Chemical Vapor Deposition Furnace Research Articles

The Cu/TiO2 adsorbent modified by Ce-doping removes trace phosphorus impurities from circular hydrogen of a polysilicon chemical vapor deposition furnace

There is an urgent need for efficient and cost-effective adsorbents for the removal of trace hydrogen phosphide (PH3) from the circular hydrogen systems in the polysilicon chemical vapor deposition furnaces. In this study, a straightforward and cost-effective method was used to synthesize a highly efficient adsorbent (Cex-Cuy/TiO2) for PH3 removal using TiO2 as the carrier and CuO as the active substance. Experimental findings demonstrated that optimal Ce doping amounts (nCu:nCe = 20:1) markedly enhanced the adsorbent's performance, with an adsorption capacity reaching as high as 149.14 mg g−1. Material characterization results indicated that Ce positively influenced the uniform dispersion of Cu on the TiO2 surface, and Ce doping increased the adsorbed oxygen content of the adsorbent, consequently enhancing its oxidation performance. The investigation of the reaction mechanism and causes of adsorbent deactivation revealed that the depletion of active substances (CuO) in the adsorbent and the accumulation of products such as Cu3P and phosphates are the primary factors contributing to its deactivation. Furthermore, high-temperature calcination could restore the activity of the adsorbent, indicating its great potential for engineering applications.

Comparing Ultralong Carbon Nanotube Growth from Methane over Mono- and Bi-Metallic Iron Chloride Catalysts.

This research endeavours to study the growth of ultralong carbon nanotubes (UL-CNTs) from methane using diverse catalysts, namely FeCl3, bi-metallic Fe-Cu, Fe-Ni, and Fe-Co chlorides. Aqueous catalyst solutions were evenly dispersed on silica substrates and grown at 950 °C in the presence of hydrogen via a horizontal chemical vapour deposition (CVD) furnace. The samples underwent characterisation by Raman spectroscopy, scanning electron microscopy (SEM), and optical microscopy to identify the quality of CNTs and enumerate individual UL-CNTs. Our findings revealed that FeCl3, as a mono-metallic catalyst, generated the longest UL-CNTs, which measured 1.32 cm, followed by Fe-Cu (0.85 cm), Fe-Co (0.7 cm), and Fe-Ni (0.6 cm), respectively. The G/D ratio (graphene to defects) from the Raman spectroscopy was the highest with the FeCl3 catalyst (3.09), followed by Fe-Cu (2.79), Fe-Co catalyst (2.13), and Fe-Ni (2.52). It indicates that the mono-iron-based catalyst also produces the highest purity CNTs. Moreover, this study scrutinises the vapour-liquid-solid (VLS) model for CNT growth and the impact of carbide formation as a precursor to CNT growth. Our research findings indicate that forming iron carbide (Fe3C) is a crucial transition phase for amorphous carbon transformation to CNTs. Notably, the iron catalyst generated the longest and densest CNTs relative to other iron-based bi-metallic catalysts, which is consistent with the temperature of carbide formation in the mono-metallic system. From correlations made using the phase diagram with carbon, we conclude that CNT growth is favoured because of increased carbon solubility within the mono-metallic catalyst compared to the bi-metallic catalysts.

Recrystallization of MBE‐Grown MoS2 Monolayers Induced by Annealing in a Chemical Vapor Deposition Furnace

A systematic study of MoS2 grown by a combination of physical vapor deposition and post‐growth annealing treatment has been conducted. Hereby, MoS2 thin films with thicknesses between 1 and 2 layers are first grown on sapphire by molecular beam epitaxy at different growth temperatures and then transferred to S environment inside a tube furnace for an annealing process. Depending on the growth temperature, the as‐grown layers are either amorphous or form a crystalline structure composed of closely packed nanometer‐size grains. The annealing process leads to recrystallization of these layers significantly increasing the size of the MoS2 crystalline domains to the range of 50–100 nm. While the originally amorphous layer displays rotational domains after annealing, recrystallization of samples grown at high temperatures yields single crystalline layers. All samples display an increase of the crystallite dimension, which is accompanied by the disappearance of the defect‐related peaks in the Raman spectra, sharpening of the excitonic signatures in absorption, and strong enhancement of the photoluminescence yield. The results represent a promising way to combine advantages of physical vapor deposition and a post‐growth annealing in a chemical vapor deposition furnace toward fabrication of wafer‐scale single crystalline transition metal dichalcogenide mono‐ and multilayer films on non‐van der Waals substrates.

Implementation of SiN thin film in fiber-optic sensor working in telecommunication range of wavelengths

Mirrors are used in optical sensors and measurement setups. This creates a demand for mirrors made of new materials and having various properties tailored to specific applications. In this work, we propose silicon covered with a thin silicon nitride layer as a mirror for near-infrared measurements. SiN layer was deposited on a standard silicon wafer with a Low-Pressure Chemical Vapor Deposition furnace. Then, the created layer was investigated using ellipsometry and scanning electron microscope. Subsequently, the mirror was used as a reflecting surface in a Fabry–Perot fiber-optic interferometer. The mirror performance was investigated for wavelengths used in telecomunication (1310 nm and 1550 nm) and then compared with results obtained with the same measurement setup, with a silver mirror instead of silicon covered with SiN, as reference. Results showed that the proposed mirror can replace the silver one with satisfying results for investigated wavelengths.

Large-area uniform few-layer PtS2: Synthesis, structure and physical properties

At present, the research in field of the transition metal dichalcogenides (TMDs) was mostly concentrated in the group 6 TMDs such as MoS2 and WS2 for numerous applications like optoelectronics, sensing and so on. However, our research focuses on the group 10 of TMDs, which is relatively unexplored. Platinum disulfide (PtS2), a typical representative of the group 10 TMDs, is a newly developed two-dimensional materials with high carrier mobility, widely tunable bandgap, and ambient stability for electronic and optoelectronic applications. Here, we experimentally and theoretically investigate the synthesis, structure and physical properties of the few-layer PtS2. A inch scale of few-layer PtS2 was synthesized by direct sulfurization of Pt metal sputtered on the SiO2/Si substrate in a Plasma Enhanced Chemical Vapor Deposition (PE-CVD) furnace. And the electronic band structure of layered PtS2 was obtained by density function theory (DFT). A series of characterizations including Raman spectroscopy, Photoluminescence (PL), atomic force microscopy (AFM), scanning electron microscope (SEM), high-resolution transmission electron microscope (HR-TEM) and X-ray photoelectron spectroscopy (XPS) have demonstrate the quality and uniformity of the few-layer PtS2 as prepared. Moreover, the field-effect transistor (FET) was fabricated based on PtS2 in order to investigate their electronic properties, which show a p-type semiconductor behavior. Further, the work function and potential difference of the PtS2 on the SiO2/Si substrate were measured by Kelvin probe force microscopy (KPFM), showing 32 meV and 36 mV, respectively. The few-layer PtS2 samples were treated with oxygen plasma to investigate the Raman transforms, exhibiting the reduction of Raman intensity after treatment due to oxidation. The idea that this synthesis strategy can also be applied to other PtX2 devices are speculated to promote the application of TMDs in advanced optoelectronic devices.

Growth of carbon nanotubes on the surface of carbon fiber using Fe–Ni bimetallic catalyst at low temperature

This article provides a method for growing carbon nanotubes(CNTs) on carbon fibers(CFs) using iron and nickel as catalysts at low temperatures. This series of experiments was conducted in a vacuum chemical vapor deposition(CVD)furnace. It is found that Fe–Ni catalysts, which have a certain thickness and can be better combined with resins when manufacturing composite materials, are more ideal for the growth of CNTs than single metal catalysts. At the same time, it is proved that the CVD process worked best at 450 °C. The mechanical property test proved the reinforcing effect of CNTs on carbon fiber, the single-filament tensile strength of CFs obtained by using Fe–Ni catalyst at 450 °C was 11% higher than that of Desized CFs. The bonding strength of carbon fiber and resin has also been significantly improved. When synthesized at low temperature, CNTs exhibited a hollow multi-wall structure.

Germanium-assisted growth of titanium dioxide nanowires for enhanced photocatalytic and electron emission performance

In this study, free-standing and well-aligned titanium dioxide (TiO2) nanowires were grown on a Ti foil by precisely controlling the growth temperature and the thickness of the Ge catalyst layer. The catalyst layer played an important role in activating the surface of the Ti foil, facilitating the growth of TiO2 nanowires on it in a chemical vapor deposition furnace system. The structure of the TiO2 nanowires was investigated using scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The photocatalytic experiment results showed that the optimum Ge catalyst layer thickness significantly improved the rhodamine B (RhB) degradationefficiencyofthe nanowires. The TiO2 nanowires grown using a 40-nm-thick Ge layer could degrade 74% of RhB after 5 h of ultraviolet irradiation. In addition, the TiO2 nanowires exhibited excellent electron field emission performance as compared to the TiO2 nanocrystals grown without the Ge catalyst layer. The results suggested that TiO2 nanowires grown using a Ge catalyst layer are promising materials for next-generation electronic emitters and photocatalytic systems.

Synthesis of High-Quality Monolayer MoS2 by Direct Liquid Injection

We report the synthesis of high-quality single monolayer MoS2 samples using a novel technique that utilizes direct liquid injection (DLI) for delivery of precursors. The DLI system vaporizes a liquid consisting of a selected precursor dissolved in a solvent into small, micron-sized droplets in an expansion chamber maintained at a selected temperature and pressure, before delivery to the deposition chamber. We demonstrate synthesis of monolayer MoS2 on SiO2/Si substrates using the DLI technique with film quality superior to exfoliated samples or those grown by traditional tube furnace chemical vapor deposition (CVD) methods. Photoluminescence measurements of DLI monolayers exhibit consistently brighter emission, narrower line width and higher emission energy than their exfoliated and CVD counterparts. Conductive atomic force microscopy identifies a defect density of 8.3 x 10^11/cm2 in DLI MoS2, lower than the measured density in CVD material and nearly an order of magnitude improvement over the exfoliated MoS2 investigated under the same conditions. The DLI method is directly applicable to many other van der Waals materials which require the use of challenging low vapor pressure precursors, to growth of alloys, and sequential growths of dissimilar materials leading to van der Waals heterostructures.

Evolution of large area TiS2-TiO2 heterostructures and S-doped TiO2 nano-sheets on titanium foils

We report a novel and facile method to synthesize sulfur-doped titanium oxide sheets and realize TiS2-TiO2 heterostructures by means of a sequential sulfurization and oxidation step in a dual-zone chemical vapor deposition furnace. The inclusion of chlorine and argon gases during the growth of such titanium-based compounds plays a critical role in the formation of desired geometries and crystalline structures. These heterostructures possess nano-whisker and nanosheet configurations, controlled by adjusting the growth parameters such as temperature, carrier gas and the sequencing between different steps of the growth. The evolution of these complex heterostructures has been investigated using Raman spectroscopy and EDS characterization. The presence of chlorine gas during the growth results in local TiS2 formation as well as faceted growth of TiO2 nanosheets through anatase to rutile phase change prohibition. The electron microscopy (TEM) images and diffraction pattern (SAED) characterization reveal the crystallinity and layered nature of grown structures, further demonstrating the 2D characteristics of S-doped nanosheets. The evolution of TiO2 on TiS2 heterostructures has also has been verified using XPS analysis. These highly featured nanostructures are suitable candidates to enhance the photocatalytic behavior of TiO2 nanostructures.

Gas-Phase Synthesis for Label-Free Biosensors: Zinc-Oxide Nanowires Functionalized with Gold Nanoparticles

Metal oxide semiconductor nanowires have important applications in label-free biosensing due to their ease of fabrication and ultralow detection limits. Typically, chemical functionalization of the oxide surface is necessary for specific biological analyte detection. We instead demonstrate the use of gas-phase synthesis of gold nanoparticles (Au NPs) to decorate zinc oxide nanowire (ZnO NW) devices for biosensing applications. Uniform ZnO NW devices were fabricated using a vapor-solid-liquid method in a chemical vapor deposition (CVD) furnace. Magnetron-sputtering of a Au target combined with a quadrupole mass filter for cluster size selection was used to deposit Au NPs on the ZnO NWs. Without additional functionalization, we electrically detect DNA binding on the nanowire at sub-nanomolar concentrations and visualize individual DNA strands using atomic force microscopy (AFM). By attaching a DNA aptamer for streptavidin to the biosensor, we detect both streptavidin and the complementary DNA strand at sub-nanomolar concentrations. Au NP decoration also enables sub-nanomolar DNA detection in passivated ZnO NWs that are resilient to dissolution in aqueous solutions. This novel method of biosensor functionalization can be applied to many semiconductor materials for highly sensitive and label-free detection of a wide range of biomolecules.

In-situ continuous growth of carbon nanotubes on the surface of carbon fibres

An efficient method for growing carbon nanotubes (CNTs) on the surface of continuously moving carbon fibres has been developed by a unique open-ended chemical vapor deposition (CVD) furnace. Scanning electron microscopy (SEM) is used to observe the morphological characteristics of CNTs grown on carbon fibre surfaces, and high-resolution transmission electron microscopy (HRTEM) is used to study the microstructure of CNTs. The results show that the CNTs achieve uniform and orderly growth. In the process of CNTs growth, the cross-linking of adjacent graphite crystallites is formed and the damage of the catalyst nanoparticles to the fibres is repaired, so the tensile strength is increased compared to the carbon fibres undergoing reduction. CNTs-grown carbon fibres can be used to fabricate the flexible supercapacitor electrodes to improve electrochemical capacitance and promote electrochemical stability.

Anisotropy of thermal conductivity in In2Se3 nanostructures

In this report, α-In2Se3 single-crystal nanobelts and nanowires were grown in the thermal chemical vapor deposition furnace. The growth direction of the nanobelts was identified by standard microscopy techniques and was along the in-plane direction, while that of the nanowire was along the c-axis. The temperature-dependent thermal conductivity of the nanostructures was measured by a suspended-pattern technique, and it was found to fall into two ranges of values between 300 and 400 K owing to the difference in growth orientation. The experimental evidence presented herein is the anisotropy of phonon transport of the layered α-In2Se3, and the effect of bonding strength on the thermal conductivity at the nanoscale. This study would be helpful to the physical understanding and future design of In2Se3–based thermoelectric materials.

SiNx films and membranes for photonic and MEMS applications

This work presents a novel process to form SiNx films and process for membranes with excellent mechanical properties for micro-electro-mechanical systems application as well as integration as IR waveguide for photonic application. The SiNx films were fabricated in SiNgen apparatus which is a single wafer chamber equipment compared to conventional low pressure chemical vapor deposition furnace process. The films showed low stress, good mechanical properties, but the synthesis also eradicates the issues of particle contamination. Through optimizing of the growth parameters and post annealing profile, low stress (40 Mpa) SiNx film could be finally deposited when annealing temperature rose up to 1150 °C. The stress relaxation is a result of more Si nano-crystalline which was formed during annealing, according to the FTIR results. The mechanical properties, Young’s modulus and hardness, were 210 Gpa and 20 Gpa respectively. For the waveguide application, a stack of three layers, SiO2/SiNx/SiO2 was formed where the optimized layer thicknesses were used for minimum optical loss according to simulation feedback. After deposition of the first two layers in the stack, the samples were annealed in range of 900–1150 °C in order to release the stress. Chemical mechanical polish technique was applied to planarize the nitride layer prior to the oxide cladding layer. Such wafers can be used to bond to Si or Ge to manufacture advanced substrates.

Chemical Vapor Deposition Growth of Large-Area Monolayer MoS2 and Fabrication of Relevant Back-Gated Transistor**Supported by the National Natural Science Foundation of China under Grant No 61774064.

A closed two-temperature-zone chemical vapor deposition (CVD) furnace was used to grow monolayer molybdenum disulfide (MoS2) by optimizing the temperature and thus the evaporation volume of the Mo precursor. The experimental results show that the Mo precursor temperature has a large effect on the size and shape transformation of the monolayer MoS2, and at a lower temperature of <760°C, the size of the triangular MoS2 increases with the elevating temperature, while at a higher temperature of >760°C, the shape starts to change from a triangle to a truncated triangle. A large-area triangular monolayer MoS2 with a side length of 145 μm is achieved at 760°C. Further, the as-grown monolayer MoS2 is used to fabricate back-gated transistors by means of electron beam lithography to evaluate the electrical properties of MoS2 thin films. The MoS2 transistors with monolayer MoS2 grown at 760°C exhibit a high on/off current ratio of 106, a mobility of 1.92 cm2/Vs and a subthreshold swing of 194.6 mV/dec, demonstrating the feasible approach of CVD deposition of monolayer MoS2 and the fabrication of transistors on it.

Strategy for Fabricating Wafer-Scale Platinum Disulfide.

PtS2 is a newly developed group 10 2D layered material with high carrier mobility, wide band gap tunability, strongly bound excitons, symmetrical metallic and magnetic edge states, and ambient stability, making it attractive in nanoelectronic, optoelectronic, and spintronic fields. To the aim of application, a large-scale synthesis is necessary. For transition-metal dichalcogenide (TMD) compounds, a thermally assisted conversion method has been widely used to fabricate wafer-scale thin films. However, PtS2 cannot be easily synthesized using the method, as the tetragonal PtS phase is more stable. Here, we use a specified quartz part to locally increase the vapor pressure of sulfur in a chemical vapor deposition furnace and successfully extend this method for the synthesis of PtS2 thin films in a scalable and controllable manner. Moreover, the PtS and PtS2 phases can be interchangeably converted through a proposed strategy. Field-effect transistor characterization and photocurrent measurements suggest that PtS2 is an ambipolar semiconductor with a narrow band gap. Moreover, PtS2 also shows excellent gas-sensing performance with a detection limit of ∼0.4 ppb for NO2. Our work presents a relatively simple way of synthesizing PtS2 thin films and demonstrates their promise for high-performance ultrasensitive gas sensing, broadband optoelectronics, and nanoelectronics in a scalable manner. Furthermore, the proposed strategy is applicable for making other PtX2 compounds and TMDs which are compatible with modern silicon technologies.

Communication—A Technique for Online Continuous Manufacture of Carbon Nanotubes-Grown Carbon Fibers

Most of the methods for growing carbon nanotubes (CNTs) on the surface of carbon fibers are usually on a laboratory scale and cannot be applied to industrial production on a large scale. Here, a novel technique has been successfully developed to grow CNTs on continuous moving carbon fiber surfaces by a unique open-ended chemical vapor deposition (CVD) furnace. The experimental results show that the CNTs achieve uniform growth on the surface of carbon fibers, repairing the defects and improving the tensile strength. This study provides an original vision for the continuous growth of CNTs, and it will be a promising technique for CNTs-grown carbon fibers online manufacture.

Synthesis and thermoelectric properties of indium telluride nanowires

Thermoelectric materials, along with recent advances in nano-engineering, have attracted much attention due to the potential applications in energy conversion. A simple approach to synthesize In2Te3 nanowires was developed in a thermal chemical vapor deposition furnace by a catalyst-assisted vapor–liquid–solid growth mechanism. Structural characterization of these products was carried out using standard microscopy practices, and the thermoelectric properties of individual as-grown In2Te3 nanowires were measured using a suspended microdevice technique. This approach provides an applicable route to synthesize novel In2Te3 nanowires as well as to identify information about their thermoelectric behavior.

Powder metallurgy template growth of 3D N-doped graphene foam as binder-free cathode for high-performance lithium/sulfur battery

Here, we present a facile technique to design self-supported 3D N-doped graphene foam (NGF) via simply annealing in chemical vapor deposition furnace which used powder metallurgy nickel template and melamine as both carbon and nitrogen source. The NGF possesses highly conductive and interconnected mesoporous network. Particularly nitrogen-doping provided strong polysulfide immobilization ability, significantly suppressing the shuttle effect. The NGF was directly used as binder-free electrode which delivered a high initial discharge capacity of 987 mA h g−1 and maintains at 819 mA h g−1 after 200 cycles at 0.2 C, corresponding to 82.9% capacity retention. Specifically, even at high current density of 2 C, it still possesses a good long life cycle performance (from 633.8 mA h g−1 to 440.3 mA h g−1 after 500 cycles, with ultralow capacity fading rate of 0.061% per cycle). 7Li nuclear magnetic resonance (7Li NMR) suggested strong interaction between NGF and polysulfide. Moreover, X-ray photoelectron spectroscopy and density function theory calculation further revealed the strong interaction mostly ascribed to chemisorption and physisorption of polysulfide by pyridinic and pyrrolic nitrogen, respectively. As we know this method-based NGF as binder free electrode was first reported, which provided an effective strategy for developing high-performance Li/S batteries.

Scalable manufacturing of carbon nanotubes on continuous carbon fibers surface from chemical vapor deposition

A novel process has been successfully developed to grow carbon nanotubes (CNTs) on continuously moving carbon fibers (CF) surface by a unique open-ended chemical vapor deposition (CVD) furnace. Systematic researches were carried out under various deposition temperatures, velocities of continuous carbon fibers and catalyst concentrations. The morphologies and structures of CNTs were investigated by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM), which indicated clearly that carbon fibers with uniformly distributed CNTs were achieved, with the optimum parameters of 650 °C deposition temperature and 6 cm min−1 velocity of continuous carbon fibers and 0.05 M catalyst concentration, respectively. By means of the single fiber push-out tests, the interfacial shear strength (IFSS) of carbon fibers growing CNTs was increased significantly by 84.4% compared to the desized carbon fibers. Furthermore, the results of single fiber tensile test verified that there is scarcely any degradation in the mechanical properties of carbon fibers after the growth of CNTs with the optimum parameters. This study provides a new and original vision for scalable manufacturing of CNTs on continuous moving substrate, when compared to the traditional batch process.

Sensitive Capacitive-type Hydrogen Sensor Based on Ni Thin Film in Different Hydrogen Concentrations.

Background: Hydrogen sensors are micro/nano-structure that are used to locate hydrogen leaks. They are considered to have fast response/recovery time and long lifetime as compared to conventional gas sensors. In this paper, fabrication of sensitive capacitive-type hydrogen gas sensor based on Ni thin film has been investigated. The C-V curves of the sensor in different hydrogen concentrations have been reported.Method: Dry oxidation was done in thermal chemical vapor deposition furnace (TCVD). For oxidation time of 5 min, the oxide thickness was 15 nm and for oxidation time 10 min, it was 20 nm. The Ni thin film as a catalytic metal was deposited on the oxide film using electron gun deposition. Two MOS sensors were compared with different oxide film thickness and different hydrogen concentrations.Results: The highest response of the two MOS sensors with 15 nm and 20 nm oxide film thickness in 4% hydrogen concentration was 87.5% and 65.4% respectively. The fast response times for MOS sensors with 15 nm and 20 nm oxide film thickness in 4% hydrogen concentration was 8 s and 21 s, respectively.Conclusion: By increasing the hydrogen concentration from 1% to 4%, the response time for MOS sensor (20nm oxide thickness), was decreased from 28s to 21s. The recovery time was inversely increased from 237s to 360s. The experimental results showed that the MOS sensor based on Ni thin film had a quick response and a high sensitivity.