Vanadium Pentoxide Thin Films Research Articles

Effect of F-doping on temperature dependence of resistivity of vanadium pentoxide thin films prepared by spray pyrolysis

This paper reports structural and electrical characteristics of F-doped [Formula: see text]V2O5 thin films of different F concentrations. The films were analyzed by X-ray diffraction. It was found that F-doping in vanadium pentoxide affects the crystallinity of the samples. The SEM images have shown that by increasing the F-doping level, the size of the nanobelt increases. Electrical measurements indicated that the F-doping in [Formula: see text]V2O5 makes the temperature of phase transition change from semiconductor to metallic phase.

Sol-gel deposition and characterization of vanadium pentoxide thin films with high TCR

Vanadium pentoxide thin films have been deposited on quartz substrates via sol-gel synthesis and dip coating. The process was developed to establish a reliable and inexpensive method to produce thin films with a high temperature coefficient of resistance (TCR) for sensing applications. Sol-gel precursor concentration and post-deposition annealing conditions were varied to address their effects on film composition, morphology, structure, resistivity, and TCR response. The resulting thin films were structurally characterized by thin film profilometry, x-ray diffraction, scanning electron microscopy, and Raman spectroscopy. Resistivity and TCR measurements were carried out to determine their efficacy as sensor materials. Both low and high concentration alkoxide sol-gel precursors led to films of pure α-V2O5 composition but with characteristically different structural and electrical properties. Low concentration films showed a modest decrease in resistivity and TCR with increasing annealing temperature, consistent with the formation of increasing grain size and the coalescence of largely planar grains with common crystalline orientation. In contrast, films fabricated from higher alkoxide precursor concentration are characterized by a higher density of grains with a larger dispersion in orientation and better-developed grain boundaries, leading to a general increase in resistivity and TCR with annealing temperature. The TCR of the films lied in the range of -3%°C−1 to -4%°C−1, comparing favorably with films produced through conventional techniques such as DC magnetron sputtering, chemical vapor deposition, or pulsed laser deposition. Further, their TCR and resistivity characteristics can be controlled through sol-gel precursor concentration and post-deposition annealing temperature, indicating that sol-gel deposited vanadium pentoxide films are promising candidates for infrared sensor applications.

Optical Properties of vanadium pentoxide prepared by sol gel method

Vanadium pentoxide (V2O5) thin film were deposited using the sol-gel technique. An aqueous solution of V2O5was used for depositing the thin films on glass substrates. The structural and optical characteristics of both non-annealed and annealedV2O5 thin films were examined with X-ray diffraction (XRD) and double-beam UV-visible spectrophotometry. The X-ray diffraction study of the V2O5thin films revealed a mixture of amorphous and polycrystalline nature. The dispersion of the refractive index is discussed in term of Wlemple-DiDomenico single oscillator model, many dispersion parameters such as single oscillator energy (Eo ),dispersion energy ( Ed ), refractive index ( n(0) ), were discussed using Miller’s rule, the optical absorption at the fundamental absorption edge dielectric constant (e¥), moment of the dielectric constant optical spectrum( M-1 ,M-3 )and energy gap by Wimple-DiDomenico approximation ( )have been calculated, non- linear optical susceptibility ( ) has been discussed, direct energy gap by Tauc relation ( ), and Urbach energy of the localized states (Eu) were also calculated. The results were found to be consistent with the data of the previous studies carried out on V2O5 thin films.https://doi.org/10.31257/2018/jkp/100101

X- and gamma-ray irradiation effects on vanadium pentoxide thin films

Thickness and composition of thin films can be measured with X- and gamma-rays. In this work, thickness and composition of vanadium pentoxide thin films are investigated by energy dispersive and wavelength dispersive X-ray fluorescence systems. Also, the surface analysis of vanadium pentoxide thin films irradiated with Rhodium Kα X-rays and 59.54 keV gamma-rays emitted from 100 mCi and 5 Ci Americium-241 radioactive sources is performed by scanning electron microscope. It is observed that X- and gamma-rays are destructive for vanadium pentoxide thin films. Also, the composition of vanadium pentoxide thin films changes by irradiation with X- and gamma-rays.

High sensitivity vanadium–vanadium pentoxide–aluminium metal–insulator–metal diode

This work reports on the fabrication of an improved sensitivity metal–insulator–metal (MIM) diode. They devise an asymmetric structure diode that cascades vanadium, vanadium pentoxide, and aluminium (V–V2O5–Al) thin film layers. The MIM diode is fabricated using electron-beam lithography, sputter deposition and metal liftoff techniques. X-ray photoelectron spectroscopy analysis is performed to determine the phase composition of the V2O5 insulating thin film. Electrical characterisation of the fabricated V–V2O5–Al shows a clear high sensitivity at −316 mV that reaches −8.52 V−1 with a dynamic resistance of 5.024 kΩ.

Effect of hydrogenation on the optical properties and internal electrochromism in vanadium pentoxide xerogel films

The paper describes the effect of hydrogenation of vanadium pentoxide thin films by plasma-immersion ion implantation on their composition, optical properties, and the internal electrochromic (IEC) effect. Variations in the composition and structure caused by the hydrogen insertion, as well as those caused by the electrochromic effect, are studied by nuclear magnetic resonance, thermogravimetry, Raman spectroscopy, and X-ray structural analysis. It is shown that, during electrochromic coloration, if the cathode is located on the non‑hydrogenated region of the film, and the anode is on the hydrogenated region, the IEC effect is more pronounced. This is due to the fact that the migration of protons from the region enriched with hydrogen is considerably greater than that from the pristine non‑hydrogenated region. Thus, the ion implantation-induced hydrogenation can substantially enhance the manifestation and performance of the IEC effect in V2O5 xerogel films. Particularly, the rate of coloration increases by 2–3 times after ion-implantation-assisted hydrogenation as compared to that in the as-prepared non‑hydrogenated films.

Optical and sensing properties of sol-gel derived vanadium pentoxide thin films with porous and dense structures

The sol-gel and spin-coating methods were used for deposition of thin transparent V2O5 films on optical glass substrates and silicon wafers. Different synthesis and deposition conditions, including synthesis temperatures and post-deposition annealing, were used aiming at obtaining transparent films with high refractive index and good optical quality. The surface morphology and structure of the films were studied by SEM and XRD. The optical properties (refractive index, extinction coefficient and optical band gap) and thickness of the V2O5 films were determined from their transmittance and reflectance spectra. The potential application of the films as building blocks of optical sensors was demonstrated by preparation of multilayered structures comprising both V2O5 and BEA-type zeolite films and testing their response towards acetone vapors.

Electronic Structure of C60/Zinc Phthalocyanine/V₂O₅ Interfaces Studied Using Photoemission Spectroscopy for Organic Photovoltaic Applications.

The interfacial electronic structures of a bilayer of fullerene (C60) and zinc phthalocyanine (ZnPc) grown on vanadium pentoxide (V2O5) thin films deposited using radio frequency sputtering under various conditions were studied using X-ray and ultraviolet photoelectron spectroscopy. The energy difference between the highest occupied molecular orbital (HOMO) level of the ZnPc layer and the lowest unoccupied molecular orbital (LUMO) level of the C60 layer was determined and compared with that grown on an indium tin oxide (ITO) substrate. The energy difference of a heterojunction on all V2O5 was found to be 1.3~1.4 eV, while that on ITO was 1.1 eV. This difference could be due to the higher binding energy of the HOMO of ZnPc on V2O5 than that on ITO regardless of work functions of the substrates. We also determined the complete energy level diagrams of C60/ZnPc on V2O5 and ITO.

Effect of Post Annealing on the Structural Properties of Vanadium Oxide Thin Film Deposited by RF Sputtering

Objective: To deposit the highly crystalline thin film of vanadium pentoxide on Si substrate. Method: In this work, we deposited vanadium oxide thin films by RF sputtering setup. These deposited thin films were annealed at 500°C for 1 hour in argon atmosphere. Grazing Incidence X-Ray Diffraction (GIXRD), Raman Spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR) are used to analyze structural properties of as-deposited and annealed thin films of vanadium oxide. Finding: GIXRD spectra of annealed film revealed that highly crystalline thin film of vanadium pentoxide (V2 O5 ) is obtained. The texture of the film is oriented along c- axis, perpendicular to the surface of the Si substrate and it’s a, b axis are parallel to the surface of substrate. Raman Spectroscopy and FTIR results confirmed the layered structure of the annealed vanadium pentoxide thin film. After post annealing, the highly crystalline and layered structure of V2 O5 thin film on Si substrate is obtained. Applications: Vanadium pentoxide thin films are used in electrochromic devices, lithium batteries, and energy storage devices and as toxic gas sensors. Keywords: Vanadium Pentoxide (V2 O5 ), Grazing Incidence X-Ray Diffraction (GIXRD), Raman Spectroscopy, RF Sputtering

$$\hbox {V}_2\hbox {O}_5$$ V 2 O 5 Thin Films Deposited by Sol–Gel and Indigenously Developed Spin Coating System

Thin films of vanadium pentoxide ( $$\hbox {V}_{2}\hbox {O}_{5}$$ ) were deposited on biomedical glass strips and fluorine-doped tin oxide glass substrates by sol–gel and indigenously developed spin coating system. The physical properties such as structural, thermal, optical and electrochemical properties of $$\hbox {V}_{2}\hbox {O}_{5}$$ thin films were investigated. X-ray diffraction of the film annealed in air at the temperature of $$400\,^{\circ }\hbox {C}$$ showed preferred orientation along with (0 0 1) planes lying parallel to the substrate, whereas the changes in annealing temperature caused an increase in transmission spectral region, and TGA curve shows that the weight loss of dry gel occurs at temperature $$370\,^{\circ }\hbox {C}$$ due to evaporation of the water lies within the layers of $$\hbox {V}_{2}\hbox {O}_{5}$$ crystals, which are accompanied by small endothermic peak appeared at $$122\,^{\circ }\hbox {C}$$ and deep endothermic peak at $$313\,^{\circ }\hbox {C}$$ in DTA curve. Electrochemical performance of the annealed $$\hbox {V}_{2}\hbox {O}_{5}$$ thin film was investigated by cyclic voltammetry.

Influence of Li+:V2O5 doping on Nb2O5 thin films electrochemical performance

ABSTRACTAiming to improve electrochromic properties of niobium pentoxide (Nb2O5) there were synthesized new, doped with lithium trifluoromethane sulfonate salt (LiCF3SO3), and vanadium pentoxide (Nb2O5:Li+:V2O5) thin films. A study of these films focused on influence of doping on the electrochromic performance of these films. It was observed that Nb2O5:Li+:V2O5 presents a reversible and fast insertion/extraction kinetics. A maximum charge density for three layers' film was −36.0 mC cm−2, and it corresponded to spectral transmission change of ΔT = 66%, i.e., variation from 80 to 20% from transparent to colored states.

Orbital orientation mapping of V2O5 thin films

We report the effects of growth methods on the orbital orientation in vanadium pentoxide (V2O5) thin films, an important factor to consider when selecting growth techniques for highly selective catalysts and devices. Thermal evaporation and sol-gel methods were used to synthesize the V2O5 films. The surface morphology, roughness, and orientation of the films were characterized by atomic force microscopy and x-ray diffraction. Surface electronic properties and oxidation states were assessed by x-ray photoemission spectroscopy. Polarized x-ray absorption spectroscopy demonstrated that the thermally evaporated film [which was in the (001) orientation] exhibited greater anisotropy than the (100) oriented sol-gel film. The observed increase in anisotropy agrees well with computational findings which revealed that more vanadyl bonds are present at the surface of the thermally evaporated film than at the surface of the sol-gel film. The same computational study also found that the orientation of these bonds is more parallel to the film surface in the thermally evaporated film than in the sol-gel film. The data suggest that the method of growth may be used as a controlled variable to select key film characteristics for potential applications.

Electrical and Infrared Optical Properties of Vanadium Oxide Semiconducting Thin-Film Thermometers

A synthesis method has been developed for preparation of vanadium oxide thermometer thin film for microbolometer application. The structure presented is a 95-nm thin film prepared by sputter-depositing nine alternating multilayer thin films of vanadium pentoxide (V2O5) with thickness of 15 nm and vanadium with thickness of 5 nm followed by postdeposition annealing at 300°C in nitrogen (N2) and oxygen (O2) atmospheres. The resulting vanadium oxide (VxOy) thermometer thin films exhibited temperature coefficient of resistance (TCR) of −3.55%/°C with room-temperature resistivity of 2.68 Ω cm for structures annealed in N2 atmosphere, and TCR of −3.06%/°C with room-temperature resistivity of 0.84 Ω cm for structures annealed in O2 atmosphere. Furthermore, optical measurements of N2- and O2-annealed samples were performed by Fourier-transform infrared ellipsometry to determine their dispersion curves, refractive index (n), and extinction coefficient (k) at wavelength from 7000 nm to 14,000 nm. The results indicate the possibility of applying the developed materials in thermometers for microbolometers.

Naturally formed ultrathin V2O5 heteroepitaxial layer on VO2/sapphire(001) film

Vanadium dioxide (VO2) and vanadium pentoxide (V2O5) thin films change their properties in response to external stimuli such as photons, temperature, electric field and magnetic field and have applications in electronics, optical devices, and sensors. Due to the multiple valence states of V and non-stoichiometry in thin films, it is challenging to grow epitaxial, single-phase V-oxide on a substrate, or a heterostructure of two epitaxial V-oxides. We report the formation of a heterostructure consisting of a few nm thick ultrathin V2O5 epitaxial layer on pulsed laser deposited tens of nm thick epitaxial VO2 thin films grown on single crystal Al2O3(001) substrates without post annealing of the VO2 film. The simultaneous observation of the ultrathin epitaxial V2O5 layer and VO2 epitaxial film is only possible by our unique reflection high energy electron diffraction pole figure analysis. The out-of-plane and in-plane epitaxial relationships are V2O5[100]||VO2[010]||Al2O3[001] and V2O5[032¯]||VO2[100]||Al2O3[11¯0], respectively. The existence of the V2O5 layer on the surface of the VO2 film is also supported by X-ray photoelectron spectroscopy and Raman spectroscopy.

Influence of the crystalline nature of growing surface on the properties of vanadium pentoxide thin films

Vanadium pentoxide (V2O5) thin films have been deposited by reactive direct current (DC) magnetron sputtering onto glass and Si (100) substrates in identical deposition conditions and investigated for their physical properties. The films deposited on glass substrates were amorphous whereas the film deposited on Si substrates were polycrystalline (orthorhombic crystal structure and strong (411) orientation plane). The core level spectrum of the film showed V2p1/2 and V2p3/2 peaks at the binding energy 517.18 and 524.38 eV respectively whichconfirmed the presence of V2O5. The films exhibited a nanosheet-like surface morphology grown normal to the substrate (Si and Glass). The optical bandgap value of the films deposited on glass and Si substrates was found to be in the range of 2.5–3.49 eV and 1.72–2.45 eV respectively. V2O5 films deposited on glass and Si (100) exhibited a temperature coefficient of resistance (TCR) of −0.6 and −1.8%/°C respectively.

Flexible vanadium oxide film for broadband transparent photodetector

A High-performing transparent and flexible photodetector was achieved by reactive sputtering method. Vanadium pentoxide (V2O5) thin films were deposited on flexible polyethylene terephthalate (PET) substrates at room temperature. The transparent and flexible photodetectors with the configurations V2O5/ZnO/ITO/PET showed high-performing photoresponse with a quick response time (4.9 ms) and high detectivity of 1.45 × 1012 Jones, under a light intensity of 1 mW/m2. We demonstrated high-performing V2O5 film-based transparent and flexible broadband photodetectors which may provide a promising approach for transparent electronic applications.

Oxygen and temperature effects on the electrochemical and electrochromic properties of rf-sputtered V2O5 thin films

Vanadium pentoxide (V2O5) thin films grown by rf-sputtering have been studied as a function of two growth parameters, O2 content and substrate temperature, which influence importantly their structural, as well as their electrochemical and electrochromic properties. The increase in O2 content appears to result in an increase of the grain size of the films, while the increase in substrate temperature leads in platelets perpendicular to the substrate, which enhance the porosity of the films. Films with low O2 content (3%) and films grown at a substrate temperature of 300°C, present enhanced charge storage properties of 553mA h g−1 and large transmittance modulation ability. On the contrary, high O2 content (11%) and a substrate temperature of 150°C lead to improved coloration efficiency (at λ=400nm), reaching values of 84.5 and ∼132cm2C−1, respectively. These findings are discussed in terms of structural and morphological changes occurring during the two parameters studied.

Sprayed vanadium pentoxide thin films: Influence of substrate temperature and role of HNO3 on the structural, optical, morphological and electrical properties

Spray pyrolysis technique was employed to deposit vanadium pentoxide thin films at different substrate temperature of 300°C, 325°C, 350°C, 375°C and 400°C from nitric acid added ammonium meta vanadate aqua precursor solution. X-ray diffraction analysis of the deposited films showed the formation of orthorhombic vanadium pentoxide phase with growth along (101) plane. Average crystallite size showed variation from 21 to 42 nm as a function of substrate temperature. The film deposited at 400°C acquired average visible transmittance of ∼77% in the 500–800nm range. Direct optical band gap of the vanadium pentoxide thin film was slightly increased from 1.98 to 2.05eV. Field emission scanning electron microscope and atomic force microscope studies showed that the size and shape of the flakes formed on the surface of the film deposited from the nitric acid added ammonium meta vanadate precursor solution were effectively modified with increase in substrate temperature. The carrier concentration and conductivity of the film deposited at 375°C respectively is 2.138×1013cm−3 and 1.0×10−5Ω−1cm−1 which are relatively high when compared to other films. Photoluminescence spectra of the vanadium pentoxide films deposited at 375°C and 400°C showed intense emission peaks at 475nm and 552nm.

Influence of the Nb2O5 doping on the electrochemical properties of V2O5 thin films

Aiming to improve electrochromic properties of vanadium pentoxide (V2O5) new niobium-doped vanadium pentoxide (V2O5:Nb2O5) thin films were obtained by combining sol–gel method with dip-coating technique. The sols were synthesized by reacting vanadium (V) oxytripropoxide and niobium ethoxide (V) with 2, 5, and 10mol% of Nb sol concentrations as precursors. The films were deposited on a FTO conducting glass substrates and heat treated at 300°C. Cyclic voltammetry characterization of V2O5 and V2O5:Nb2O5 films revealed two cathodic and two anodic peaks that fused in one with increase of scan rate up to 50mV/s. Chronoamperometry showed that the doped samples are more stable than undoped ones. Chronocoulometry measurements proved that the best values of charge density of about 80 mC/cm2 was obtained for the film doped with 5mol% of Nb sol. UV–Vis spectroscopy confirmed 47% transmittance difference at 633nm between colored and bleached states of doped sample, which was 6% more than for undoped one. The characterization of the Nb intercalated V2O5 deposits was done combining energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), proving a possibility of synthesis of structured niobium intercalated vanadium oxides. Moreover, scanning electron microscopy (SEM) morphology and atomic force microscopy (AFM) topography analyses evidenced uniform and smooth surface of the films with more granules on the surface of the doped sample and the RMS values of 9.66 and 3.45nm for V2O5:Nb2O5 and V2O5 film, respectively. V2O5:Nb2O5 electrochromic films have shown improved electrochemical stability and transmittance difference between colored and bleached values, when compared to pure vanadia films.

Thin films of V2O5/MoO3 and their applications in electrochromism

Pure and doped vanadium pentoxide (V2O5, V2O5/MoO3) thin films were prepared by sol-gel method and dip coating technique. Furthermore, they were characterized by chronocoulometry, cyclic voltammetry (CV), UV-Vis, atomic force microscopy (AFM), X-ray diffraction (XRD), and perfilometry. The best results were obtained with V2O5/MoO3 5 mol% film, which showed highest ion storage capacity of ~92 mC cm−2 when compared to other films. Moreover, this film showed optical modulation of 40% at 633 nm after coloration and bleaching for 60 s. XRD patterns revealed that the film has orthorhombic crystalline structure; AFM and perfilometry confirmed roughness and thickness of 4.38 and 554 nm, respectively.