Assisted Chemical Vapor Deposition Technique Research Articles

One-step synthesis of cobalt nanosheets depositing with carbon microsphere by microwave plasma assisted reduction chemical vapor deposition technique against electromagnetic pollution

The rational design of magnetic carbon composites in both composition and microstructure has significant potential for acquiring excellent electromagnetic wave absorbing materials (EAMs). In this study, Co@carbon magnetic composites were prepared by employing a novel microwave plasma assisted reduction chemical vapor deposition (MPARCVD) technique, which was highly efficient, low-cost, and energy-saving. The depositing of graphitized carbon microspheres on the surface of Co nanosheets could enrich the available loss mechanisms. Furthermore, the lamelliform morphology with a large aspect ratio of the composites was beneficial to subtly improve the dielectric properties under a low filler content. As a consequence, the minimum RL reached up to −65.7 dB and the radar cross-sectional area reduction attained to 22.3 dBm 2 with only 20 wt% loading content. The MARCVD technology opened a novel strategy and avenue for acquiring magnetic carbon composites as candidates for lightweight and high-performance EAMs.

Multi-layer growth of tungsten disulphide using thermal chemical vapour deposition

Transition metal dichalcogenides, in their 2D form are proven to be significant material for next-generation nanoelectronic and optoelectronic devices. However, for the realization of practical applications, it is very important to devise facile, and cost-effective synthesis routes without compromising their quality. In this work, multi-layer 2D tungsten disulphide (WS2) has been synthesized using thermal assisted chemical vapour deposition technique. The synthesis was carried out using two different substrates, and the effect of relative position of tungsten trioxide powder and substrate on the multi-layer growth of WS2 has been studied. The nucleation density and layer number is observed to be varying with the reaction time and the type of the substrate. The as-synthesized samples were characterized by using field emission scanning electron microscopy, and Raman spectroscopy.

Impedance Spectroscopic Study of Nickel Sulfide Nanostructures Deposited by Aerosol Assisted Chemical Vapor Deposition Technique.

This research aims to synthesize the Bis(di-isobutyldithiophosphinato) nickel (II) complex [Ni(iBu2PS2)] to be employed as a substrate for the deposition of nickel sulfide nanostructures, and to investigate its dielectric and impedance characteristics for applications in the electronic industry. Various analytical tools including elemental analysis, mass spectrometry, IR, and TGA were also used to further confirm the successful synthesis of the precursor. NiS nanostructures were grown on the glass substrates by employing an aerosol assisted chemical vapor deposition (AACVD) technique via successful decomposition of the synthesized complex under variable temperature conditions. XRD, SEM, TEM, and EDX methods were well applied to examine resultant nanostructures. Dielectric studies of NiS were carried out at room temperature within the 100 Hz to 5 MHz frequency range. Maxwell-Wagner model gave a complete explanation of the variation of dielectric properties along with frequency. The reason behind high dielectric constant values at low frequency was further endorsed by Koops phenomenological model. The efficient translational hopping and futile reorientation vibration caused the overdue exceptional drift of ac conductivity (σac) along with the rise in frequency. Two relaxation processes caused by grains and grain boundaries were identified from the fitting of a complex impedance plot with an equivalent circuit model (Rg Cg) (Rgb Qgb Cgb). Asymmetry and depression in the semicircle having center present lower than the impedance real axis gave solid justification of dielectric behavior that is non-Debye in nature.

Myeloperoxidase-induced degradation of N-doped carbon nanotubes: Revealing possible atomistic mechanisms underlying hypochlorite-driven damage of nanotube walls

We present a combined experimental and theoretical study dedicated to analyze the human myeloperoxidase (h-MPO)-catalyzed degradation of oxidized nitrogen-doped multi-walled carbon nanotubes (NMWCNTs-Ox) in vitro at 27 °C. NMWCNTs are synthesized by the aerosol assisted chemical vapor deposition (AACVD) technique and are characterized by employing transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), as well as Raman and X-ray photoelectron spectroscopies. H-MPO degradation, involving hypochlorous acid and hypochlorite species, leads to complete removal of CNTs with diameters smaller than 75 nm from the samples. Simultaneously, for larger sizes, it produces the formation of highly deformed NMWCNTs decorated with NaCl nanoparticles, which exhibit reduced cytotoxicity in exposed monocytes studies compared with the initial nanotube samples. Density functional theory (DFT) calculations performed on model nitrogen-doped CNTs are also presented to explore, at an atomistic level, the fundamental aspects underlying degradation. Our DFT results reveal that reactivity of carbon walls is significantly affected around N-doped pyridinic, pyrrolic, and substitutional sites, leading to the existence of HClO molecules physisorbed close to those defects and high local concentrations of chemisorbed ClO species on C atoms adjacent to the N-rich regions. The formation of these hypochlorite molecular islands on the nanotube surface facilitates ClO dissociation producing strongly bound O species and Cl atoms that can be carbon bonded or released into the environment. The previous surface reaction results in the cleavage of the underlying C–C bonds, creating holey regions on the graphitic walls. The continuation of this process would lead to the formation of larger holes on the nanotube surface, allowing, on the one hand, the permeation of ClO molecules to the internal layers and, on the other hand, producing a reduction of the NMWCNTs diameter as observed from our experimental data.

Surface modification of Co-Cr-Mo alloy by plasma assisted CVD

Co-Cr-Mo alloy is a key material of total joint replacements. Ions releases (corrosion) in addition to Wear are a common failure mechanism in metal-on-metal (MOM). One of many new methods to coating DLCs is Plasma assisted chemical vapor deposition (PACVD) technique. Using PACVD to coat Co-Cr-Mo alloy is a new technique needs many research to allow for using in biomedical applications. DLCs provides smooth morphology surface. That morphology is reducing of surface roughness improvement tribological behavior. Using a best condition of coating parameters are Acetylene gas flow rate 40 sccm and voltage is 1600 v with Voltage between electrodes is 250 v for (PACVD) results coating film with 83% diamond like carbon (sp3) with thickness is 100 μm. Observations of surface indicate by suing both SEM and AFM indicate no crack and smooth surface with surface roughness is 0.679 µm in DLCs. Raman tested to determine the amount diamond like carbon (sp3) is 83%.that meaning the minimum of hydrogen content. Hardness tested to indicate increasing up to three times. The hardness of coating samples is 11.77 Hv, while in substate was about 3.923 Hv. Corrosion test by using simulated body fluid solution. DLCs improved the corrosion resistance of Co-Cr-Mo alloy with semi-body fluid solution. The samples have spontaneously passive in semi-body fluid solution at current density is 32.6 × 10−6 A/cm2 at potential is −416.5 mV for uncoated sample. While for DLCs current density is 3.92 × 10−6 A/cm2 with the potential of −35.5 mV. From comparing the maximum current for both samples shows the density for uncoated more than the DLCs, it is 207 and 11.1 mA/cm2 respectively. This reduction of the current densities explains improvement of corrosion resistance due to the surface modification by DLCs. Also, the reduced of electron conductivity of DLCs in comparison to uncoated sample indicate low electrical conductivity of the DLCs. That reduces the electron transport and the exchange of electrical charges at the samples surface, which is necessary for the electrochemical corrosion. In addition, reduces the Ni ion release of alloy.

Fabrication of Ag-ZnO composite thin films for plasmonic enhanced water splitting

Research on plasmonic photoactive materials has resulted in some significant advancements in UV–Vis photo-active catalytic reactions. In this study, pristine ZnO and Ag-ZnO thin films were deposited onto fluorine doped tin oxide (FTO) coated glass substrate from a newly synthesized zinc molecular precursor, {Zn5(TFA)7(OH)2(H2O)4(OAc)}n.2(C4H6O2) [TFA = trifluoroacetate, OAc = acetate], and its homogenous solution with Ag(CH3COO), respectively, via the aerosol assisted chemical vapor deposition (AACVD) technique. The precursor was analyzed by microanalysis, melting point, proton nuclear magnetic resonance (1H NMR), Fourier transformed infra-red (FT-IR), thermogravimetry (TG) and single crystal analysis. Powder X-ray diffraction (PXRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray (EDX), UV–Vis spectroscopic and photoluminescence (PL) analyses were carried out to investigate the phase purity, structural morphology, composition and optical properties of the as-synthesized thin films. Linear scan voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) confirmed that the photo-electrochemical performance of Ag-ZnO for water splitting was much improved compared to ZnO. These results confirm that Ag is an efficient surface plasmon resonance photosensitizer which mediates the interfacial charge transfer process, thus extending the light response of pristine ZnO into the visible region.

Reduced holey graphene oxide film and carbon nanotubes sandwich structure as a binder-free electrode material for supercapcitor

A novel carbon nanotubes (CNTs) and reduced holey graphene oxide film (RHGOF) sandwich structure has been fabricated to enhance its electrochemical properties. CNTs are grown by a catalyst assisted chemical vapor deposition technique, interpenetrated between the RHGOF layers. A RHGOF/CNTs hybrid film is used as a binder-free supercapacitor electrode. The grown CNTs in the graphene layers structure act as spacers and bridges to increase the counductivity of RHGOF, while the grown CNTs on the surfaces of the graphene contribute to increase the specific surface area of RHGOF. The results demonstrate that the synthesized porous, flexible and binder free hybrid electrode has advantages of higher ion diffusion rate, longer diffusion length and larger ion accessible surface area as compared to the pristine graphene which results in an extra ordinary galvanostatic charge-discharge specific capacitance of 557 F/g at a current density of 0.5 A/g, with excellent rate capabilities and superior cyclic stabilities.

Statistical study of the variable speed of an AACVD device implemented in the UTP

The spray assisted chemical vapor deposition (AACVD) technique is used to make thin film growth through the spraying of a precursor solution in the form of droplets, by means of a nozzle moving horizontally along the substrate. One of the most influential variables in the growth of the films is the speed with which the nozzle moves, since the deposition uniformity depends on this, which is directly related to the different physical properties of the coating. This paper briefly shows the electronic control built for the manipulation of this variable and a statistical study is presented that allowed to determine that the experimental speed presents oscillations less than 10% with respect to the programmed value. In addition, comparative transmittance spectra are shown where the reproducibility and repeatability of the coatings manufactured with the AACVD equipment built in the UTP is observed.

An evaluation of the effects of the N2/Ar gas flux ratio on various characteristics of TiC0.3N0.7 nano-structure coatings on the cold work tool steel by pulsed DC-PACVD

As the radius of argon ions is larger than other fragments in the medium of plasma in the plasma assisted chemical vapor deposition (PACVD) technique, it affects the microstructure and mechanical properties of the coatings. Thus, in this paper, the influence of various N2/Ar gas flow ratios on characteristics of TiCN thin coatings on a cold work tool steel have been investigated. These coatings were produced by the method of pulsed DC-PACVD at a temperature of 480 °C. Field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) were employed for determining the microstructure and chemical composition of various coatings. Various mechanical properties such as micro-hardness, nano-hardness, wear behavior, and toughness were also investigated. The obtained results indicated that the N2/Ar gas flow ratio of 0.6 led to optimal mechanical properties. Such ratio reduced the value of the friction coefficient to 0.15 owing to lower roughness. Besides, the growth rate was found to be highest corresponding to a gas flow ratio of 0.5. It was found that the titanium content in such coatings could enhance the growth rate of TiCN coatings. XRD results also demonstrated that the N2/Ar gas flow ratio value of 0.4 resulted in the formation of the TiN and TiC plus the free carbon phases instead of forming the TiC0.3N0.7 phase. The N2/Ar gas flow ratio value of 0.7 also lowered mechanical properties such as the toughness and the micro-hardness. Their values were found to be 2.3 MPam0.5 and 940 HV0.01, respectively.

Bis(2-hydroxy-1-naphthaldehydato)zinc(II) as a precursor for the preparation of ZnO thin films through aerosol-assisted chemical vapour deposition

Bis(2-hydroxy-1-naphthaldehydato)zinc(II) complex was used as a precursor to deposit ZnO films on glass substrates at 350, 400, and 450 °C using aerosol assisted chemical vapour deposition (AACVD) technique. The optical properties of the films were investigated by UV–vis spectroscopy and photoluminescence (PL). The results show that temperature of decomposition has a huge effect on the material deposited. The optical characterization of ZnO thin films deposited on the glass substrate reveal the direct optical band gap in the range of 3.15 to 3.08 eV. The photoluminescence spectra were red shifted as the decomposition temperature was increased. The diffraction patterns of all ZnO thin films prepared at different temperatures show the face centred cubic structures with the lattice parameter of a = b = c = 4.289 A°. The structural properties of the ZnO thin films show an improvement in crystallinity of the materials when the temperature was increased.

Differences in hydrogen absorption over Pd and Pt functionalized CVD-grown GaN nanowires

In this study, we report the differences in hydrogen (H2) absorption properties of platinum (Pt) and palladium (Pd) functionalized gallium nitride (GaN) nanowires via gas sensing studies. GaN nanowires of ∼25−200 nm diameter and ∼50−75 μm length are grown uniformly over large area (10×10 mm2) using Au assisted chemical vapour deposition technique. The nanowires are grown at 900 for 2 h using gallium (Ga) as source material and ammonia (NH3) as the reacting gas. The nanowires are functionalized with Pd and Pt nanoclusters using solution technique. H2 absorption by these functionalized nanowires which is manifested as gas sensing response is compared in the temperature range of 50–200. The role of surface kinetics in Pd and Pt is shown to be responsible for the difference in the sensor response.

Influence of compactness and formation of metallic secondary phase on the thermoelectric properties of Cu2ZnSnS4 thin films

Thermoelectric studies of Cu2ZnSnS4 (CZTS) thin films deposited at different substrate temperatures by ultrasonic assisted chemical vapor deposition technique have been carried out. In order to identify the effect of compactness, crystallinity and formation of secondary phases (Cu2−xS and SnS2) on the thermoelectric properties of CZTS thin films, the films were deposited at different substrate temperatures. Detailed analysis of temperature dependent electrical resistivity (ρ) and Seebeck coefficient (S) have been carried out. Significant enhancement in the value of thermoelectric power factor (S2/ρ) is achieved in CZTS film deposited at 375°C substrate temperature, which is correlated to the compactness of thin films, improved crystallinity and presence of metallic secondary phase. Furthermore, Surface topography and surface potential studies also carried out to study the roughness and distribution of interfaces between CZTS and secondary phases (Cu2−xS and SnS2) in CZTS thin films.

Synthesis, crystal structure and vapour pressure studies of novel nickel complex as precursor for NiO coating by metalorganic chemical vapour deposition technique

A square planar nickel complex namely bis(N-propyl-3-methylsalicylaldimine)nickel(II) (2) was prepared from its parent compound bis(3-methylsalicylaldehydato)nickel(II) (1) by adding n-propylamine in a methanol medium. The TG/DTA analysis of the resultant Schiff's base complex 2 in the solid phase was evaluated in an inert N2 environment at atmospheric pressure. Complex 2 was completely volatile giving nil residue at 335 °C in a single weight loss step, whereas the complex 1 was found to be non-volatile giving 47% residues till 455 °C. The change in volatility of 2 was brought about by the condensation of n-propylamine with 1 which replaced aldehyde O (-CH=O) with N (-CH=N). The volatile precursor 2 was characterised by single crystal XRD, 1H and 13C NMR, FT-IR, C, H and N elemental analysis and mass spectrometry. The temperature dependence of the saturated vapour pressure and enthalpy of vapourisation (ΔvapH° = 97.9 ± 2.0 kJ mol−1) of the volatile complex 2 was determined by a transpiration TG technique in the temperature range 499–562 K. Subsequently, it was used as a precursor for the deposition of nickel oxide (NiO) thin film on Si(100) substrate by employing plasma assisted metal-organic chemical vapour deposition (PAMOCVD) technique. The nano-crystalline nickel oxide thin films were analysed by XRD and SEM/EDX. X-ray photoelectron spectroscopy (XPS) study confirmed the formation of stoichiometric NiO phase. The band gap of the NiO thin film was found to be 4.31eV exhibiting a blue shift as observed from DRS-UV.

Ultrasonic Assisted Mist Chemical Vapor Deposition Deposited MgO for AlGaNGaN Metal-Insulator-Semiconductor Ultraviolet Photodetector

This work uses an ultrasonic assisted mist chemical vapor deposition (UAM-CVD) technique to deposit the MgO film of 10nm as the insulator layer of the AlGaNGaN metal-insulator-semiconductor (MIS) ultraviolet photodetector. The illumination area was designed to be 0.47 mm2. The thickness of the MgO film is confirmed by transmission electron microscopy (TEM). The optical characteristics of the MgO film like refractive index, extinction coefficient, and optical transmittance are characterized by the ellipsometer and the UVVISIR spectrometer. The dark current of the MIS photodetector is 5.03pA, which is much lower than the Schottky barrier photodetector of 4.23nA. The MIS photodetector shows higher internal photoconductive gain compared to the Schottky barrier photodetector. Therefore, the MIS photodetector has high photoresponsivity of 0.44AW (360nm). Such high responsivity gives the MIS photodetector a low noise equivalent power of 3.83 1012 W (360 nm) and high detectivity of $1.79\times 10^{10}$ Jones (360 nm).

MgTi2O5 thin films from single molecular precursor for photoelectrochemical water splitting

Magnesium dititanate MgTi2O5, thin films have been grown on fluorine doped tin oxide (FTO) substrates using a newly synthesized heterobimetallic single molecular precursor [Mg2Ti4(O)2(OH)4(TFA)8(THF)6]·THF (1) (where TFA=trifluroacetato and THF=tetrahydrofuran) using the aerosol assisted chemical vapor deposition technique (AACVD). The precursor complex (1), isolated in crystalline form by reacting magnesium (II) acetate tertahydrate with titanium (IV) isopropoxide and trifluroacetic acid in THF solution, was characterized by FTIR, single-crystal X-ray diffraction and thermogravimetric analyses. Thin films prepared at 500, 550 and 600°C were inspected by X-ray diffraction (XRD), field emission gun-scanning electron microscopic (FESEM), and energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), which demonstrated the development of phase pure orthorhombic porous microspherical objects of MgTi2O5 with precise stoichiometry. The optical analysis showed that MgTi2O5 has a direct band gap of 3.4eV. The photoelectrochemical (PEC) experiments on MgTi2O5 electrodes showed maximum anodic photocurrent density of 400μA/cm2 at 0.7V vs. Ag/AgCl/3M KCl under simulated solar irradiation of AM 1.5G (100mW/cm2) in 1M NaOH. The improved PEC performance of MgTi2O5 electrode was attributed to the increased photo absorption ability, elevated surface area, and more efficient electron/hole transfer which were confirmed by measurements such as linear sweep voltage, transient photocurrent and electrochemical impedance spectroscopy.

Tailoring the optical bandgap and magnetization of cobalt ferrite thin films through controlled zinc doping

In this report, the tuning of the optical bandgap and saturation magnetization of cobalt ferrite (CFO) thin films through low doping of zinc (Zn) has been demonstrated. The Zn doped CFO thin films with doping concentrations (0 to 10%) have been synthesized by ultrasonic assisted chemical vapour deposition technique. The optical bandgap varies from 1.48 to 1.88 eV and saturation magnetization varies from 142 to 221 emu/cc with the increase in the doping concentration and this change in the optical and magnetic properties is attributed to the change in the relative population of the Co2+ at the tetrahedral and octahedral sites. Raman study confirms the decrease in the population of Co2+ at tetrahedral sites with controlled Zn doping in CFO thin films. A quantitative analysis has been presented to explain the observed variation in the optical bandgap and saturation magnetization.

A Review on Titanium Nitride and Titanium Carbide Single and Multilayer Coatings Deposited by Plasma Assisted Chemical Vapor Deposition

In this paper, we reviewed researches about the titanium nitride (TiN) and titanium carbide (TiC) single and multilayer coatings. These coatings were deposited by the plasma assisted chemical vapor deposition (PACVD) technique. Plasma-based technologies are used for the processing of thin films and coatings for different applications such as automobile and aerospace parts, computer disc drives, food industry and surgical/medical instruments. We describe the state of the performance of different coating systems and thin film architectures in PACVD suitable for industrial-scale or laboratory applications. Mechanical properties of coatings such as wear resistance, hardness and the scratch resistance, structural characteristics, physical and chemical properties like coatings adhesion into different substrates, wetting behavior and corrosion resistance were studied. Thus, this paper represents a source of information for those who want to familiarize with the status of knowledge in the area of materials science of functional coatings, in particular TiN/TiC coatings that was deposited by a new Plasma-based technologies.

Magnetically tunable bandpass filter using cobalt ferrite thin film

Abstract Cobalt ferrite thin film based low loss magnetically tunable bandpass filter in the flip chip configuration is fabricated. Cobalt ferrite thin film was synthesized by ultrasonic assisted chemical vapor deposition technique on the quartz substrate. This was overlaid on a resonator appropriately coupled to 50 Ω feed lines. The initial operating frequency (resonance frequency) of the bandpass filter was 13.8 GHz which was shifted to 12.82 GHz when a small magnetic field (~150 Oe) was applied showing a tunability of ~7%. A large variation in the tunability of the coupled filter is attributed to change in the permeability of the CFO thin film on the application of magnetic field.

Synthesis and characterization of a heterobimetallic Cu–Zr complex for deposition of 1:1 CuZrO3–CuO composite thin films

A well-defined heterobimetallic complex, [Cu4Zr2(μ4-O)2(dmae)4(OAc)8]·2H2O 1 where dmae=N,N-dimethylaminoethanolato and OAc=acetato, has been constructed by the chemical reaction of Cu(OAc)2·2H2O with Zr(dmae)4 in THF. Complex 1 was characterized by its melting point, elemental analysis, infrared spectroscopy, thermogravimetric analysis and single crystal X-ray diffraction. X-ray crystallography shows that complex 1 crystallizes in the monoclinic space group P21/n with the cell dimensions a=14.7414(5), b=11.7378(4) and c=14.8196(5)Å and β=94.826(2)°. The nature of the thermolysis of 1 showed its aptitude to give a 1:1 CuZrO3:CuO composite oxide material at 575°C. The high solubility and stability of 1 in common organic solvents suggest its efficacy as a single source precursor (SSP) in the aerosol assisted chemical vapor deposition technique for the formation of a CuZrO3–CuO composite thin film on a soda lime glass substrate under an air atmosphere. Thin film properties, such as crystallinity, identification of deposited phases, surface morphology and chemical compositions were probed by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis, which ascertained the evolution of good quality crystalline hemispherical architecture composite oxide thin films from 1.

Photoelectrochemical properties of morphology controlled manganese, iron, nickel and copper oxides nanoball thin films deposited by electric field directed aerosol assisted chemical vapour deposition

An efficient deposition method of the morphologically controlled oxides of manganese (Mn2O3), iron (α-Fe2O3), nickel (NiO) and copper (CuO) spherical shaped nanoball thin films was developed by an in-house built electric field directed aerosol assisted chemical vapour deposition (EFDAACVD) technique. The Mn2O3, α-Fe2O3, NiO and CuO thin films were grown by using a single source precursor, metal acetate, under the application of an electric field that induces the formation of nanoballs of metal oxide thin films with controlled morphologies. The EFDAACVD-produced metal oxide thin films were characterized by using various suitable analytical characterization techniques. The photoelectrochemical properties of the EFDAACVD-produced Mn2O3, α-Fe2O3, NiO and CuO thin films were investigated in the presence of 0.1M Na2SO4 under illumination of simulated solar irradiation of AM 1.5G (100mW/cm2). The charge transfer dynamics of the thin films were also explored using electrochemical impedance spectroscopic (EIS) technique.