Vanadium Films Research Articles

Three-Dimensional Vanadium and Nitrogen Dual-Doped Ti3C2 Film with Ultra-High Specific Capacitance and High Volumetric Energy Density for Zinc-Ion Hybrid Capacitors.

Zinc-ion hybrid capacitors (ZICs) can achieve high energy and power density, ultralong cycle life, and a wide operating voltage window, and they are widely used in wearable devices, portable electronics devices, and other energy storage fields. The design of advanced ZICs with high specific capacity and energy density remains a challenge. In this work, a novel kind of V, N dual-doped Ti3C2 film with a three-dimensional (3D) porous structure (3D V-, N-Ti3C2) based on Zn-ion pre-intercalation can be fabricated via a simple synthetic process. The stable 3D structure and heteroatom doping provide abundant ion transport channels and numerous surface active sites. The prepared 3D V-, N-Ti3C2 film can deliver unexpectedly high specific capacitance of 855 F g-1 (309 mAh g-1) and demonstrates 95.26% capacitance retention after 5000 charge/discharge cycles. In addition, the energy storage mechanism of 3D V-, N-Ti3C2 electrodes is the chemical adsorption of H+/Zn2+, which is confirmed by ex situ XRD and ex situ XPS. ZIC full cells with a competitive energy density (103 Wh kg-1) consist of a 3D V-, N-Ti3C2 cathode and a zinc foil anode. The impressive results provide a feasible strategy for developing high-performance MXene-based energy storage devices in various energy-related fields.

Corrosion Inhibition of the Zinc Thermo-Diffusion Coating by Vanadate Conversion Coatings

The inhibition of zinc thermo-diffusion coating corrosion by tetravalent vanadium (VIV)-based conversion coating was investigated in this work, aiming at the development of chemical conversion processes. The coated surfaces were examined using SEM, EDS, XPS, corrosion tests in salt spray, and electrochemical impedance spectroscopy (EIS) measurements in order to build a meaningful relationship between the coating element and the evolution of its chemical state when the surface encounters corrosion. VIV conversion coating shows a resistance feature to corrosion, in which zinc thermo-diffusion coating in exposure to salt spray can be protected due to the irreversible formation of a tetravalent–trivalent mixed-state vanadium film layer. From a thermodynamic point of view, the coating layer acts as a reservoir of VIV to fuel passivation, and then active VIV leached from the layer structure can migrate to the newly formed defects and occupy susceptible sites, resulting in the regeneration of a protective barrier layer by partial reduction to trivalent vanadium (VIII) both on the surface and at the defect. Finally, the formation of the VIII layer seems to be essential for the long lifetime of coatings through blocking the aggressive medium and further VIV reduction.

Diffusion of the hydrogen in nanocrystalline vanadium films

The β → α phase transition and diffusion of the hydrogen in nanocrystalline vanadium films were investigated. Films were deposited onto the glass substrate at the temperature 673 K and at room temperature. Transmission electron microscopy investigations of the structure of films showed that the averaged sizes of vanadium crystallites were 7 and 4 nm, respectively. The derivative of the electrical resistance of the saturated film revealed the broad β → α phase transition about 390 K. The diffusion coefficient of the hydrogen was obtained from the approximation of the time dependence of the increase of the electrical resistance of the non-saturated part of the film by an analytical expression. Values of the diffusion coefficient revealed the strong dependence on the concentration of the hydrogen. At small concentration of the hydrogen, the diffusion coefficient was equal to that in the bulk vanadium. At large concentrations of the hydrogen (above 20 at. %), the diffusion coefficient decreases by a thousand times. The activation energy of diffusion, calculated for samples with the large concentration of the hydrogen, is equal to (44.8 ± 0.8) kJ/mol [(0.464 ± 0.008) eV].

Enhancement of phase transition properties of ultrathin VO2 thin films on microsphere array by vacuum thermal pre-annealing

Vanadium dioxide (VO2) thin films were fabricated on SiO2 microsphere array surface by vacuum thermal pre-annealing and rapid thermal oxidization annealing of magnetron sputtering vanadium films. The effects of vacuum thermal pre-annealing temperature on phase transition properties of VO2 thin films were investigated. The resistance transition ranges of phase transition are improved from 7.58 to 10.23 as the increasing of vacuum thermal pre-annealing temperature. The phase transition temperature decreases and the width of thermal hysteresis loop keeps constant. We analyzed the effects of vacuum thermal pre-annealing temperature on phase transition properties of VO2 thin film in the light of vanadium thin film shrinking effects. The results are important for fabrication of ultrathin VO2 film on microsphere array and application in optical regulation field.

Understanding of deposition mechanism of vanadium on LiF with large mismatch by facing target sputtering (FTS)

V/LiF is a significant window material for investigation of phase transition of materials at ultra-high pressure which is a fundamental issue in condensed matter physics. However, the large mismatch of lattice and thermal makes vanadium growth on LiF as big challenge. In this current study, over 1.5 μm thick vanadium films were grown on LiF via facing target sputtering (FTS). The transmission electron microscopy (TEM) observation showed the grown vanadium films feature vertically well-aligned columnar crystals with numerous micro-sized gaps. For understanding the deposition mechanism, the behaviors of plasma discharge, transport of sputtered atoms and growth of films were simulated by particle-in-cell Monte Carlo collision (PIC-MCC) and Kinetic Monte Carlo (KMC) methods, respectively. The growth model of vanadium film was established based on the experimental and simulation results. And the micro-sized gaps of columnar crystals contribute to release residual stresses generated by large mismatch, which can be explained by the grain boundary relaxation model.

A comparative study of the thermochromic performances of VO2 films obtained by air oxidation of V and VN precursors

Thanks to its metal-to-insulator transition (MIT) temperature not so far from the ambient one, thermochromic VO 2 exhibits great potentiality in smart coatings devoted to energy purposes. Among the different methods to synthesize thermochromic VO 2 films, reactive magnetron sputtering remains one of the most suitable for cost-effective industrial-scale production. For a few decades, increasing attention has been paid to a fast and relatively simple approach based on two steps to produce thermochromic VO 2 thin films: synthesis of a vanadium thin film followed by its oxidation at moderate temperatures. Recently, we have revealed that the oxidation of vanadium nitride (VN) thin films also gives rise to the formation of thermochromic VO 2 . This work aims to compare the thermochromic properties of VO 2 films achieved after thermal air oxidation of V and VN thin films. For both precursors, short-time air annealing was performed at 550 °C. X-ray diffraction and Raman spectroscopy depicted that the thermal oxidation domain allowing the formation of the thermochromic VO 2 phase was enlarged for VN compared to V precursor films. These results were confirmed by electrical measurements. Finally, a particular focus was made on the oxides of the VN series in terms of their infrared properties. The results indicate that the oxidation of VN precursor allows the synthesis of VO 2 films with high purity displaying good thermochromic performances (IR contrast of 63%, electrical switch of ∼2 decades) with narrower hysteresis widths (<9.3 °C) as compared to those from vanadium films, making VN precursor of particular interest for industrial upscaling. • Vanadium dioxide thin films have been synthesized after air-oxidation of sputtered VN and V films. • The use of VN precursor allows a better control of the oxidation process. • More efficient thermochromic VO 2 thin films have been obtained by VN oxidation.

Atmospheric flash annealing of low-dimensional vanadium nanolayers sputtered on glass substrates

A simple approach to attain low-dimensional, highly transparent VO2-based thermochromic coatings on glass substrates is reported. This two-step procedure comprises the initial deposition of DC magnetron-sputtered vanadium films and the subsequent flash annealing of such layers in air atmosphere. The careful control of the thermal treatment parameters and characterizations carried out by scanning electron microscopy and variable temperature Vis-NIR spectrophotometry allowed the optimization of VO2 yields for 12.5 nm and 25 nm thick layers. The impact of layer thickness and the nature of the thermal treatment itself on the thermochromic features of such systems were also evaluated. In this sense, the resulting systems developed asymmetric transmittance vs. temperature hysteresis loops as well as a surprisingly advantageous lowering of the phase transition temperature, which is achieved without the incorporation of dopants. The most promising results were obtained for a 12.5 nm thick layer flash annealed at 475 °C, which, despite having a moderate solar modulation ability (∼2%), could be a potential candidate for smart windows applications given its high Vis-NIR transparency (> 60%) coupled with its low transition temperature of 16 °C below the standard value for pure VO2.

Controlling the crystalline orientation and textual morphologies of the VO2 film and the effect on insulator–metal transition properties

Monoclinic VO2 films were prepared over quartz substrates through thermal oxidation of sputtered vanadium films under continuous O2 flow in a vacuum. It was found that an additional vacuum pre-heating before the thermal oxidation could have a great effect on film crystalline orientation and textual morphologies. The film exhibits a preferable growth along [011] direction and consists of uniform small inter-connected nanoparticles, while the untreated film shows (200) orientation and is composed of large irregular nanoparticles that connect via disorder boundaries. The (011) orientated film shows slightly higher full solar and IR light modulations. The electric resistance results also show that the metal–insulator transition (MIT) of the (011) orientated film presents a larger amplitude, higher sharpness, and narrower hysteresis as compared to the (200) orientated film. The difference in textual structures of the orientated films is the main physical reason that affects the MIT of m-VO2 films.

Inner size effect of temperature coefficient of resistance in Cu, Ag, V and Mo films

The work is devoted to the study of the thermal coefficient of resistivity (TCR) in nanocrystalline and amorphous metal films, the thickness of which significantly exceeds the mean free path of charge carriers. It is shown that in films of silver and copper deposited on the substrate at room temperature, TCR is 2∙10−3 K−1 and 1.2∙10−3 K−1 for silver and copper films, respectively. The obtained values are 2–3 times lower than the tabular ones. For nanocrystalline films of vanadium and amorphous films of molybdenum, an anomalous TCR was found, which is observed while maintaining the metallic nature of the conductivity. The values obtained are −6.1∙10−4 K−1 (V) and −4∙10−4 K−1 (Mo). It is shown that the increase in the substrate temperature during films deposition brings the observed values of TCR closer to those, which are typical for the massive state. The found effects are explained by the highly dispersed structure of the samples.

Nanostructured and columnar vanadium and vanadium oxides films synthesized by means of magnetron-based gas aggregation source

In this study the possibility to employ magnetron-based gas aggregation source for the effective and facile production of mesoporous vanadium films composed of individual vanadium nanoparticles is investigated. It is demonstrated that due to the high deposition rate of V nanoparticles under optimized conditions, their low impact energies, and the directionality of the deposition process, it is possible not only to produce porous nanoparticle coatings, but also coatings with columnar structures. Furthermore, it is shown that such produced coatings may be easily transformed into vanadium pentoxide ones by their annealing in air at the temperature of 550 °C, without loosening the mesoporous character of resulting films. • Mesoporous vanadium nanoparticle films were produced by a gas aggregation source. • The architecture of the films may be changed to columnar one by substrate tilting. • The films are transformed to V 2 O 5 ones upon annealing in air at 550 °C. • The structure of the nanoparticle films is preserved during the annealing.

High performance of V2O5 thin film electrodes for lithium-ion intercalation

A reduced toxicity production route of vanadium pentoxide thin films together with the study of the fabrication parameters that allow optimizing the performance of this material as a cathode for lithium-ion batteries is presented. V2O5 films were fabricated on silicon and stainless-steel substrates by combining electron beam evaporation of metallic vanadium film followed by an oxidation process. A strong dependence on their performance as cathodes for LiBs to the film thickness and microstructure was found, the later depending mainly on the oxidation temperature. Particularly, V2O5 electrodes with 150 nm of thickness fabricated from 50 nm of metallic vanadium oxidized at 500 °C, exhibit excellent performance with a reversible and fast Li storage capability, a high average discharge capacity up to 271 mAh/g at 0.5C, very close to the theoretical capacity (294 mAh/g), with near to 100% of coulombic efficiency. First-principles calculations of Li+ diffusion in three main V2O5 crystallographic directions using density functional theory (DFT) were performed to explain how this remarkable performance is related to the film microstructure.

Fabrication and characterization of enhanced hydrazine electrochemical sensor based on gold nanoparticles decorated on the vanadium oxide, ruthenium oxide nanomaterials, and carbon nanotubes composites.

This work describes the synthesis of mixed oxide film of vanadium and ruthenium by pulsed deposition technique on multiwall carbon nanotubes and the decoration of gold nanoparticles on the mixed film. A ternary electrocatalyst has been developed for the electrochemical oxidation of hydrazine by combining two metal oxide mixtures with Au nanoparticles. Surface morphology and chemical composition of the electrode have been examined with SEM, EDX, HRTEM, EIS, and XRD. The peak current of hydrazine increased 9 times at the AuNPs/(VOx-RuOx)/CNT/GCE compared to the bare GCE, and the peak potential shifted to negative 848 mV. Linear sweep voltammetry (LSV) and amperometric techniques revealed that the AuNPs/(VOx-RuOx)/CNT/GCE displays linear concentration range 2.5–10000 µM (LSV) and the concentration range 0.03–100 µM (amperometry). The limit of detection (LOD) is 0.5 μM and 0.1 μM at (S/N = 3) for LSV and amperometric technique, respectively. The results obtained show a good RSD% of 2.1%–3.2% and reasonable recovery of 97%–108% of hydrazine detection.

Thin-film synthesis of superconductor-on-insulator A15 vanadium silicide

We present a new method for thin-film synthesis of the superconducting A15 phase of vanadium silicide with critical temperature higher than 13 K. Interdiffusion between a metallic vanadium film and the underlying silicon device layer in a silicon-on-insulator substrate, at temperatures between 650 and 750 °C, favors formation of the vanadium-rich A15 phase by limiting the supply of available silicon for the reaction. Energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction verify the stoichiometry and structure of the synthesized thin films. We measure superconducting critical currents of more than 106 amperes per square centimeter at low temperature in micron-scale bars fabricated from the material, and an upper critical magnetic field of 20 T, from which we deduce a superconducting coherence length of 4 nm, consistent with previously reported bulk values. The relatively high critical temperature of A15 vanadium silicide is an appealing property for use in silicon-compatible quantum devices and circuits.

Nanoindentation study in cold gas dynamic sprayed thin films using molecular dynamics simulation

Abstract To enhance the efficiency of the cold gas dynamic spray (CGDS) technology-based metal composite membrane, it is extremely important to examine the mechanical characteristics of the CGDS coated thin films at the atomistic level. The nanoindentation test was performed in the present study on vanadium, copper and palladium thin film coated on niobium substrate by using molecular dynamic (MD) simulation. At the indentation region, the thermosetting control is applied with temperature variance from 300 K to 700 K. The results show that as the temperature decreases, the indentation load increases for loading and unloading processes. nanoindentation test was also performed at a different nanoindentation loading rate of 0.5–2.5 A/ps. The measured average hardness of the thin films by nanoindentation method increases in the order of vanadium, copper and palladium with the nanoindentation loading rate.

Deposition and corrosion behavior of -oriented vanadium thick films by direct current magnetron sputtering

The highly oriented vanadium thick film is the ideal diffraction target of synchrotron X-ray diffraction and optical analyzer technique for investigation of phase transition at high pressure. In this study, the <110>-oriented V film with thickness over 2 μm was deposited by direct-current magnetron sputtering. The effects of working pressure (P) and target-to-substrate distance (d) on phase structure, surface morphology, microstructure, and corrosion resistance of the film were investigated. The results show that the vanadium film with the P of 1.0 Pa and the d of 70 mm is highly <110> preferred orientation. The film crystallinity decrease with the increase of P and d. As the P and d increase, the film deposition rate decreases. When the P increases from 1.0 Pa to 2.0 Pa, the corrosion resistance of the film is significantly improved, and the polarization resistance increases by an order of magnitude. However, as the pressure increases further to 2.5 Pa, the film will fall off in the corrosive medium. When the d increases, the corrosion resistance of the film will also be improved.

Microstructure and Oxidation Resistance of V Thin Films Deposited by Magnetron Sputtering at Room Temperature

Vanadium films were deposited on Si(100) substrates at room temperature by direct current (DC) magnetron sputtering. The microstructure and surface morphology were studied using scanning electron microscopy (SEM) and atomic force microscope (AFM). The oxidation resistance of films in air was studied using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results showed that the amorphous vanadium film with a flatter surface had higher oxidation resistance than the crystalline film when exposed to atmosphere. The rapid formation of the thin oxide layer of amorphous vanadium film could protect the film from sustained oxidation, and the relative reasons were discussed.

STRUCTURE OF V-Mо-SiO2 BRAGG REFLECTOR OBTAINED &#x0D; BY MAGNETRON SPUTTERING

The results of the study of the composition and chemical state of the coating of samples of Bragg reflectors based on films of molybdenum (Mo), vanadium (V), silicon dioxide (SiO2) and aluminum (Al) formed by direct current magnetron sput-tering in an argon atmosphere are presented. The effect of sputtering on the surface of silicon oxide films, as well as surface etching, has been studied. The reasons that affect the adhesion and roughness of the surfaces of thin-film layers of the Bragg reflector are determined.

A Molecular Dynamics Investigation of the Temperature Effect on the Mechanical Properties of Selected Thin Films for Hydrogen Separation

In this study, we performed nanoindentation test using the molecular dynamic (MD) approach on a selected thin film of palladium, vanadium, copper and niobium coated on the vanadium substrate at a loading rate of 0.5 Å/ps. The thermosetting control is applied with temperature variance from 300 to 700 K to study the mechanical characteristics of the selected thin films. The effects of temperature on the structure of the material, piling-up phenomena and sinking-in occurrence were considered. The simulation results of the analysis and the experimental results published in this literature were well correlated. The analysis of temperature demonstrated an understanding of the impact of the behaviour. As the temperature decreases, the indentation load increases for loading and unloading processes. Hence, this increases the strength of the material. In addition, the results demonstrate that the modulus of elasticity and thin-film hardness decreases in the order of niobium, vanadium, copper and palladium as the temperature increases.

Influence of rare earth doping concentrations on the properties of spin coated V2O5 thin films and Cu/Nd-V2O5/n-Si Schottky barrier diodes

In the present work, Nd(x)-V2O5-nanorods (x = 2, 4 and 6 wt%) thin films were prepared via a spin coating technique. X-ray diffraction analysis shows tetragonal phases for neodymium substituted films. The concern diffraction angle shifted to higher angle owing to substitution in vanadium that implies complete occupation in V2O5 crystal lattice. FE-SEM images are flaunting one dimensional nano-rod formation. Conductivity analysis of fabricated diode at different temperature reveals their activation energies (Ea) and these energies are high when rare earth interfaced diode in contrast to pure vanadium films. The essential current (I) and voltage (V) characteristics of junction diodes express nonlinear behaviour. The photodiode parameters like n, ФB, I0, Ps, R, QE and D* are calculated by dark and light condition. The photodiode performance under lighting condition is superior than dark.

Wafer-size VO2 film prepared by water-vapor oxidant

The growth of wafer-scale and uniform monoclinic VO2 film with excellent phase transition property was a challenge if considering the multivalent nature of vanadium atom and the various phase structures of VO2 compound. Direct oxidation of metallic vanadium film by annealing in oxygen gas or in air was suggested to be an easy way for VO2 film preparation, while the oxidation parameters including the gas pressure, gas flux and annealing temperature were extremely sensitive due to the critical preparation window. Here we proposed a facile water-vapor assisted thermal oxidation to produce wafer-scale VO2 films with good uniformity. Results indicated that by using the water vapor as the oxidizing agent, the temperature window for VO2 growth was greatly broadened. In addition, the obtained wafer-size VO2 film showed very uniform surface and sharp resistance change, which was attributed to the improved crystallinity and the high oxygen stoichiometry. The chemical reaction route was calculated based on Gibbs free energy, which confirmed the preferred growth of VO2 film by wet oxidation. Our results not only demonstrated that the water vapor could be used as a modest oxidizing agent, but also showed the unique advantage for large size VO2 film preparation, which was useful for practical devices applications in the future.