Niobium Oxide Thin Films Research Articles

Amorphous niobium oxide thin films

Amorphous niobium oxide thin films were deposited by unbalanced reactive magnetron sputtering under different conditions of pressure (2 to 4 Pa) and oxygen percentage (9, 17, and 23%). The films were characterized to obtain the relationships between the deposition parameters and the most relevant physical properties (structural, optical, mechanical, surface morphology and optical). The composition was determined by Rutherford backscattering spectroscopy and energy dispersive X-ray spectroscopy. From the results of X-ray diffraction and the composition, we can conclude that for all of the deposition pressures and flow ratios used, the films were stoichiometric Nb 2O 5 and amorphous. Similarly, the mechanical and optical properties did not show significant variation between the different deposition conditions; all the films were transparent with a bandgap of about 3.4 eV and a hardness around 5 GPa. Concerning the electrochemical properties, the response of the films to DC polarization in a 0.89% NaCl solution was significantly different. The parameters used to compare the electrochemical response were the polarization resistance and the corrosion resistance obtained from the Tafel analysis.

Comments on the processing of the niobium component for chemical solution derived niobium oxide-based thin-films

The impact of chemical precursor modification on the electronic properties of chemical solution deposition derived niobium oxide thin-films has been evaluated. It has been found that the application of certain chemical modifications is mandatory in order to obtain electrically insulating thin-films at low processing temperatures. It is emphasized that the devised optimal way of processing for the niobium component is widely contrary to the solution based processing of potassium sodium niobate films reported so far. Regarding the physical nature of the observed instabilities, the phase evolution of solution processed niobium oxide films has been studied. It has been detected that the organic fraction in the precursor solution is stable up to high temperatures and as a result, the low temperature crystalline TT-phase of niobium oxide is preserved up to unusually high processing temperatures. The inherent structural distortion of the unit cells may present a new defect mechanism that has to be further investigated regarding the inferior ferroelectric properties of chemical solution derived potassium sodium niobate thin-films, which are often observed.

Mechanical and thermoelastic characteristics of optical thin films deposited by dual ion beam sputtering

Mechanical and thermoelastic properties of optical films are very important to ensure the performance of optical interference filters and optical coating systems. We systematically study the growth and the mechanical and thermoelastic characteristics of niobium oxide (Nb(2)O(5)), tantalum oxide (Ta(2)O(5)), and silicon dioxide (SiO(2)) thin films prepared by dual ion beam sputtering. First, we investigate the stress (sigma), hardness (H), reduced Young's modulus (E(r)), and scratch resistance. Second, we focus on the methodology and assessment of the coefficient of thermal expansion (CTE) and Poisson's ratio (nu) using the two-substrate method. For the high refractive index films, namely, Nb(2)O(5) (n at 550 nm=2.30) and Ta(2)O(5) (n at 550 nm=2.13), we obtained H approximately 6 GPa, E(r) approximately 125 GPa, CTE=4.9x10(-6) degrees C(-1), nu=0.22, and H approximately 7 GPa, E(r) approximately 133 GPa, CTE=4.4x10(-6) degrees C(-1), and nu=0.27, respectively. In comparison, for SiO(2) (n at 550 nm=1.48), these values are H approximately 9.5 GPa, E(r) approximately 87 GPa, CTE=2.1x10(-6) degrees C(-1), and nu=0.11. Correlations between the growth conditions (secondary beam ion energy and ion current), the microstructure, and the film properties are discussed.

Electrochromic behaviour of Nb 2O 5 thin films with different morphologies obtained by spray pyrolysis

Two different procedures to stabilize the precursor NbCl 5 have been applied to obtain Nb 2O 5 thin films by spray pyrolysis. Depending on the procedure used, determined by the way in which the precursor solution was injected into the air stream of the spray nozzle, niobium oxide thin films with different surface morphologies can be obtained. The structural properties of the Nb 2O 5 thin films depend on the post-annealing temperature because as-deposited films are amorphous, independently of the synthesis procedure used. The electrochromic behaviour has been estimated for all films, where monochromatic colouration efficiency (at 660 nm) of 25.5 cm 2/C and a cathodic charge density close to 24 mC/cm 2 were found to give the best results to date for niobium oxide thin films obtained by spray pyrolysis.

Electrochemical Evaluation of Niobium Oxide Thin Films by Impedance Spectroscopy Using Simulated Body Fluids.

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Effect of post annealing treatment on electrochromic properties of spray deposited niobium oxide thin films

Niobium oxide thin films were deposited on the glass and fluorine doped tin oxide (FTO) coated glass substrates using simple and inexpensive spray pyrolysis technique. During deposition of the films various process parameters like nozzle to substrate distance, spray rate, concentration of sprayed solution were optimized to obtain well adherent and transparent films. The films prepared were further annealed and effect of post annealing on the structural, morphological, optical and electrochromic properties was studied. Structural and morphological characterizations of the films were carried out using scanning electron microscopy, atomic force microscopy and X-ray diffraction techniques. Electrochemical properties of the niobium oxide thin films were studied by using cyclic-voltammetry, chronoamperometry and chronocoulometry.

Electrochromic properties of spray-deposited niobium oxide thin films

Niobium oxide thin films were deposited on the glass and fluorine-doped tin oxide (FTO)-coated glass substrates using simple and inexpensive spray pyrolysis technique. Various preparative parameters like nozzle to substrate distance, spray rate, concentration of sprayed solution were optimized to obtain good substrate-adherent and transparent films. Morphological and structural characterizations of the films were carried out using scanning electron microscopy and X-ray diffraction techniques. Electrochemical characterization of the niobium oxide thin films was carried out using cyclic-voltammetry, chronoamperometry and chronocoulometry.

Properties of spray deposited niobium oxide thin films

Niobium Oxide (Nb2O5) thin films were deposited on the glass substrates, using spray pyrolysis technique. During deposition the preparative parameters like nozzle to substrate distance, spray rate, concentration of the sprayed solution were kept constant at optimized values. The effect of substrate (deposition) temperature (varied between 250 to 450°C) and post annealing treatment (at temperature 500°C) on the structural, optical and electrical properties of thin films were studied. Using scanning electron microscopy and X-ray diffraction technique morphological and structural characterizations of the films were carried out. For optical and electrical properties of thin films, optical absorption and two probe electrical resistivity techniques were used. It has been observed that with increase in the substrate temperature films become micro or polycrystalline. Annealed films exhibit higher crystallinity. Other parameters like thickness, electrical resistivity and band gap energy value decrease with increase in substrate temperature.

Ordered Mesoporous Niobium Oxide Film: A Novel Matrix for Assembling Functional Proteins for Bioelectrochemical Applications

The immobilization of cytochrome c (Cyt‐c) in ordered mesoporous niobium oxide thin films is investigated for the first time. The direct electrochemical behavior of Cyt‐c assembled onto the inorganic matrix (see Figure) and the electrocatalytic properties of this assembly are studied. The results open a new doorway for the application of niobium oxides as bioanalytical devices.

Cobalt(II) metallated hematoporphyrin IX and protoporphyrin IX immobilized on niobium(V) oxide grafted on a silica gel surface: electrochemical studies

Abstract Niobium oxide thin film grafted on porous silica gel was prepared and used to immobilize protoporphyrin IX and hematoporphyrin IX. The porphyrins adhered strongly to the surface probably by the COONb chemical bond formed between the porphyrin carboxyl groups and Nb2O5. The immobilized hematoporphyrin IX and protoporphyrin IX, SiO2/Nb2O5/H2HMP and SiO2/Nb2O5/H2PP, respectively, were further metallated by means of in situ reaction with CoCl2 giving rise to SiO2/Nb2O5/CoHMP and SiO2/Nb2O5/CoPP. The effectiveness of the reactions in producing the metallated adsorbed complexes was investigated by electronic absorption spectroscopy. Graphite paste electrodes of the metallated adsorbed porphyrins were prepared in order to study the electrocatalytic reduction of dissolved dioxygen by the cyclic voltammetry technique. The dioxygen eletroreduction was observed at −0.18 and −0.16 V versus SCE in pH 6 for hematoporphyrin and protoporphyrin complexes, respectively. The cathodic peak potentials at different solution pH remained practically constant between pH 4 and 7 for both materials. The current intensities for a fixed potential plotted against dissolved dioxygen concentrations showed linear responses between 2 and 12 ppm.

Electrochemical and Electrochromic Properties of Niobium Oxide Thin Films Fabricated by Pulsed Laser Deposition

Niobium oxide thin films have been successfully fabricated on the indium‐tin oxide coated glasses by pulsed laser deposition in an gas mixture. Films are characterized by X‐ray diffraction and Raman spectrometry. Electrochemical and electrochromic properties of films are examined by cyclic voltammogram and potential step coupled with an in situ charge‐coupled device spectrophotometer. The unique characteristics of absorption spectra of films are observed for the first time, and the optical absorption from the trapped electrons in the surface states plays an important role in the electrochromic phenomenon. © 1999 The Electrochemical Society. All rights reserved.

Pulsed laser deposition of mesoporous niobium oxide thin films and application as chemical sensors

The pulsed laser deposition (PLD) of a mesoporous niobium oxide, Nb-TMS1, and post-hydrothermal treatment result in mesoporous thin films (90 nm–3 μm thick) having what appears to be a three-dimensional disordered hexagonal or `wormhole' structure. These films were characterized by FT-IR spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The mesoporous Nb-TMS1 thin films were employed as the dielectric phase in capacitive-type chemical sensors. These sensors produce a capacitance change upon the reversible absorption of volatile compounds into the molecular sieve pores. The molecular sieve based sensors were exposed to a variety of analytes, including N 2, CO 2, H 2O, NH 3, methanol and acetone. The mesoporous niobium oxide based sensors were found to be particularly good humidity sensors, exhibiting capacitance changes at least 10 times greater than that for N 2, ammonia, methanol and acetone. The Nb-TMS1 based sensors also showed responses to H 2O that were 1000 times greater than for dense Nb 2O 5 based sensors prepared by PLD.

THICKNESS AND OXYGEN PRESSURE DEPENDENT OPTICAL PROPERTIES OF NIOBIUM OXIDE THIN FILMS

The optical properties of niobium oxide thin films in the thickness range between 75 and 200 nm have been studied. The films were deposited by dc magnetron sputtering and it was found that the refractive index, extinction coefficient and the absorption edge were all strongly dependent on the oxygen pressure during sputtering as well as the thickness of the deposited films. In general, the low thickness films had a lower refractive index than the high thickness films. The highest refractive index obtained was 2.46 at a wavelength of 650 nm for the film deposited at an oxygen pressure of 2 mTorr and to a thickness of 200 nm. The low thickness (~ 120 nm) films showed an initial decrease in refractive index, with oxygen pressure increasing above a critical value. The thicker films, however showed the opposite behaviour, increasing initially and decreasing marginally above the same critical pressure. The absorption edge showed a critical value of thickness above and below which it decreased and a critical value of oxygen pressure during sputtering above and below which it increased. The band gap values varied from 3.3 to 3.6 eV with the thinner films showing the higher band gap. The observed behaviour was explained using the single effective Lorentzian oscillator model.

The Adsorption of Methanol,Water and Ethylene on a Niobium Oxide Thin Film

The Adsorption of Methanol,Water and Ethylene on a Niobium Oxide Thin Film

ChemInform Abstract: Electrochromic Properties of Niobium Oxide Thin Films Prepared by DC Magnetron Sputtering.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Electrochromic Properties of Niobium Oxide Thin Films Prepared by DC Magnetron Sputtering

Niobium oxide electrochromic thin films were prepared by reactive dc magnetron sputtering and their electrochromic properties for Li intercalation and durability were studied. Chronoamperometric analyses revealed that the extended space‐charge limited model by Zhang et al. is applicable to films. Crystallized films showed excellent electrochromism and stability over many coloration‐bleaching cycles. The best performance was obtained for films with a substrate temperature of 500°C and an oxygen flow rate of 10 sccm.

Niobium oxide thin films formed by plasma immersion oxygen ion implantation

In analogy to conventional beam-line ion implantation, plasma immersion ion implantation can be combined with a deposition technique to an ion assisted coating process. The structure and composition of a coating and its interface to the substrate can be modified by ion implantation. By means of electron beam evaporation and oxygen plasma immersion ion implantation niobium oxide films were prepared at low substrate temperatures ( <200 °C). The film composition and thickness were determined by Rutherford backscattering spectrometry. The results show that oxygen plasma immersion ion implantation leads to incorporation of oxygen into niobium in several steps, corresponding to niobium oxide phases with different stoichiometries. By contrast to conventional beam-line ion implantation at low pressures, two channels for oxidation can be distinguished, ion implantation of high-energy species and radiation enhanced in-diffusion of low-energy species from the plasma. The latter is driven by thermodynamic forces.

ChemInform Abstract: Electrochromic Properties of Niobium Oxide Thin Films Prepared by Chemical Vapor Deposition.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Tantalum Oxide and Niobium Oxide thin Films Grown by Pulsed Laser Deposition

ABSTRACTAmorphous tantalum pentoxide (Ta2O5) and niobium pentoxide (Nb2O5) thin films were grown from both metal and oxide target by reactive pulsed laser deposition. Film structure and composition were studied as a function of substrate temperature and oxygen pressure. Good quality transparent films were obtained for substrate temperatures greater than 140° C, and O2 pressures of 200 mTorr. Lower temperatures and pressures produced opaque films, associated with lower oxides.

Electrochromic Properties of Niobium Oxide Thin Films Prepared by Chemical Vapor Deposition

Electrochromic niobium oxide thin films were prepared by chemical vapor deposition. The source material was niobium(V) ethoxide. Amorphous niobium oxide thin films were obtained at a substrate temperature 350°C. Reduction and oxidation of the films in a buffer solution resulted in desirable changes in optical absorption. Coulometry indicated that the coloration efficiency was 160 cm2 · C−1.