Zirconia Thin Films Research Articles

Basic photocatalytic activity of [formula omitted] thin films fabricated by a sol-gel method under UV-C irradiation

The photocatalytic activity of zirconia (ZrO2) thin film fabricated by a sol-gel method was investigated using methyl red decomposition under ultraviolet C (UV-C) irradiation. The dependence of ZrO2 photocatalytic properties on annealing temperature was also investigated. The photocatalytic activity of ZrO2 was compared with that of TiO2, a standard photocatalyst material. Zirconia annealed at 500–700 °C has a combined tetragonal and monoclinic crystal structure, while that annealed at 800–980 °C has an almost exclusively monoclinic structure. The photocatalytic activity of ZrO2 annealed at 500–700 °C was found to be higher than that of ZrO2 annealed above 800 °C. The low activity of ZrO2 annealed above 800 °C is considered to result from the increase in interstitial O− states formed by phase transitions, which lead to increased absorption at ∼5.4 eV. The photocatalytic activity of ZrO2 annealed at 500–700 °C was approximately ten times as high as that of TiO2, which suggests that pure ZrO2 with wide bandgap energy is a promising candidate for photocatalysis under UV-C irradiation.

Influence of oxygen ion elementary diffusion jumps on the electron current through the conductive filament in yttria stabilized zirconia nanometer-sized memristor

• Nanometer-sized virtual memristors based on an yttria stabilized zirconia thin film. • Low-frequency flicker noise in the electron current through the conducting filament. • The random motion (drift/diffusion) of oxygen ions/vacancies effect in this current. • Estimates of the root-mean-square value of the current jumps caused by this motion. • The determination of elementary electronic processes in memristor systems. The structure of the electron current through an individual filament of a nanometer-sized virtual memristor consisting of a contact of a conductive atomic force microscope probe to an yttria stabilized zirconia (YSZ) thin film deposited on a conductive substrate is investigated. Usually, such investigation is performed by the analysis of the waveform of this current with the aim to extract the random telegraph noise (RTN). Here, we suggest a new indirect method, which is based on the measurement of the spectrum of the low-frequency flicker noise in this current without extracting the RTN, taking into account the geometrical parameters of the filament. We propose that the flicker noise is caused by the motion (drift/diffusion) of oxygen ions via oxygen vacancies within and around the filament. This allows us to estimate the root mean square magnitude i 0 of the current jumps, which are caused by random jumps of oxygen ions, and the number M of these ions. This is fundamental for understanding the elementary mechanisms of electron current flowing through the filament and resistive switching in YSZ–based memristor devices.

Varied layer thickness improves structural properties of YSZ thin film

In this study, the Yttrium Stabilized Zirconia (YSZ) thin films were deposited on the sapphire substrate (Al2O3) by dip-coating method using simple ethanol-based YSZ suspension. The layer thickness of YSZ films were varied by sintering at 1300°C. Phase change and structural evolution in YSZ films were observed by conducting X-ray diffraction (XRD) analyses. The microstructures and the surface morphology of the deposited films were examined using Atomic Force Microscope (AFM) and Field Emission Scanning Electron Microscope (FESEM). The XRD pattern revealed a phase change from cubic to monoclinic with an increase in YSZ layer thickness. The crystallite size was varied in the range of 9.68–42.98 nm with the changes in the layer thickness. Meanwhile, the AFM image analyses showed a layer thickness-dependent variation in the grain size (205.83–373.77 nm) and the RMS surface roughness (16.72–36.44 nm). The FESEM images of the achieved film exhibited the occurrence of a dense morphology. It was concluded that by controlling the layer thickness of the deposited films, their improved structure and morphology can be achieved.

Plasma-Enhanced Atomic Layer Deposition of Zirconium Oxide Thin Films and Its Application to Solid Oxide Fuel Cells

Zirconium oxides were deposited using plasma-enhanced atomic layer deposition (PEALD) involving (2-(N-methylamino)1-MethylEthyleneCyclopentadienyl)Bis(DiMethylAmino)Zr (abbreviated as CMEN-Zr) and oxygen plasma as zirconium and oxygen sources. The zirconium oxide thin films demonstrate temperature-independent growth rates per cycle of 0.94 A/cycle at 150–215 °C. The deposited ZrO2 thin films were characterized using numerous analytical tools, i.e., X-ray photoelectron spectroscopy for chemical bonding state and composition, X-ray diffraction for crystallinity, atomic force microscopy for surface morphology, field-emission scanning electron microscopy for cross-sectional analysis, spectroscopic ellipsometry and UV–visible spectrophotometry for optical characterization, capacitance–voltage measurements for dielectric constants and atomic defects, and current–voltage characteristics for electrical information. The insulating features of the crystalline and stoichiometric ZrO2 films were implemented in the anode composites to evaluate the influence of ALD-based nano-features on the electrochemical performance of solid oxide fuel cells, with the main emphasis on anode performance. The presence of nanomaterials on Ni/YSZ anode composites is analyzed to determine the negative effects on electrochemical performance and the degradation of cell performance of solid oxide fuel cells (SOFCs). The artificial design was proven to be effective in controlling the cell performance as long as proper material design was adopted in SOFC electrodes.

Ferroelectric properties of pure ZrO2 thin films by chemical solution deposition

Ferroelectricity in pure zirconia (ZrO2) thin films, manufactured on Si (100) substrates via the chemical solution deposition method using all-inorganic aqueous salt precursor, has been demonstrated for the first time. The influence of thickness on the crystalline structure and ferroelectric properties of the thin films were measured and showed that they were strongly affected by the film thickness. The structural data indicated that as the film thickness increased from 30 nm to 50 nm, the m-phase fraction increased, and a phase transition from orthorhombic to cubic and then tetragonal occurred near the main diffraction peak of 30.7°. The lowest m-phase fraction of 15.4% was obtained in the pure ZrO2 film with a thickness of 30 nm, and after 103 field cycling, it exhibited the highest relative permittivity of 39.6 as well as the highest residual polarization of 8.5 μC/cm2.

Structural, optical and wettability properties of zirconium oxide thin films deposited at various helium partial pressure

The aim of the present work is to deposit zirconium oxide thin films by reactive magnetron sputtering on glass substrates. The influence of helium partial pressure on structural, optical and wettability properties are investigated. The structural properties were investigated using X-Ray Diffraction, which shows that the films deposited has (111) peak of Zirconium Oxide. The intensity of the peak increased with the increase in helium partial pressure. UV-Vis-NIR spectrophotometer was used to study the optical properties of the films; the deposited films were transparent and had excellent transmittance of 95%. Surface roughness measured was in the range of 20.9nm to 21.8nm, the roughness of the deposited films decreased with increase in helium partial pressure. The wettability property measured using contact angle goniometer had a maximum contact angle of 94.1°, which proves that the deposited film has hydrophobic property when measured using water.

Photoluminescence and structural properties of zirconium dioxide thin films produced by RF sputtering technique

In this study, Zirconium Oxide (ZrO2) thin films were produced by using radio frequency magnetron sputtering method on glass substrate at various pressures. The effects of growth pressure on the characteristics of grown Zirconia nanostructures were investigated by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Uv-Visible Spectroscopy and Photoluminescence Spectrometry (PL). XRD analysis showed that peaks of the monoclinic and tetragonal phases were more effective at low growth pressure, but different monoclinic phase peaks were present at increasing growth pressures. The surface morphological properties of the films such as average and maximum roughness, changed significantly with increasing growth pressure, and the maximum peak height first increased to 40 nm and then decreased to 20 nm. The optical transmittance of these thin films was examined in the 450–1100 nm wavelength range, covering both the visible and near-infrared spectral range, and it was found to be approximately 95% at 550 nm wavelength, and the optical band gaps were calculated to be approximately 3.26 eV by PL analyses. Uv-Visible spectroscopy analysis showed that the refractive index of the Zirconia films decreases from 2.09 to 1.79 with increasing wavelength of the incident photon. ZrO2 thin films are considered potential materials for transparent electronic devices because of their high transmittance value.

Selective formation of cubic or tetragonal zirconia thin films of transparent, with no use of metal ion stabilizer by heating molecular precursor films under mild conditions

Cubic or tetragonal zirconia thin films of transparent and 100 nm thickness were selectively formed on a quartz glass substrate by heat-treating the molecular precursor films involving Zr(IV) complexes of nitrilotriacetic acid, at 500[Formula: see text]C in air for 1 h. A precursor solution was prepared by a reaction of the ligand and zirconium tetrabutoxide in alcohol under the presence of butylamine. By the addition of H2O2 or H2O into the solution, the spin-coated precursor films were converted to cubic zirconia thin films by the abovementioned procedure. Further, the identical phase was produced also in the case of the electro-sprayed precursor film which was formed by an addition of H2O2 into the solution. On the other hand, the tetragonal zirconia thin film was obtained from a precursor film formed by using a solution dissolving the original Zr(IV) complex of the ligand, without H2O2 nor H2O. The crystal structure of all thin films was determined by using both the X-ray diffraction (XRD) patterns and Raman spectra. Thus, the zirconia thin films of both crystals could be facilely and selectively obtained with no use of hetero-metal ion stabilizers. The XPS spectra of the thin films show that the O/Zr ratio of the cubic phase is 1.37 and slightly larger than tetragonal one (1.29), and also demonstrate that the nitrogen atoms, which may contribute to stabilize these metastable phases at room temperature, of about 5−7 atomic% was remained in the resultant thin films. The adhesion strengths of cubic zirconia thin film onto the quartz glass substrate was 68 MPa and larger than that of tetragonal one, when the precursor films were formed via a spin coating process. The optical and surface properties of the thin films were also examined in relation to the crystal systems.

Investigation of soft X-ray optical properties and their correlation with structural characteristics of zirconium oxide thin films

ABSTRACT Oxide-based compound materials serve as a suitable coating material for soft X-ray optical applications. The optical performances of such materials depend on various properties like oxygen (O)/metal ratio, O-vacancies, defects, and crystallinity. In this study, we have investigated the soft X-ray optical properties and their correlation with structural characteristics of zirconium oxide thin films of thickness ~10 and 50 nm. The soft X-ray optical properties of the films were measured using Indus-2 soft X-ray reflectivity beamline BL-03 covering the O K-edge. To understand the influence of structural parameters, crystallinity, and the local environment of the films on the optical performance, multiple techniques like grazing incidence X-ray reflectivity, diffraction and Extended X-ray Absorption Fine Structure Spectroscopy are used. It was found that a marginal variation in O/Zr ratio, O- vacancies, and a change in distortion and co-ordination number of the Zr-O and Zr-Zr bonding in the two films of different thicknesses does not influence much the behaviour of soft X-ray optical response near O K-edge region. Details of the results are discussed.

Thermal stability of oxygen vacancy stabilized zirconia (OVSZ) thin films

Thermal stability of reactive magnetron sputter deposited oxygen vacancy stabilized cubic zirconia (OVSZ) thin films containing 16 and 3 at.% oxygen vacancies is reported. Temperature-resolved grazing incidence X-ray diffraction (TR-GIXRD) measurements (200–900 °C) in air and nitrogen atmosphere were performed. TR-GIXRD data show that the deposited films are stable up to 750 °C irrespective of the annealing atmosphere or the oxygen vacancy concentration. However, above 750 °C a fraction of zirconia transforms from cubic to monoclinic structure. This structural transition is explained by the compressive stresses, generated as a result of discrepancy in film-substrate thermal expansion coefficients. Thermal cycling of the deposited OVSZ thin films is also performed at 700 °C and show that films retain their initial cubic structure.

Interfacial Regulation of Dielectric Properties in Ferroelectric Hf0.5Zr0.5O2 Thin Films

The discovery of ferroelectricity in hafnium zirconium oxide (HZO) thin films has attracted wide attention from academia to industry due to the application in ferroelectric non-volatile random access memories (FeRAM) with prominent performance in scalability and CMOS process compatibility. Dielectric behavior of ferroelectric HZO thin films is a key factor affecting the dynamic effect, piezoelectric and electrostrictive effect. Interface between HZO and capping electrodes plays an important role in regulating the dielectric properties. In this paper, the impedance frequency response and dielectric spectrum of ferroelectric HZO thin films were analyzed. Parameters of the interface were extracted to analyze the regulating effect on the dielectric properties based on an impedance model with constant phase element (CPE). Besides, dielectric spectrums at elevated temperatures were identified to verify this analysis.

Antiferroelectric titanium-doped zirconia thin films deposited via HiPIMS for highly efficient electrocaloric applications

In this study, the antiferroelectric (AFE) and electrocaloric (EC) characteristics of lead-free titanium (Ti)-doped zirconia (ZrO2) thin films deposited via high-power impulse magnetron sputtering (HiPIMS) were investigated. The argon-to-oxygen ratio was initially optimized during deposition to obtain a more stoichiometric ZrO2 film for enhanced antiferroelectricity. Furthermore, enhanced crystallinity was achieved through the incorporation of Ti atoms into ZrO2 thin films as confirmed via grazing incidence X-ray diffraction and high-resolution transmission electron microscopy. For metal-insulator-metal capacitors with Ti-doped ZrO2 thin films, the AFE behaviors were significantly improved because of the excellent crystallinity of the tetragonal phase. Based on a fast polarization response and robust fatigue resistance under a 106-cycle endurance test, the EC effect was successfully explored, and an adiabatic temperature change (ΔT) of −14.8 K was realized. With competitive EC properties, Ti-doped ZrO2 thin films deposited via HiPIMS are proposed as promising candidates for use in future cooling systems.

Fabrication and characterization of tetragonal yttria‐stabilized zirconia single‐crystalline thin film

AbstractTetragonal yttria‐stabilized zirconia thin film was successfully fabricated by a pulsed laser deposition method. The thin film grew heteroepitaxially with the orientation relationship of ZrO2‖Al2O3. Energy dispersive X‐ray spectroscopy mapping revealed that Y3+ ions were distributed homogeneously without local segregations. X‐ray and electron‐diffraction analysis confirmed a single crystalline structural feature of the film. On the other hand, high‐resolution scanning transmission electron microscopy observations show that this film contains small‐angle tilt grain boundaries, which is composed of the periodic array of dislocations with the Burgers vector .

Preparation of dense ScSZ thin films by plasma spraying with densified ScSZ powders

Low-pressure plasma spray (LPPS) technology was applied to make scania-stabilized zirconia (ScSZ) thin films for solid oxide fuel cell (SOFC). Agglomerated ScSZ powders and densified ScSZ powders sintered at high temperature were synthesized and sprayed to make dense ScSZ thin films in the LPPS processes. SEM results indicate that the densified ScSZ powders can be easier molten in plasma stream to form more uniform and denser thin films. The influence of spraying parameters on the microstructure of the films was investigated. It is found that longer spraying distance was beneficial to the melting of the flying powders to make high-quality thin films. The ionic conductivity of the thin film (about 20 μm thick) was about 0.025 S/cm measured at 700 °C. A half-cell sample was made via air plasma spray process by using the densified ScSZ powder. The result indicated that a denser and thinner ScSZ should be made for higher electrochemical property.

Enhancement of Oxidation of Formic Acid through Application of Zirconia Matrix for Immobilization of Noble Metal Catalytic Nanoparticles

Electrocatalytic activity of common noble metal (platinum, bimetallic platinum-ruthenium and palladium) nanoparticles (both unsupported and supported on Vulcan carriers) toward electrooxidation of formic acid in acid medium (0.5 mol dm–3 H2SO4) can be significantly enhanced by dispersing them over thin film of zirconia (ZrO2). The enhancement effects concern increases of the electrocatalytic current densities (normalized against the mass of noble metal catalysts) recorded under both cyclic voltammetric and chronoamperometric conditions. The observations can be rationalized in terms of the ability of zirconia nanostructures to provide active hydroxyl groups capable of inducing the removal of the inhibiting COOH or CO type adsorbates from their surfaces. The role of Vulcan carriers is in improving electronic conductivity, in addition to facilitating distribution of catalytic metal sites at the electrocatalytic interface. Regarding dissimilar mechanisms for HCOOH oxidations at Pt, PtRu and Pd nanoparticles, the activating capabilities of zirconia differ depending on the potential applied thus reflecting distinct nature of electronic or chemical interactions. Specific interactions between the zirconia support and noble metal nanoparticles are also possible, particularly in the case of Pd-based catalysts where the enhancement effects are the most pronounced. Finally, it should be emphasized that, historically, representatives of Russian school of electrochemistry, including V.S. Bagotsky, were one of the first world-wide who investigated the formic acid oxidation and emphasized the importance of metal—support interactions during electrooxidation of small organic molecules at noble metal nanoparticles.

E-Beam Deposition of Scandia-Stabilized Zirconia (ScSZ) Thin Films Co-Doped with Al

Scandia alumina stabilized zirconia (ScAlSZ) thin films were deposited using e-beam evaporation, and the effects of deposition parameters on the structure and chemical composition were investigated. The analysis of thin films was carried out using Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-Ray Diffraction Analysis (XRD) and Raman spectroscopy methods. It was found that the chemical composition of ScAlSZ thin films was different from the chemical composition of the initial powder. Moreover, the Al concentration in thin films depends on the deposition rate, resulting in a lower concentration using a higher deposition rate. XPS analysis revealed that ZrOx, oxygen vacancies, high concentrations of Al2O3 and metallic Al exist in thin films and influence their structural properties. The crystallinity is higher when the concentration of Al is lower (higher deposition rate) and at higher substrate temperatures. Further, the amount of cubic phase is higher and the amount of tetragonal phase lower when using a higher deposition rate.

Effect of zirconium oxide local structure on soft x-ray optical properties near the oxygen K-edge region

Zirconium oxide thin film serves as one of the potential material candidates in extreme ultraviolet/soft x-ray optics applications. The suitability of its application can be justified by investigating its optical performance in the working energy range. In this study, we have investigated the soft x-ray optical properties of a zirconium oxide thin film near the O K-edge region using the energy-dependent soft x-ray reflectivity (SXR) technique. The SXR and absorption measurements are performed using the Indus-2 soft x-ray reflectivity beamline BL-03. The optical constants (δ and β) in the energy range of 500–560 eV covering O K-edge are extracted by applying Kramers–Kronig relations. Experimentally obtained δ and β profiles show a prominent eg and t2g feature in the vicinity of O K-edge with the crystal field splitting of 2.9 eV. All features observed in the δ and β spectra are correlated with their electronic structure and composition of the zirconium oxide thin film. Details of correlation between structural and optical properties as determined by x-ray absorption spectroscopy, x-ray photoelectron spectroscopy, and SXR analyses are discussed.

Enhancement of oxidation of dimethyl ether through application of zirconia matrix for immobilization of noble metal catalytic nanoparticles

Electrocatalytic activity of Pt and bimetallic PtRu nanoparticles (both Vulcan supported and unsupported) toward electrooxidation of dimethyl ether (DME), a potential small organic molecule fuel, in an acid medium (0.5 mol dm−3 H2SO4) has been significantly enhanced by dispersing them over a thin film of zirconia (ZrO2). The enhancement effects concern increases of the DME electrocatalytic current densities recorded under both cyclic voltammetric and chronoamperometric conditions. Similar effects have been observed for the oxidation of methanol. Regarding the dissimilar DME electrooxidation mechanisms at Pt and PtRu catalytic centers, the activating capabilities of zirconia seem to originate from the high population of reactive –OH groups favoring mobility of protons and the capability of inducing the oxidative removal of poisoning (CO-type) intermediates both at platinum and ruthenium catalytic sites. In the presence of the zirconia matrix, the onset potential for the oxidation of DME (particularly at PtRu) is shifted more than 50 mV toward less positive potentials. Mutual metal-support interactions are also postulated.

Stability of ferroelectric and antiferroelectric hafnium–zirconium oxide thin films

Hafnium–zirconium oxide (HZO) thin films are of interest due to their ability to form ferroelectric (FE) and antiferroelectric (AFE) oxide phases. Density functional theory is employed to elucidate the stabilization mechanisms of both FE HZO thin films and AFE ZrO2 films. The FE orthorhombic phase is primarily stabilized by in-plane tensile strain, which spontaneously occurs during the synthesis process, and this is more effective for HZO than HfO2. Layer-by-layer stack models and core-matrix three-dimensional models of the polymorphs reveal that the electrostatic component of interfacial free energy can play a critical role in the formation of the AFE tetragonal phase in ZrO2 and the “wake-up” effect for FE HZO.

Laser Ablation Ceramic Target for 8YSZ High-k Dielectric Electrolyte thin Films Precessed by PLD on Si(100) and Pt/Si(111)

The cubic structure 8YSZ (8%Yttria-Stabilized Zirconia) thin films deposited by PLD(Pulsed Laser Deposition) on substrates Si (100) and Pt/Si (111) by identical control parameters have potential applications as electrolytes for planar micro electrochemical devices like Lambda oxygen sensors and IT-�SOFC. It appearance differences in polycrystalline structural and optical characterization by XRD (X-ray Diffraction), SEM (Scanning Electron Microscope), AFM (Atomic Force Microscopy) and V- VASE (Variable Angle Spectroscopic Ellipsometry. The differences are relating on crystalline dimensions, lattice parameters; surface roughness measured by V- VASE and AFM are presented synthetic to evidence the differences generated by substrates.