Chemical Vapor Deposition Technology Research Articles

Highly Efficient Osmotic Energy Harvesting in Charged Boron‐Nitride‐Nanopore Membranes

AbstractRecent studies of the high energy‐conversion efficiency of the nanofluidic platform have revealed the enormous potential for efficient exploitation of electrokinetic phenomena in nanoporous membranes for clean‐energy harvesting from salinity gradients. Here, nanofluidic reverse electrodialysis (NF‐RED) consisting of vertically aligned boron‐nitride‐nanopore (VA‐BNNP) membranes is presented, which can efficiently harness osmotic power. The power density of the VA‐BNNP reaches up to 105 W m−2, which is several orders of magnitude higher than in other nanopores with similar pore sizes, leading to 165 mW m−2 of net power density (i.e., power per membrane area). Low‐pressure chemical vapor deposition technology is employed to uniformly deposit a thin BN layer within 1D anodized alumina pores to prepare a macroscopic VA‐BNNP membrane with a high nanopore density, ≈108 pores cm−2. These membranes can resolve fundamental questions regarding the ion mobility, liquid transport, and power generation in highly charged nanopores. It is shown that the transference number in the VA‐BNNP is almost constant over the entire salt concentration range, which is different from other nanopore systems. Moreover, it is also demonstrated that the BN deposition on the nanopore channels can significantly enhance the diffusio‐osmosis velocity by two orders of magnitude at a high salinity gradient, resulting in a huge increase in power density.

In Situ Fabrication of Electrospun Carbon Nanofibers–Binary Metal Sulfides as Freestanding Electrode for Electrocatalytic Water Splitting

In search of effective and stable bifunctional electrocatalyst for electrocatalytic water splitting is still a major challenge for the highly efficient H2 production. Here, we reported a facile strategy to design high-indexed Cu3Pd13S7 nanoparticles (NPs) in situ synthesized on the three-dimensional (3D) carbon nanofibers (CNFs) by combining electrospinning and chemical vapor deposition (CVD) technology. The high-index facets with abundant active sites, the 3D architecture CNFs with high specific surface area and synergistic effect of Cu–Pd–S bonds with strong electron couplings together promote the electrocatalytic performance. The Cu3Pd13S7/CNFs shows excellent electrocatalytic activity with low overpotentials of 52 mV (10 mA cm−2) for hydrogen evolution reaction (HER) and 240 mV (10 mA cm−2) for oxygen evolution reaction (OER). The excellent protection of Cu3Pd13S7 by CNFs from aggregation and electrolyte corrosion lead to the high stability of Cu3Pd13S7/CNFs under acidic and alkaline conditions.

Epitaxial growth of semi-polar (11–22) plane AlInGaN quaternary alloys on m-plane (10-10) sapphire substrates

The semi-polar (11–22) plane AlInGaN quaternary alloys were grown successfully on the m-plane (10-10) sapphire substrates with metalorganic chemical vapor deposition technology. Optical microscope, atomic force microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction, and room temperature photoluminescence spectroscopy were used to study the effects of V/III ratio and trimethyl-indium flow rate on the characteristics of the grown semi-polar (11–22) plane AlInGaN quaternary alloys. It was found that the In composition of the semi-polar (11–22) plane AlInGaN quaternary alloys decreased as the V/III ratio increased. It was also revealed that the surface morphology, crystalline quality, and the optical property could be improved, and the phase separation in the quaternary alloy could be suppressed significantly by optimizing the V/III ratio and the trimethyl-indium flow rates.

Effect of Pyrolytic Carbon Interface Thickness on Conductivity and Tribological Properties of Copper Foam/Carbon Composite

To improve electrical conductivity of the carbon-based pantograph strip, a sliding contact material of pyrolytic carbon (PyC) coated-copper foam/carbon composite was fabricated by chemical vapor deposition technology, followed by densifying processes of furan resin impregnation and carbonization. Morphology, electrical conductivity, wear and friction behavior of the composites are investigated to clarify the effect of PyC thickness (from 0 μm to 280 μm) on tribological behaviors and current transfer characteristic. The results show that there is a good interface combination between copper foam and resin carbon matrix in the composites after the improvement of interface wettability by inserting PyC layer. The composite has great advantages in electrical conductivity and density due to the copper foam and PyC layer with three-dimensional structure. With increasing the PyC thickness, both electrical conductivity and wear resistance of the composite have steadily increasing tendency, but friction coefficient has no obvious change. In addition, an analytical model is developed to explore current transfer mechanisms of the PyC-copper foam/carbon composite, and the theoretical predictions are in agreement with the experimental observations, in term of electrical conductivity and porosity of composite preform.

The synthesis and formation mechanism of nonpolar InN nanoplates

High-crystal-quality nonpolar indium nitride (InN) nanoplates were synthesized via deploying controllable chemical vapor deposition (CVD) technology using the M-plane of GaN nanowires (NWs) as a template.

Comparative analysis and study on the rehabilitation of cruciate ligaments before and after treatment with nano-biomaterials

This paper uses porous silicon carbide as a stent, and applies chemical vapour deposition technology to prepare a new type of porous tantalum metal material and conduct preliminary biological evaluation. An experimental study on the repair of anterior and posterior cruciate ligament composite of porous tantalum metal material is carried out, and it is used in clinical practice. To treat patients with anterior cruciate ligament injury, comprehensively evaluate the biological characteristics of new porous tantalum metal and its clinical effect in the treatment of anteroposterior cruciate ligament injury, and apply a new porous tantalum rod combined with anterior cruciate ligament combined with vascular pedicle iliac flap transfer. Young and strong patients with anterior and posterior cruciate ligament injury were treated with ligament-preserving surgery. Under the condition that it was clear that bone marrow stromal cells had a bone-promoting effect, and porous tantalum metal rods could induce bone growth and biomechanical support, and vascularised iliac bone flap metastasis was studied. Young and middle-aged patients with anterior and posterior cruciate ligament injuries were treated with satisfactory results. The research results found that a new porous tantalum rod combined with anterior and posterior cruciate ligament combined with vascular pedicle iliac flap transfer effectively removed the femoral head. Internal necrosis bone promotes the new femoral head bone regeneration and provides a reliable blood supply and biomechanical support. Prevention of further collapse occurred, to assist front and rear cruciate ligament rehabilitation, and did not increase surgical complications.

Crystallization- and morphology-tunable Fe3O4@C core–shell composites decorated on carbon nanotube skeleton with tailorable electromagnetic wave absorption behavior

Herein, a scalable method is developed to fabricate carbon nanotube (CNT)/Fe3O4@C composites, in which the crystallization and morphology of the carbon shell on the surface of Fe3O4 nanoparticles can be controlled by manipulating the synthesis conditions of chemical vapor deposition technology. Owing to the synergic dissipation effect of the core–shell structure, as well as the excellent conductive loss induced by the CNT skeleton, the CNT/Fe3O4@C composite shows a minimum reflection loss of −50.1 dB at 9.7 GHz and an effective bandwidth of 4.6 GHz. This study provides new insight into preparing core–shell-structured microwave absorbers with excellent performance.

Influence of DLC Coatings Deposited by PECVD Technology on the Wear Resistance of Carbide End Mills and Surface Roughness of AlCuMg2 and 41Cr4 Workpieces

The primary purpose of this work was to study the effectiveness of using diamond-like coatings (DLC) to increase the wear resistance of carbide end mills and improve the surface quality of the processed part when milling aluminum alloy and low-carbon steel. The functional role of forming an adhesive sublayer based on (CrAlSi)N immediately before the application of the external DLC film by plasma-enhanced chemical vapor deposition (PECVD) technology in the composition of a multicomponent gas mixture containing tetramethylsilane was established in the article. The article shows the degree of influence of the adhesive sublayer on important physical, mechanical, and structural characteristics of DLCs (hardness, modulus of elasticity, index of plasticity, and others). A quantitative assessment of the effect of single-layer DLCs and double-layer (CrAlSi)N/DLCs on the wear rate of end mills during operation and the surface roughness of machined parts made of aluminum alloy AlCuMg2 and low-carbon steel 41Cr4 was performed.

Nanoplates-assembled SnS2 nanoflowers with carbon coating anchored on reduced graphene oxide for high performance Li-ion batteries

To meet people's requirements for higher performance Li-ion batteries (LIBs), many new types of anodes have been studied. Among them, the conversion reaction anode is considered to be a promising electrode based on the multi-electron reaction mechanism. As a typical conversion reaction anode, SnS2 has been widely explored for its advantages of low toxicity, easy synthesis, and high capacity. However, it usually occurs the shuttle effect of polysulfide when applied, leading to the irreversibility of the conversion reaction, and seriously hinders its application. Therefore, we firstly employed hydrothermal and low-temperature chemical vapor deposition technology to prepare a ternary composite that flower-like SnS2 anchored on reduced graphene oxide after coated carbon layer (SnS2/C-rGO). When applied in LIBs, SnS2/C-rGO displays a capacity of 952.8 mAh g−1 after cycling 90 times at 0.1 A g−1 and outstanding rate performance (479 mAh g−1 at 1 A g−1), which is significantly superior to other prepared electrodes. The high performance can be attributed to the synergistic effect of carbon layer and rGO, causing the high reversibility of conversion reaction and enhancing the cycle stability of SnS2. This investigation may provide a reference for improving the reversibility of conversion reaction anode.

Growth of GaN on monolayer hexagonal boron nitride by chemical vapor deposition for ultraviolet photodetectors

Chemical vapor deposition (CVD) technology is a simple and flexible method used to prepare high-quality crystalline materials. Traditional CVD technology, based on pre-deposited thin catalyst metal, usually produces nanostructures instead of continuous films. In this work, a continuous GaN film on a monolayer boron nitride (h-BN) insertion layer is demonstrated using CVD technology. The experimental results and theoretical calculations indicate that abundant GaN nanocrystallites are firstly formed at the edges or grain boundaries of the monolayer h-BN by quasi-van der Waals epitaxy. Then, the vapor-solid mechanism will control further growth of the GaN nanocrystallites, causing them to merge into a continuous GaN film. Meanwhile, the CVD-grown GaN ultraviolet detector exhibits a relatively high responsivity with a value of 0.57 A W−1 at 2 V. In this paper, a simple low-cost CVD method is proposed for preparing continuous films on two-dimensional materials for electronic and optoelectronic devices.

Effect of substrate surface texture on adhesion performance of diamond coating

Diamond coated tools are widely applied in the field of machining, however, its use is strictly limited by weak coating-substrate adhesion. As an effective method to generate functional surfaces, the technology of texture was applied in this research to try to change the distribution of interfacial stress and improve the adhesion of coating-substrate system. Micro-textures with different densities and shapes were prepared on the surface of cemented carbide (YG6) by ultraviolet nanosecond laser, and heteroepitaxial growth of diamond coating on textured surface was realized by hot filament chemical vapor deposition (HFCVD) technology. By means of Rockwell indentation tests, micro-Raman spectrometer and thermo-solid coupling simulation analysis, the effect of textures on the adhesion of diamond coating was studied. Results indicate that the adhesion of coating-substrate increases with the increase of the micro-textures density. The normal compressive stress of diamond coating at the edges of texture inhibits the propagation of interfacial cracks, resulting in the deviation of the crack propagation path.

Preparation and improved photoelectrochemical properties of InGaN/GaN photoanode with mesoporous GaN Distributed Bragg reflectors

We fabricate the large-area and highly reflective mesoporous GaN (MP-GaN) Distributed Bragg reflectors (DBRs) via an electrochemical etching technology in HNO3 solution for the first time and then use the DBRs as the template in growth of InGaN/GaN structure by the metal organic chemical vapor deposition (MOCVD) technology. The InGaN/GaN structure with MP-GaN DBRs acts as the photoanode during photoelectrochemical (PEC) water splitting experiments in 1 M HBr solution for the first time. Compared to the sample without MP-GaN DBRs, the InGaN/GaN structure with the MP-GaN DBRs presents significantly increased photoluminescence (PL) intensity, which is attributed to light reflection effect of the bottom MP-GaN DBRs and improved internal quantum efficiency (IQE) of the multiple quantum wells (MQWs) layer. More interestingly, the InGaN/GaN structure with the MP-GaN DBRs presents markedly improved PEC properties such as a low onset voltage (−0.61 V vs. RHE), a 4.5-fold enhancement in photoconversion efficiency and good stability.

Yb/Er coordinatively doping in bilayer WSe2 for fascinating up-conversion luminescence

Abstract Benefited from the controllable synthesis of large-scale transition metal dichalcogenides (TMDCs), abundant physical properties of TMDC van der waals heterostructures, such as moire-exciton, electrostatic gating effects, interlayer magnetism, are widely reported. In optoelectronic categories, the applications of TMDC van der waals heterostructures involve interlayer exciton lasers, single photon emitters, and light-emitting diodes (LEDs). However, the employment of TMDCs in visible light emitter is still challenging due to their narrow band gap. The up-converted luminescence from TMDCs could be an effective way to achieve this goal, which has been reported rarely. In this work, the rare earth Yb/Er co-doped bilayer WSe2 of atomic thickness is designed and synthesized using precursor ultrasonic mixing and molten-salt assisted chemical vapor deposition technology. A fascinating up-converted luminescence has been realized on the Yb–Er co-doped bilayer WSe2 excited by 980 nm laser. The up-conversion luminescence peak at 550 nm originates from Er3+ energy level transition 4S3/2→4I15/2. Furthermore, a modulated visible electroluminescence is probed from the LED with architecture of Cr/Au electrodes on Yb–Er co-doped bilayer WSe2/monolayer MoSe2 van der waals heterostructure. Unveiling up-conversion luminescence in TMDCs opens a novel way of utility in photomedicine, infrared thermometer, and infrared photography, etc.

Higher Operating Temperature IR Detectors of the MOCVD Grown HgCdTe Heterostructures

This paper summarizes progress in metal organic chemical vapour deposition (MOCVD) technology achieved in recent years at the Institute of Applied Physics, Military University of Technology and VIGO System S.A. MOCVD with a wide range of composition and donor/acceptor doping and without post-growth annealing is a very convenient tool for the deposition of HgCdTe epilayers used for uncooled infrared detectors. Particular attention is focused on: surface morphology improvement, doping issues, diffusion processes during growth study, substrate issues, crystallographic orientation selection. In this respect, MOCVD technology improvement influencing IR detector parameters is shown. CdTe buffer layer deposition allows HgCdTe heterostructure growth on GaAs substrates. Theoretical modelling using APSYS platform supports designing and better understanding of the carrier transport mechanism in detector’s structures. Secondary ion mass spectrometry profiles allows to compare projected and obtained structures and revealed diffusion processes of the elements. A wide range of different types of infrared detectors operating at high operating temperature conditions has been constructed: photoresistors, non-equilibrium photodiodes, dual-band photodiodes, barrier and multiple detectors. The methodical research efforts contributed to the time constant reduction are important in many detector applications. Future challenges and prospects are also discussed.

Microstructure of boron doped diamond electrodes and studies on its basic electrochemical characteristics and applicability of dye degradation

The microstructure of boron doped diamond (BDD) is the main factor affecting its degradation performance, and the type of wastewater is also a major factor. In this paper, niobium based BDD electrodes were prepared by hot filament chemical vapor deposition (HFCVD) technology at 650 °C, 750 °C, 850 °C substrate temperatures. For the three BDD electrodes with different substrate temperatures, the comparison of electrochemical performance and degradation efficiency was conducted. The results showed that with the increase of deposition temperature, the microstructure of BDD electrodes surface changed, the grain size and boron content increased, and the sp3/sp2 phase ratio also increased, which caused the electrochemical oxidation performance of the BDD electrodes improved, the color removal rate of the electrodes increased, and the energy consumption reduced. The decolorization rates of the 850 °C-BDD electrode for Reactive orange X-GN and Reactive blue 19 at 180 min were 99.79 % and 93.38 %, respectively. In addition, the degradation performance of 8 dyes by 850 °C-BDD electrode was systematically studied. Affected by the molecular structure of dye, the degradation degree of each type of dye from easy to difficult was: Fuchsin acid, Reactive red 2, Acid orange G, Alizarin red, Acid blue 92, Reactive orange X-GN, Orange II, Reactive blue 19.

Novel Low-Temperature Chemical Vapor Deposition of Hydrothermal Delignified Wood for Hydrophobic Property.

As a hydrophilic material, wood is difficult to utilize for external applications due to the variable weather conditions. In this study, an efficient, facile, and low-cost method was developed to enhance the hydrophobicity of wood. By applying the low-temperature chemical vapor deposition (CVD) technology, the polydimethylsiloxane-coated wood (PDMS@wood) with hydrophobic surface was fabricated employing dichlorodimethylsilane as the CVD chemical resource. The result of water contact angle (i.e., 157.3°) revealed the hydrophobic behavior of the PDMS@wood. The microstructures of the wood samples were observed by scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) analysis verified PDMS successfully coated on wood surfaces. The chemical functional groups of the PDMS@wood were investigated by Fourier transform infrared (FT-IR) and Raman spectra. The thermogravimetric results indicated the enhanced thermal stability of the wood after PDMS coating. In addition, the stability test of PDMS@wood indicated that the hydrophobicity properties of the PDMS@wood samples were preserved after long-time storage (e.g., 30 days). The scratch test was carried out to examine the abrasion resistance of the hydrophobic coatings on PDMS@wood surface. It was suggested that low-temperature CVD process could be a successful approach for fabricating hydrophobic wood.

Multi-layer hybrid coatings with high gas barrier properties and optical quality

The combustion chemical vapour deposition (CCVD) technology was used to generate thin inorganic silica-coatings on polyethylene terephthalate (PET) films. These SiOx base layers were combined with flexibly configurable hybrid sol-gel layers to create multi-layer systems with improved property profiles, such as high gas barrier against oxygen or water vapour.The inorganic-organic sol-gel hybrid layer is produced by the simultaneous step growth polymerization of three reactants: 3-aminopropyltriethoxysilane, 4,4′-methylene-bis(N,N-diglycidylaniline) and aluminium-tri-sec-butoxide. The controlled sol-gel process allows simultaneous covalent bond formation between the silica, alumina and epoxy resin containing components, which is crucial for the target property of the hybrid material layer.The so synthesized ternary hybrid material layer has a significantly improved gas barrier effect as well as a higher light transmittance compared to the unmodified coating. For the reduction of the Oxygen Transmission Rate (OTR), the exact adjustment of the Al component proved to be the main influencing factor.The combination of CCVD and sol-gel technology is very well suited to create composite systems whose gas barrier properties are sufficient for use in the food and pharmaceutical packaging sector, even for sensitive content. These coatings have very low values for the OTR which range up to 10−1 cm3 / (m2 d bar) as well as adequate transmission rates for water vapour which range up to 100 g / (m2 d). In addition, these composite layers can also ensure light transmission. By applying a coating system based on three single layers, the initial transmittance of the PET film could be exceeded by 1% up to 87%. Thus, composite layers even with a total thickness of about 400 nm, which were completely generated under ambient conditions, can build up a barrier effect on PET films.

Effects of Ⅴ/Ⅲ ratio and Cp2Mg flow rate on characteristics of non-polar a-plane Mg-delta-doped p-AlGaN epi-layer

Abstract The non-polar a-plane Mg-delta-doped p-AlGaN epi-layers with excellent electrical conduction were achieved on r-plane sapphire substrates via metal organic chemical vapor deposition technology. The impacts of Ⅴ/Ⅲ ratio and Cp2Mg flow rate on the properties of the non-polar p-AlGaN epi-layers were investigated with scanning electron microscopy, high-resolution X-ray diffraction, Raman spectroscopy, and Hall effect measurement. It was discovered that the crystalline quality and the electrical conductivity were extremely relied upon the Ⅴ/Ⅲ ratio and Mg-doping level. Actually, a hole concentration of 3.7 × 1017 cm−3 and an electrical resistivity of 2.6 Ω ⋅ cm were obtained for non-polar p-Al0.12Ga0.88N epi-layer by carefully optimizing the Ⅴ/Ⅲ ratio and Cp2Mg flow rate during the epitaxial procedure. In addition, the results revealed that improvement on electrical conductivity was ascribed to the evident repression of self-compensation effect generated by decreasing in the densities of the nitrogen vacancy (VN) as well as the VN-related complexes and the Mg-related defects via the employment of the proper Ⅴ/Ⅲ ratio and the Mg-doping concentration.

Improvement in structural and electrical characteristics of nonpolar a-plane Si-doped n-AlGaN

Nonpolar Si-doped AlGaN with high electron concentration (EC) and superior surface morphology (SM) layers were successfully grown on r-plane sapphire substrates for the first time with metal organic chemical vapor deposition technology. X-ray diffraction, cross-sectional scanning electron microscope, ultraviolet–visible absorption spectroscopy, atomic force microscopy, and Hall measurements were used to examine the influence of indium surfactant and an extra AlGaN buffer on crystalline quality (CQ), SM, and electrical characteristics of the nonpolar Si-doped n-AlGaN, respectively. The characterization results revealed that the anisotropy in CQ of the nonpolar Si-doped n-AlGaN epi-layers was suppressed effectively, and the SM, as well as the electrical properties including EC, electron mobility (EM), and electron resistivity (ER), had been significantly improved by using indium surfactant and an extra AlGaN buffer layer. In fact, an EC as high as 4.8 × 1017 cm−3, an EM up to 3.42 cm2/V s, an ER down to 4.78 $$\Omega \bullet $$cm , and a root-mean-square value as small as 8.2 nm for surface roughness was achieved for the nonpolar Si-doped n-AlGaN with a relatively high Al composition of 50%.

On the Impact of Electron Leakage on the Efficiency Droop for AlGaN Based Deep Ultraviolet Light Emitting Diodes

In this work, we have investigated the origin of efficiency droop for AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). We find that the efficiency droop is likely to be caused by the electron leakage for DUV LEDs studied in this work. The electron leakage arises from the unbalanced electron and hole injection efficiencies. The correlation between the efficiency droop and the electron leakage can be numerically calculated by manipulating the conduction band barrier height of the p-AlGaN electron blocking layer (p-EBL) for the proposed DUV LEDs. For the purpose of demonstrating that the efficiency droop for DUV LEDs can be experimentally decreased by reducing the electron leakage, a p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -GaN/In0.15Ga0.85N/n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -GaN tunnel junction on DUV LED is grown by using metal organic chemical vapor deposition (MOCVD) technology. The tunnel junction helps to enhance the hole injection, thus decreasing the electron leakage and the efficiency droop. Moreover, the parasitic emission in the p-type hole injection layer is no longer observed thanks to the decreased electron leakage level.