Thermal Chemical Vapor Deposition Method Research Articles

Evaluation of vertical alignment in carbon nanotubes: A quantitative approach

An automated quantitative study of the alignment of vertically aligned carbon nanotubes (VA-CNTs) from scanning electron microscopy (SEM) images has been demonstrated. It is based on the fact that the image gradient (directional change in intensity or color) at every pixel in the image contains the information about the anisotropy at that particular pixel i.e., the local alignment is maintained in the orthogonal direction to the gradient. Structure tensor metrics are formulated demonstrating to be able to summarize the distribution of gradient directions within the neighborhood of any pixel within a two-dimensional domain (surface). An image analysis is presented that evaluates the alignment in desired regions of interest (ROIs) in SEM images of VA-CNTs. This method has been exploited to study the alignment of two different kinds of VA-CNTs: one grown via the thermal chemical vapor deposition (T-CVD) method and the second synthesized via the plasma enhanced chemical vapor deposition (PE-CVD) method.

One-step facile growth of nitrogen-doped graphene nanowalls by catalyst-free thermal chemical vapor deposition

We report an effective technique for the growth of graphene nanowalls (GNWs) and nitrogen-doped graphene nanowalls (N-GNWs) using a thermal chemical vapor deposition (TCVD) on the catalyst-free substrate. Ethanol and mixed ethanol-imidazole were used as carbon and carbon-nitrogen sources for the growth of GNWs and N-GNWs, respectively. The effect of imidazole concentration on the morphology, nanostructure, crystal structure, crystallinity, chemical bonding and chemical structure of GNWs and N-GNWs were investigated by scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. Focused ion beam combined with TEM was utilized to analyze the growth mechanism. The results show that GNWs and N-GNWs are vertically oriented graphene nanosheets on in-plane-oriented graphitic layer/carbon nanolayer. An increase in imidazole concentration from 2.5 to 5.0 wt% increases the nitrogen content in the N-GNWs from 1.24 to 2.61 at%. The incorporated nitrogen atoms are mainly graphitic-N. One-step facile growth of N-GNWs by TCVD method without the need for a metal catalyst and plasma system was achieved.

Cooking oil waste from AYAMAS as a carbon source in forming multilayer graphene films

ABSTRACT Industrial oil waste has become a novel carbon source for graphene due to its carbon-rich and renewable nature. A new approach was proposed to produce multilayer graphene from waste industrial cooking oil (WICO) sourced from project collaborators, the AYAMAS Food Corporation Sdn Bhd. Graphene was synthesized from WICO through a double thermal chemical vapor deposition (DT-CVD) method. Nickel foil was used as a substrate to initiate the process. The amount of WICO added was varied by 10 µL increments, ranging from 10 to 50 µL. The precursor and deposition temperatures were fixed at 350°C and 1000°C, respectively. Eventually, precipitation and segregation resulted in the formation of graphene. Raman spectroscopy analysis of the graphene obtained revealed an I2D/IG ratio of less than 0.5, indicating its multilayered nature. Besides, it has 4 graphene layers by calculating the number of atomic layers. This finding was further supported by outcomes shown through Ultraviolet – visible (UV-Vis) spectroscopy, where sharp peaks of 30 µL and 40 µL were observed at 250 nm. Finally, Atomic Force Microscopy (AFM) representative images demonstrated an inverse relationship between layer numbers and surface roughness in high-WICO graphene, where a gain in layers smoothened rather than roughened its appearance. Multilayer graphene has high conductivity and a wide bandgap. These properties are applicable in electrical and thermal applications. Through a method known as DT-CVD, it was achievable to successfully produce multilayer graphene by using the usage of AYAMAS, which is usage from the frying oil industry, as a carbon source.

Restriction of residual defects of indium phosphide nanowires: Integration into single nanowire electronic device and gas sensing

Indium phosphide nanowires (InPNWs) with an average diameter size of 87 nm were successfully synthesised through thermal chemical vapour deposition (CVD) method. The InPNWs were synthesised by reacting indium metalloid and red phosphorus at 600 °C. They were synthesised possessing residual stress defects such as stacking faults. However, in this study we demonstrated how to control the generation and distribution of these defects by using indium metalloid catalyst and a modified synthesis technique. The synthesis technique was optimised to control the crystal structure, morphology, and size distribution. A single indium phosphide nanowire back-gated electronic device was fabricated using electron beam lithography. The device had resistivity of 50 Ω.cm, which confirmed that the electrical properties of indium phosphide nanowire was intact despite the presence of residual defects. The InPNWs were tested for gas sensing, and they were found to have response time of 320 s for nitric oxide gas (NO2)

Nitrogen-Doped Nickel Graphene Core Shell Synthesis: Structural, Morphological, and Chemical Composition for Planar Hybrid Solar Cells Application

In this study, nitrogen-doped nickel graphene core cells (N-NiGR) are synthesized using the thermal chemical vapor deposition method. The structural, morphological, and chemical composition properties of N-NiGR are investigated using X-ray diffractometry (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. N-NiGR has shown potential as a material that can assist charge carrier transportation in the photoactive a layer of planar hybrid solar cell (PHSC) owing to its high charge carrier mobility and stability with the solution process. Here, we investigated for the first time an enhancement of the solar cell efficiency (by up to a 2% increase) in PHSCs by incorporating the charge selective N-NiGR into the device’s photoactive layer. Synthesized N-NiGR with different concentrations are incorporated into the active layer of the devices as charge transport material. The device structure of an ITO-coated glass/Hole transport layer/(PBT7+N-NiGR+SnS)/Electron transport layer/Cathode is fabricated and the maximum power conversion efficiency of the device was observed to be about 4.35%.

Forming multilayer graphene at different precursor temperature using cooking oil waste from AYAMAS via chemical vapour deposition

Industrial cooking waste is a worldwide concern. About 24 million metric tons (Mt) of waste oil are globally generated annually from food production industries which have caused severe environmental damage to landfills. To benefit the cooking oil waste, the carbon source is used to synthesise graphene film. The carbon source is cost-effective in terms of waste reduction and environmental benefits. This study used cooking oil waste from AYAMAS Food Corporation Sdn Bhd and nickel foil as precursor and substrate, respectively. The 200 scc/m flow rate and 1000 °C of deposition temperature were fixed. Samples were prepared in different precursor temperatures in the range of 275 to 400 °C with an increment of 25 °C via the double thermal chemical vapour deposition (DT-CVD) method. Raman’s spectra showed that 350 °C had multilayer graphene with the intensity of graphene I2D/IG of 0.38, which is close to 0.5 (multilayer graphene). The UV–Vis results showed that 350 °C had the highest reflectivity value at 250 nm, while FESEM images showed a clear hexagonal shape at 350 °C. The optimum parameter for the synthesis of multilayer graphene was 350 °C precursor temperature. Multilayer graphene was successfully synthesised using industrial cooking oil waste, AYAMAS, as a carbon source via the double thermal chemical vapour deposition method.

Injection of low-energy SiCH5+ ion-beam to Si substrate during chemical vapor deposition process using methylsilane

Silicon carbide (SiC) films produced on Si substrates by the thermal chemical vapor deposition (CVD) method using methylsilane (MS) were compared with those made by the mass-selected ion-beam deposition (MSIBD) method using MS-derived 100 eV SiCH5+ ions. We also investigated the effect of SiCH5+ ion injections during the CVD process. When the substrate was 550 °C, no distinct peaks were found in the Fourier transform infrared (FTIR) spectroscopy spectra of the samples obtained by both CVD and MSIBD. By contrast, an obvious FTIR peak due to the presence of SiC was observed when SiCH5+ ions were injected to a substrate in conjunction with MS. In the case of 650 °C, we found that the film thickness was significantly increased when additional SiCH5+ ions were injected during the CVD process using MS. These results suggest that the interaction between MS and SiCH5+ has some effects on the SiC film formation at the substrate temperatures 550 and 650 °C. When the substrate temperature was set at 750 °C, the effect of the SiCH5+ ion injection on the SiC film formation was negligibly small compared to that of CVD.

3D porous graphene/double-walled carbon nanotubes/gold nanoparticles hybrid film for modifying electrochemical electrode

3D porous graphene/carbon nanotubes (Gr/CNTs) hybrid films containing nanoparticles have introduced new possibilities for the development of high-performance electrochemical sensors. Herein, we developed a novel technique for the fabrication of 3D porous graphene/double-walled carbon nanotubes/gold nanoparticles (Gr/DWCNTs/AuNPs) hybrid film on copper foils by using the thermal chemical vapor deposition (CVD) method. On these porous films, DWCNTs, Gr winkles, and a homogeneous AuNP covering were observed. These prepared 3D porous films were then transferred onto the surface of screen-printed electrodes (SPE) to investigate the electrochemical properties by using cyclic voltammetry (CV) technique. Consequently, 3D porous Gr/DWCNTs/AuNPs film modified electrodes exhibited good electrochemical characteristics with an active surface area of 2.76 times higher than that of Gr/DWCNTs film. This is due to the use of AuNPs, which improves the conductivity and surface area of the porous film.

Conversion of Carbon Dioxide into Chemical Vapor Deposited Graphene with Controllable Number of Layers via Hydrogen Plasma Pre-Treatment.

In this work, we report the conversion of carbon dioxide (CO2) gas into graphene on copper foil by using a thermal chemical vapor deposition (CVD) method assisted by hydrogen (H2) plasma pre-treatment. The synthesized graphene has been characterized by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results show the controllable number of layers (two to six layers) of high-quality graphene by adjusting H2 plasma pre-treatment powers (100–400 W). The number of layers is reduced with increasing H2 plasma pre-treatment powers due to the direct modification of metal catalyst surfaces. Bilayer graphene can be well grown with H2 plasma pre-treatment powers of 400 W while few-layer graphene has been successfully formed under H2 plasma pre-treatment powers ranging from 100 to 300 W. The formation mechanism is highlighted.

Synthesis and characterization of single‐walled carbon nanotube: Cyto‐genotoxicity in Allium cepa root tips and molecular docking studies

Herein, single-walled carbon nanotubes (SWCNTs) were synthesized by the thermal chemical vapor deposition (CVD) method, and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Raman spectroscopy, dynamic light scattering (DLS), and thermo-gravimetric analysis (TGA). The results indicated that obtained nanotubes were SWCNTs with high crystallinity and their average diameter was 10.15 ± 3nm. Allium cepa ana-telophase and comet assays on the root meristem were employed to evaluate the cytotoxic and genotoxic effects of SWCNTs by examining mitotic phases, mitotic index (MI), chromosomal aberrations (CAs), and DNA damage. A. cepa root tip cells were exposed to SWCNTs at concentrations of 12.5, 25, 50, and 100 μg/ml for 4h. Distilled water and methyl methanesulfonate (MMS, 10μg/ml) were used as the negative and positive control groups, respectively. It was observed that MIs decreased statistically significantly for all applied doses. Besides, CAs such as chromosome laggards, disturbed anaphase-telophase, stickiness and bridges and also DNA damage increased in the presence of SWCNTs in a concentration-dependent manner. In the molecular docking study, the SWCNT were found to be a strong DNA major groove binder showing an energetically very favorable binding free energy of -21.27 kcal/mol. Furthermore, the SWCNT interacted effectively with the nucleotides on both strands of DNA primarily via hydrophobic π and electrostatic interactions. As a result, cytotoxic and genotoxic effects of SWCNTs in A. cepa root meristematic cells which is a reliable system for assessment of nanoparticle toxicology were demonstrated in this study.

熱化学気相成長（CVD）法による酸化タンタルナノ粒子の合成と光触媒水分解

熱化学気相成長（CVD）法による酸化タンタルナノ粒子の合成と光触媒水分解

Growth of vertically aligned BN nanosheets via Fe-catalyzed thermal chemical vapor deposition

Hexagonal boron nitride nanosheets (BNNSs) demonstrated potential applications for ultraviolet (UV) nanoelectronics, catalytic support, electron field emission, and many other areas. However, their extensive industrial application is limited by the complicated conventional procedures for scalable preparations. In this study, vertically aligned BNNSs were directly synthesized without any substrates using Fe-catalyzed thermal chemical vapor deposition (CVD) method under a NH 3 gas flow at 1200 °C via the catalytic pyrolysis of the inorganic hybrid precursor. BNNSs grew via an Oswald ripening process assisted by oriented attachment mechanism under Fe catalyzed by analyzing the evolution process. Most nanosheets are <10 nm thick, and the number of constituent layers is typically between 10 and 20 nm. BNNSs improved crystallinity, had high UV light emission, and had excellent anti-oxidation behavior because of their unique structures. The development of a simple, high yield and environmentally friendly synthesis method for BNNSs allows for the exploration of industrial upscaling applications. • Vertically aligned BNNSs deposited by a catalytic-thermal CVD route without substrates. • The inorganic precursor was prepared by a sample wet chemical synthesis methods. • BNNSs exhibited enhanced crystallinity and UV light emission as well as remarkable oxidation resistance. • BNNSs grow via an Oswald ripening process assisted by the oriented attachment mechanism.

Low-Temperature Chemical Vapor Deposition Growth of MoS2 Nanodots and Their Raman and Photoluminescence Profiles

We report on the growth of an ordered array of MoS2 nanodots (lateral sizes in the range of ∼100–250 nm) by a thermal chemical vapor deposition (CVD) method directly onto SiO2 substrates at a relatively low substrate temperature (510–560°C). The temperature-dependent growth and evolution of MoS2 nanodots and the local environment of sulfur-induced structural defects and impurities were systematically investigated by field emission scanning electron microscopy, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) techniques. At the substrate temperature of 560°C, we observed mostly few-layer MoS2, and at 510°C, multilayer MoS2 growth, as confirmed from the Raman line shape analysis. With reduced substrate temperature, the density of MoS2 nanodots decreases, and layer thickness increases. Raman studies show characteristic Raman modes of the crystalline MoS2 layer, along with two new Raman modes centered at ∼346 and ∼361 cm−1, which are associated with MoO2 and MoO3 phases, respectively. Room temperature photoluminescence (PL) studies revealed strong visible PL from MoS2 layers, which is strongly blue-shifted from the bulk MoS2 flakes. The strong visible emission centered at ∼ 658 nm signifies a free excitonic transition in the direct gap of single-layer MoS2. Position-dependent PL profiles show excellent uniformity of the MoS2 layers for samples grown at 540 and 560°C. These results are significant for the low-temperature CVD growth of a few-layer MoS2 dots with direct bandgap photoluminescence on a flexible substrate.

Optimizing the Machining performance of CNC tools inserts coated with Diamond like Carbon Coatings under the dry cutting environment

In this research work we have coated WC (tungsten carbide) tool inserts with diamond like carbon coatings. The deposition was done using the thermal Chemical Vapour Deposition (CVD) method. We have used bagasse of sugarcane which is an agriculture waste as a carbon precursor for developing the diamond like carbon coatings. Surface finish, cutting temperature and cutting forces of as-developed diamond like carbon coatings on the WC inserts were examined and analyzed in this research work. For confirming the presence of diamond like carbon coatings on the surface of coated tungsten carbide (WC) tool inserts substrate we have used Raman spectroscopy, X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (Fe-SEM). The increase in the hardness on the developed coated samples were inspected by performing the hardness test on the coated substrates. The average evaluated Vickers Hardness number were found to be 1455.24 HV and 950.65 HV for both coated as well as un-coated samples respectively. This shows 53% rise in the hardness of the un-coated WC inserts.

Spatially Graded Millimeter Sized Mo1-xWxS2 Monolayer Alloys: Synthesis and Memory Effect.

The band gap engineering of two-dimensional (2D) transition metal dichacogenides (TMDs) could significantly broaden their applications, especially in electronics and optoelectronics. Alloying is a more effective approach to synthesize 2D ternary TMD materials with tunable bandgaps by regulating the compositions. Whether the alloying could induce memory effects is of interest as a scientific problem and worthy to be studied. A thermal evaporation-assisted chemical vapor deposition (CVD) method was proposed to grow millimeter size gradient alloyed monolayer Mo1-xWxS2. This method reveals a promising and universal methodology for the development of gradient alloyed TMDs because of the precise controlling of each precursor. The synthesized Mo1-xWxS2 monolayer crystal has a gradient composition with x ranging from 0.1 to 1. The W and Mo atoms homogeneously alloyed with random distribution in the Mo1-xWxS2 monolayer. As reported, the deep energy levels induced by sulfur vacancies can be effectively suppressed to shallow energy levels by alloying TMDs. The series distribution of the shallow energy levels in the band of the graded alloy semiconductor can act as multiple charge trapping states, which leads to obvious memory effects in the device. These results present a new opportunity for memory devices and related applications.

Designing artificial two-dimensional landscapes via atomic-layer substitution

Technology advancements in history have often been propelled by material innovations. In recent years, two-dimensional (2D) materials have attracted substantial interest as an ideal platform to construct atomic-level material architectures. In this work, we design a reaction pathway steered in a very different energy landscape, in contrast to typical thermal chemical vapor deposition method in high temperature, to enable room-temperature atomic-layer substitution (RT-ALS). First-principle calculations elucidate how the RT-ALS process is overall exothermic in energy and only has a small reaction barrier, facilitating the reaction to occur at room temperature. As a result, a variety of Janus monolayer transition metal dichalcogenides with vertical dipole could be universally realized. In particular, the RT-ALS strategy can be combined with lithography and flip-transfer to enable programmable in-plane multiheterostructures with different out-of-plane crystal symmetry and electric polarization. Various characterizations have confirmed the fidelity of the precise single atomic layer conversion. Our approach for designing an artificial 2D landscape at selective locations of a single layer of atoms can lead to unique electronic, photonic, and mechanical properties previously not found in nature. This opens a new paradigm for future material design, enabling structures and properties for unexplored territories.

Mechanism of vertically arrays of carbon nanotubes by camphor based catalysed in-situ growth

In this study, a growth mechanism of vertically aligned carbon nanotubes (VACNT) on a nanostructured porous silicon template (NPSiT) was proposed based on the experimental observations obtained. Camphor oil and ferrocene (Fe) were used as a carbon source and a catalyst, respectively. The NPSiT was optimised and used as a template to synthesise VACNT. The VACNT was synthesised on NPSiT by using a double thermal chemical vapour deposition (DTCVD) method. The synthesis was also performed via a floated method in a DTCVD reactor by using an in-situ catalyst in the absence of any catalysts pre-treatment. Each of the growth mechanisms was proposed based on the TEM images obtained at different synthesis conditions. From the results, a mixed top and bottom growth model was proposed for the growth mechanism of VACNT at the pores and pillars. On the contrary, the tip growth model was proposed for the growth inside the pores, while the valley growth model was proposed for the growth within the pillars of NPSiT. Furthermore, a mixed tip and valley growth model was proposed based on the location of Fe particles.

A UV-shielding and hydrophobic graphitic carbon nitride nanosheets/cellulose nanofibril (gCNNS/CNF) transparent coating on wood surface for weathering resistance

A UV-shielding, Hydrophobic and transparent coating was developed to improve the weathering resistance properties of wood materials while maintaining the natural aesthetic texture of the wood. Graphitic carbon nitride nanosheets (gCNNS) were used as nontoxic and metal-free UV absorber. Cellulose nanofibril (CNF) was selected as an environment-friendly and renewable film-forming carrier, which addressed the issues of agglomeration and low composite adhesion of gCNNS on the wood surface. The gCNNS/CNF composite coating was formulated on the wood surface via spin coating method. The following hydrophobic treated by thermal chemical vapor deposition (CVD) method was to solve the problem of rainwater erosion in outdoor application. After 15-day accelerated weathering tests, the total color change of the treated sample was 79.6% lower than that of the untreated one. Our newly-designed environment-friendly and weathering resistance coatings will be applied to a wide variety of substrates in the future.

Carbon nanotubes from waste cooking palm oil as adsorbent materials for the adsorption of heavy metal ions.

In this work, waste cooking palm oil (WCPO)-based carbon nanotubes (CNTs) with encapsulated iron (Fe) nanoparticles have been successfully produced via modified thermal chemical vapor deposition method. Based on several characterizations, the dense WCPO-based CNT was produced with high purity of 89% and high crystallinity proven by low ID/IG ratio (0.43). Moreover, the ferromagnetic response of CNTs showed that the average coercivity and magnetization saturation were found to be 551.5 Oe and 13.4 emu/g, respectively. These produced WCPO-based CNTs were further used as heavy metal ions adsorbent for wastewater treatment application. Some optimizations, such as the effect of different adsorbent dosage, varied initial pH solution, and various heavy metal ions, were investigated. The adsorption studies showed that the optimum adsorbent dosage was 1.8 g/L when it was applied to 100 mg/L Cu (II) solution at neutral pH (pH 7). Further measurement then showed that high Cu (II) ion removal percentage (~80%) was achieved when it was applied at very acidic solution (pH 2). Last measurement confirmed that the produced WCPO-based CNTs successfully removed different heavy metal ions in the following order: Fe (II) > Zn (II) ≈ Cu (II) with the removal percentage in the range of 99.2 to 99.9%. The adsorption isotherm for Cu (II) was better fitted by Langmuir model with a correlation coefficient of 0.82751. WCPO-based CNTs can be a potential material to be applied as adsorbent in heavy metal ion removal.

Characterization and Parametric Optimization of Performance Parameters of DLC-Coated Tungsten Carbide (WC) Tool Using TOPSIS

In this work, we have deposited the diamond-like carbon (DLC) coating on the tungsten carbide (WC) tool insert using the thermal chemical vapor deposition (CVD) method. For the growth of DLC coating, sugarcane bagasse was used as a carbon precursor. Raman spectroscopy, a field emission scanning electron microscope (FESEM), and X-ray diffraction (XRD) were used to confirm the presence of DLC coating on the tungsten carbide tool inserts. The hardness tests were also performed for inspecting the microhardness induced by the self-developed DLC coating on the tungsten carbide (WC) tool insert. To determine the optimum process parameters for the turning operation on an aluminum (6061) workpiece using a self-developed DLC-coated tungsten carbide (WC) tool insert, we have applied the technique for order preference by similarity to ideal solution (TOPSIS) methods. The process parameters considered for the optimization were feed rate, cutting speed, and depth of cut. Whereas chosen response variables were flank wear, temperature in the cutting zone, and surface roughness. TOPSIS is utilized to analyze the effects of selected input parameters on the selected output parameters. This study in this paper revealed that it was advantageous to develop the DLC coating on the tungsten carbide tool inserts for the machining applications. The results also revealed that a 0.635 mm depth of cut, feed rate of 0.2 mm/rev, and cutting speed of 480 m/min were the optimum combination of process parameters.