical strategy for online wastewater treatment and detection was validated using a combination of UV–visible spectroscopy and differential pulse voltammetry. The NG tube with the N-C bond distribution regulated by adjusting the methane flow rate and growth time exhibited high electrocatalytic activity, rapidly degrading 50 mg L⁻¹ of MB within 36 min and tracking changes in MB concentration. The NG tubes were assembled in an electrocatalytic meter pen for water treatment, achieving a degradation efficiency of 99.4 % and a detection limit of 0.3 mg L−1 for the MB solution, quite satisfactory for emerging simultaneous degradation and monitoring processes. The developed self-supporting NG tubes are promising materials for electrocatalytic degradation anodes and sensing electrodes in water treatment. Dual-functional electrocatalytic systems have potential applications in water quality monitoring and improvement.