Simple Chemical Vapor Deposition Method Research Articles

Quadrangular ZnO:Cu nanocombs: mechanism and optical properties

Cu-doped ZnO nanocombs were fabricated on Si substrate by a simple chemical vapor deposition method. Scanning electron microscopy analyses indicate that the single nanocomb tooth has a quadrangle structure. We propose that the synthesis of the Cu-doped ZnO nanocombs includes the formation of Cu/Zn core of square-like and surface oxidation. The structural and optical properties of the ZnO:Cu nanocombs were investigated by X-ray diffraction, photoluminescence, and Raman spectra. The results show that native point defects were introduced with increasing of the Cu composition by the substitution of Cu2+ at Zn2+ lattice sites. Meanwhile, the photoluminescence show that the visible luminescence greatly enhances by the introduction of Cu and the annealing in vacuum (1 × 10−4 Pa). Magnetization measurements show that Cu-doped ZnO nanocombs exhibit room-temperature ferromagnetism (RTFM), and the ferromagnetism increases with the Cu composition. It was suggested that the origin of the enhanced RTFM in ZnO:Cu nanocombs are related to the increased intrinsic lattice defects and vacancies oxygen.

Growth and Photovoltaic Properties of High-Quality GaAs Nanowires Prepared by the Two-Source CVD Method.

Growing high-quality and low-cost GaAs nanowires (NWs) as well as fabricating high-performance NW solar cells by facile means is an important development towards the cost-effective next-generation photovoltaics. In this work, highly crystalline, dense, and long GaAs NWs are successfully synthesized using a two-source method on non-crystalline SiO2 substrates by a simple solid-source chemical vapor deposition method. The high V/III ratio and precursor concentration enabled by this two-source configuration can significantly benefit the NW growth and suppress the crystal defect formation as compared with the conventional one-source system. Since less NW crystal defects would contribute fewer electrons being trapped by the surface oxides, the p-type conductivity is then greatly enhanced as revealed by the electrical characterization of fabricated NW devices. Furthermore, the individual single NW and high-density NW parallel arrays achieved by contact printing can be effectively fabricated into Schottky barrier solar cells simply by employing asymmetric Ni-Al contacts, along with an open circuit voltage of ~0.3 V. All these results indicate the technological promise of these high-quality two-source grown GaAs NWs, especially for the realization of facile Schottky solar cells utilizing the asymmetric Ni-Al contact.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1420-y) contains supplementary material, which is available to authorized users.

Growth analysis and high-yield synthesis of aligned-stacked branched nitrogen-doped carbon nanotubes using sesame oil as a natural botanical hydrocarbon precursor

A simple spray pyrolysis-assisted chemical vapor deposition (CVD) method is employed for the growth of aligned-stack of branched nitrogen doped carbon nanotubes (bN-CNTs) using less cost effective sesame oil as natural hydrocarbon precursor. The acetonitrile (CH3CN) and ferrocene (C10H10Fe) are used for the N-doping and catalyst, respectively for the growth of nitrogen doped carbon nanotubes (N-CNTs) in aligned form. The Ar gas is passed through liquid thiophene (C4H4S) which is responsible for the branching in aligned-stacked bN-CNTs structure. The aligned-stacked bN-CNTs have been grown inside the quartz tube and no additional substrate has been used. The inner wall of quartz tubes contains black thick flake type deposition which contains aligned-stacked bN-CNT. The deposited flakes products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and Fourier transform IR spectroscopy. A suitable mechanism is elucidated for the growth of aligned-stacked bN-CNT. We have found that the initial primary growth of N-CNTs show the base growth, however secondary bN-CNTs show nearly similar diameter and follows tip growth mechanism.

Flexible Nitrogen Doped SiC Nanoarray for Ultrafast Capacitive Energy Storage.

The current trend with integrated energy-storage units in portable electronics lies in continuous advancements in nanostructured materials, thin-film manufacture technologies, and device architectures with enhanced functionality and reliability of existing components. Despite this, it is still challenging to provide cost-efficient solution to further improve the energy and power densities and cyclability of supercapacitors (SCs), especially at ultrafast rates while maintaining their environmentally friendly and even well-run at arbitrary harsh environments character. In this contribution, we report the fabrication of quasi-aligned single crystalline 3C-SiC nanowire (3C-SiCNW) array with tailored shapes and nitrogen-doping (N-doping). The resultant large-scale SiCNWs were directly grown on the surface of a flexible carbon fabric via a simple chemical vapor deposition method. We found that the SC performance of SiCNW arrays can be substantially enhanced by nitrogen doping, which could favor a more localized impurity state near the conduction band edge that greatly improves the quantum capacitance and hence increases the bulk capacitance and the high-power capability. The measured areal capacitances are higher with values of 4.8 and 4.7 mF cm(-2), in aqueous and gel electrolytes, respectively. The all-solid-state flexible textile-based SCs (TSCs) made with these electrodes are mechanically robust under bent and twisted states. Further, they show a power density of 72.3 mW cm(-2) that is higher than that of electrolytic capacitors, and an energy density of 1.2 × 10(-4) mW·h cm(-2), in association with superior rate ability, cyclability, and being environmentally friendly. Such SiCNW-TSC devices allow for operations at ultrahigh rate up to 30 V s(-1), 2 orders of magnitude higher than that of conventional supercapacitors. All these data are comparable to the reported results for 1D nanostructure-based carbon nanotubes (CNTs) or graphenes, thus showing the promising application as large-area flexible textile electronics.

Synthesis of photoactive ZnSnP2 semiconductor nanowires

Abstract

Synthesis and characterization of graphenated carbon nanotubes on IONPs using acetylene by chemical vapor deposition method

The graphenated carbon nanotubes (G-CNTs) were synthesized on monodisperse spherical iron oxide nanoparticles (IONPs) using acetylene as carbon precursor by simple chemical vapor deposition method. The reaction parameters such as temperature and flow of carbon source were optimized in order to achieve G-CNTs with excellent quality and quantity. Transmission electron microscopy (TEM) clearly illustrated that the graphene flakes are forming along the whole length on CNTs. The degree of graphitization was revealed by X-ray diffraction (XRD) analysis and Raman spectroscopic techniques. The intensity of D to G value was less than one which confirms the obtained G-CNTs have high degree of graphitization. The optimum reaction temperature for the IONPs to form metallic clusters which in turn lead to the formation of G-CNTs with high carbon deposition yield is at 900°C. The TEM shows the CNTs diameter is 50nm with foiled graphene flakes of diameter around 70nm. Our results advocate for IONPs as a promising catalytic template for quantitative and qualitative productivity of nanohybrid G-CNTs. The produced G-CNTs with high degree of graphitization might be an ideal candidate for nanoelectronic application like super capacitors and so on.

Simple Growth of Faceted Au-ZnO Hetero-nanostructures on Silicon Substrates (Nanowires and Triangular Nanoflakes): A Shape and Defect Driven Enhanced Photocatalytic Performance under Visible Light.

A simple single-step chemical vapor deposition (CVD) method has been used to grow the faceted Au-ZnO hetero-nanostructures (HNs) either with nanowires (NWs) or with triangular nanoflakes (TNFs) on crystalline silicon wafers with varying oxygen defect density in ZnO nanostructures. This work reports on the use of these nanostructures on substrates for photodegradation of rhodamine B (RhB) dyes and phenol under the visible light illumination. The photoluminescence measurements showed a substantial enhancement in the ratio of defect emission to band-edge emission for TNF (ratio ≈ 7) compared to NW structures (ratio ≤ 0.4), attributed to the presence of more oxygen defects in TNF sample. The TNF structures showed 1 order of magnitude enhancement in photocurrent density and an order of magnitude less charge-transfer resistance (R(ct)) compared to NWs resulting high-performance photocatalytic activity. The TNFs show enhanced photocatalytic performance compared to NWs. The observed rate constant for RhB degradation with TNF samples is 0.0305 min(-1), which is ≈5.3 times higher compared to NWs case with 0.0058 min(-1). A comparison has been made with bulk ZnO powders and ZnO nanostructures without Au to deduce the effect of plasmonic nanoparticles (Au) and the shape of ZnO in photocatalytic performance. The results reveal the enhanced photocatalytic capability for the triangular nanoflakes of ZnO toward RhB degradation with good reusability that can be attracted for practical applications.

Surface-Morphology-Induced Hydrophobicity of Fluorocarbon Films Grown by a Simultaneous Etching and Deposition Process

Development of facile methods to prepare hydrophobic films is of great important. We report fluorocarbon films deposited by a simple plasma-assisted chemical vapor deposition method using C3F8 and C2H2 with extra Ar and/or O2 gases. The surface characteristics of the films were examined by scanning electron microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy. The hydrophobic and oleophobic properties of the films were evaluated by measurements of static contact angle. The results showed that the film deposited with C3F8, C2H2, Ar, and O2 exhibited a water contact angle of 114°, hexadecane contact angle of 45°, and transmittance of 94.5%. Photoelectron spectra further revealed that the films contained mainly CF and CF2 bonds and thus a high F/C ratio. Introduction of O2 increased the F/C ratio, which combined with the stripe-like surface of the films achieved better hydrophobicity.

Grafting carbon nanotubes onto copper fibers using a one-step chemical vapor deposition process

A simple one-step chemical vapor deposition method of synthesizing carbon nanotubes (CNTs) on copper fiber substrates is described. This method has potential for industrial production. The specific area of the CNTs grafted onto copper fibers was significantly enlarged. A decrease in tensile strength was found after the treatment.

Zinc oxide nanostructures by chemical vapour deposition as anodes for Li-ion batteries

ZnO nanostructures are grown by a simple chemical vapour deposition method directly on a stainless steel disc current collector and successfully tested in lithium cells. The structural/morphological characterization points out the presence of well-defined polycrystalline nanostructures having different shapes and a preferential orientation along the c-axis direction. In addition, the high active surface of the ZnO nanostructures, which accounts for a large electrode/electrolyte contact area, and the complete wetting with the electrolyte solution are considered to be responsible for the good electrical transport properties and the adequate electrochemical behaviour, as confirmed by cyclic voltammetry and galvanostatic charge/discharge cycling. Indeed, despite no binder or conducting additives are used, when galvanostatically tested in lithium cells, after an initial decay, the ZnO nanostructures can provide a rather stable specific capacity approaching 70μAhcm−2 (i.e., around 400mAhg−1) after prolonged cycling at 1C, with very high Coulombic efficiency and an overall capacity retention exceeding 62%.

Synthesis and characterization of MgO nanocrystals for biosensing applications

MgO nanocrystals were prepared using a simple direct current arc plasma jet chemical vapor deposition method. Magnesium nitrate was used as source material and Mo film was used as a substrate and catalyst. The high-temperature plasma produced ensured rapid synthesis of the MgO nanocrystals. The as-prepared nanocrystals were characterized by field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, energy-dispersive spectroscopy, Fourier transform infrared spectrometry, ultraviolet–visible spectrophotometry, and photoluminescence measurements. The as-synthesized samples were found to consist of cubic MgO nanobelts and nanosheets with large surface areas and low coordination oxide ions, and contained numerous contacts, rough edges, vacancies, and doping defects. The nanostructures exhibited excellent electrochemical sensing properties with high-sensing sensitivity toward ascorbic acid. Their high electrocatalytic activity was attributed to the effect of defects and the surface electron transfer ability of the one-dimensional MgO nanobelts.

Transformation of carbon black into carbon nano-beads and nanotubes: the effect of catalysts

Structural transformation of carbon black (CB) into carbon nano-beads and nanotubes was achieved at 1000 °C using ferrocene and nickelocene as catalyst precursors using a simple and single step chemical vapor deposition method. The samples were characterized by XRD, SEM, TEM, HR-TEM and Raman spectroscopy. Results indicate that different morphological and high quality nano carbon structures were obtained using different weight ratios of catalyst to precursor. The use of bimetallic catalysts provides many different morphologies and a higher degree of crystal order of the carbon nanostructures than the use of mono-metallic catalysts. The nanotubes were mostly filled with metal nanoparticles and the degree of metal-filling is dependent on the weight ratio of catalyst precursor to CB. Metal–filled multi-walled carbon nano-bead structures with a high degree of crystalline order are also obtained at weight ratios of CB: ferrocene: nickelocene of 1:2:2.

Realization of high Curie temperature ferromagnetism in atomically thin MoS2 and WS2 nanosheets with uniform and flower-like morphology.

High Curie temperature ferromagnetism has been realized in atomically thin MoS2 and WS2 nanosheets. The ultrathin nanosheet samples were prepared via a novel, simple and efficient chemical vapor deposition method; different kinds of transition metal disulfides (MoS2 and WS2) could be obtained by sulphuring the corresponding cation sources (MoO3 and WCl6). Through related morphological and structural characterization, we confirm that large-area, uniform, few-layer MoS2 and WS2 nanosheets were successfully synthesized by this method. Both nanosheet samples exhibit distinct ferromagnetic behavior. By careful measurement and fitting of the magnetization of MoS2 and WS2 samples at different temperatures, we deconstruct the magnetization into its diamagnetic, paramagnetic and ferromagnetic contributions. The ferromagnetic contributions persist until 865 K for MoS2 and 820 K for WS2. We attribute the observed ferromagnetic properties to the defects and dislocations produced during the growth process, as well as the presence of edge spins at the edge of the nanosheets.

Electrical transport and photoresponse properties of single-crystalline p-type Cd3As2 nanowires

Cd3As2 is an important II–V group semiconductor with excellent electrical and optoelectronic properties. In this work, we report the large scale growth of single-crystalline Cd3As2 nanowires via a simple chemical vapor deposition method. Single nanowire field-effect transistors were fabricated with the as-grown Cd3As2 nanowires, which exhibited a high I on/I off of 104 with a hole mobility of 6.02 cm2V−1s−1. Photoresponse properties of the Cd3As2 nanowires were also investigated by illuminating the nanowires with white light by varying intensities. Besides, flexible photodetectors were also fabricated on flexible PET substrate, showing excellent mechanical stablility and flexible electro-optical properties under various bending states and bending cycles. Our results indicate that Cd3As2 nanowires can be the basic material of next generation electronic and optoelectronic devices.

Piezoelectric Effect of Quaic-Nanotetrapods ZnO Nanostructure

Quaic-nanotetrapods ZnO nanostructure were fabricated by a simple chemical vapour deposition method. The morphologies, crystalline qualities and optical characteristics of the quaic-nanotetrapods ZnO nanotetrapods were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) analytic technology, respectively. A piezoelectric nanogenerator based on the ZnO nanotetrapods was fabricated by a simple technique. And the energy harvesting ability is studied by experimental characterization methods and theoretical calculations.

Simple synthesis of ordered cubic mesoporous graphitic carbon nitride by chemical vapor deposition method using melamine

Ordered cubic mesoporous graphitic carbon nitride (g-C3N4) was synthesized by a simple chemical vapor deposition method using three-dimensional cubic mesoporous silica KIT-6 as the template and melamine as the precursor. X-ray diffraction, nitrogen adsorption–desorption, transmission electron microscopy and UV–vis diffuse reflectance spectra analysis techniques were used to analyze the sample. It was observed that the synthesized ordered mesoporous g-C3N4 had a cubic I4132 symmetry with a high surface area of 129.8m2/g and uniform pore size of 3.5nm. Because of these properties, the obtained ordered mesoporous g-C3N4 exhibited an enhanced photocatalytic activity for the reduction of CO2 with H2O when compared that of flake-like g-C3N4.

High performance of nanostructured ZnO film gas sensor at room temperature

Nanostructured ZnO films were synthesized by a simple chemical vapor deposition (CVD) method with different ratios of Zn:Sn in the source materials. The gas sensor using this film exhibits high gas response to ethanol and acetone at room temperature. The gas sensor also has high selectivity which the gas response to ethanol is higher than that to acetone at the same measurement conditions. In addition, visible light plays an important role for the sensitivity of the gas sensor working at room temperature. The typical emission scanning electron (SEM) images reveal that the concentration of Sn in the source materials obviously affects the morphology of the deposited films. XRD patterns of all the samples indicate that no trace of Sn, Sn alloys or Sn oxides were detected in the deposited films. Elemental analysis also shows that the film is composed of Zn and O elements, and no any Sn signals were defected. The sensing mechanism of this kind of room-temperature gas sensor is explained by free electrons random scattering model, and it was found that the nanostructured ZnO films with higher surface-to-volume ratio and higher density of defects will improve the room-temperature gas response. This study demonstrates a prospective approach to obtain high performance room-temperature ethanol gas senor.

Structural and cathodoluminescence properties of stalactite-like ZnO nanorods fabricated with assistance of Ni–Zn alloy catalyst

Stalactite-like ZnO nanorods (NRs) have been synthesized on Ni-coated Si (100) substrates using a simple chemical vapor deposition (CVD) method. The NRs are promoted by the Ni–Zn alloy catalyst particle. X-ray diffraction (XRD) result indicates that the ZnO NRs have a wurtzite structure preferentially oriented in the [0001] direction. Cathodoluminescence measurements of an individual ZnO NR exhibit three strong broad peaks (centered at 503, 515, and 526nm, respectively), which can be attributed to the oxygen vacancy related deep level emission.

Single-step synthesis of graphene-carbon nanofiber hybrid material and its synergistic magnetic behaviour

Graphene-carbon nanofiber (CNF) hybrid materials were synthesized by a simple one-step chemical vapour deposition method using propane over a Co63Ni37 alloy catalyst supported on a silicon substrate at 800°C. The process involves catalyst de-wetting, carbon diffusion and precipitation, with the additional carbon being provided by the polymer (photo-resist, HPR-504). The formation of a graphene-CNF hybrid structure was observed in the presence of the polymer. The polymer plays a crucial role in the formation of the flat carbon nanostructures. In the absence of the polymer, only carbon nanotube growth was observed with the same catalyst under identical experimental conditions. The effect of the polymeric photo-resist layer on the growth of the hybrid structure was analyzed. Structural and morphological data in combination with the Raman spectroscopic data confirmed the formation of a few layers of highly crystalline graphene and CNFs in a hybrid structure. The magnetic behaviour of these as-grown graphene-CNF hybrid samples has been analyzed by using a superconducting quantum interference device (SQUID). The results from the magnetic measurements on these samples have also been discussed.

CVD synthesis of large-area, highly crystalline MoSe2 atomic layers on diverse substrates and application to photodetectors.

Synthesis of large-area, atomically thin transition metal dichalcogenides (TMDs) on diverse substrates is of central importance for the large-scale fabrication of flexible devices and heterojunction-based devices. In this work, we successfully synthesized a large area of highly-crystalline MoSe2 atomic layers on SiO2/Si, mica and Si substrates using a simple chemical vapour deposition (CVD) method at atmospheric pressure. Atomic force microscopy (AFM) and Raman spectroscopy reveal that the as-grown ultrathin MoSe2 layers change from a single layer to a few layers. Photoluminescence (PL) spectroscopy demonstrates that while the multi-layer MoSe2 shows weak emission peaks, the monolayer has a much stronger emission peak at ∼ 1.56 eV, indicating the transition from an indirect to a direct bandgap. Transmission electron microscopy (TEM) analysis confirms the single-crystallinity of MoSe2 layers with a hexagonal structure. In addition, the photoresponse performance of photodetectors based on MoSe2 monolayer was studied for the first time. The devices exhibit a rapid response of ∼ 60 ms and a good photoresponsivity of ∼ 13 mA/W (using a 532 nm laser at an intensity of 1 mW mm(-2) and a bias of 10 V), suggesting that MoSe2 monolayer is a promising material for photodetection applications.