Properties Of Zirconia Thin Films Research Articles

Cubic phase optimization and influence of post-annealing on microstructure, optical, wetting, and nanomechanical properties of zirconia thin films

This work reports the fabrication of zirconia thin films by e-beam deposition, followed by thermal annealing in air at different temperatures to optimize the cubic phase without using any dopants or chemical stabiliser. The X-ray diffraction (XRD) and Raman spectra of zirconia films annealed at 500 °C reveal the formation of stable cubic phase with a crystallite size of 10.7 ± 0.8 nm at room temperature. Optical transparency of the zirconia film annealed at 500 °C is high, approaching 80% in the visible range. Increasing annealing temperature improves crystallinity, hydrophilicity and reduces nonradiative associated defects. The mechanical properties of zirconia films examined using static and dynamic nanoindentation demonstrate that hardness increases from 7.60 ± 0.26 GPa to 11.08 ± 0.90 GPa and elastic modulus increases from 170.74 ± 4.98 GPa to 210.13 ± 5.56 GPa when annealing temperature increases. The post-annealing temperature influences provide a method for tuning the optical, wetting and mechanical characteristics of zirconia thin film.

Investigation of Thermodynamic Properties of Zirconia Thin Films by Statistical Moment Method

The moment method in statistical (SMM) dynamics is used to study the thermodynamic quantities of ZrO2 thin films taking into account the anharmonicity effects of the lattice vibrations. The average lattice constant, thermal expansion coefficient and specific heats at the constant volume of ZrO2 thin films are calculated as a function of temperature, pressure and thickness of thin film. SMM calculations are performed using the Buckingham potential for the ZrO2 thin films. In the present study, the influence of temperature, pressure and the size on the thermodynamic quantities of ZrO2 thin film have been studied using three different interatomic potentials. We discuss temperature and thickness dependences of some thermodynamic quantities of ZrO2 thin films and we compare our calculated results with those of the experimental results.

Structural and Optical Properties of Zirconia Thin Films

Zirconium oxide (ZrO2) is very interesting material because of its outstanding mechanical, optical and biological properties. In this research we have prepared zirconia thin films by sol gel technique. Five different samples were prepared by varying molarities of starting sol (0.25, 0.050, 0.075, 0.1 and 0.125M). XRD patterns demonstrate the presence of mixed tetragonal zirconia (t-ZrO2) and monoclinic zirconia (m-ZrO2) phases. An increase in tetragonal content has been observed at higher molarities of sol. Crystallite size of zirconia thin films increases with increase in molarity of sol. Optical spectrum shows that thin film has relatively high value of transmission up to 70%.

Structural and optical properties of zirconia thin films deposited by reactive high-power impulse magnetron sputtering

Zirconia films are deposited by reactive high power impulse magnetron sputtering (HiPIMS) technology on glass and indium-tin-oxide (ITO)/glass substrates. Preparation, microstructure and optical characteristics of the films have been studied. During deposition, the influence of the target power and duty cycle on the peak current–voltage and power density has been observed in oxide mode. Transparent thin films under different oxygen proportions are obtained on the two substrates. Atomic force microscopy measurements showed that the surface roughness of the films was lower by reactive HiPIMS than DC sputtering for all oxygen contents. The transmission and reflectance properties of differently grown zirconia films were also investigated using an ultraviolet–visible spectrophotometer. The optical transmittance of films grown on glass substrates by HiPIMS reached maximum values above 90%, which exceeded that by DC sputtering. The band edge near 5.86eV shifted to a lower wavelength for zirconia films prepared with oxygen flow rates lower than 4.5sccm. For the films prepared on ITO/glass substrates, the transmittance and the band gap of zirconia films were limited by ITO films; a maximum average transmittance of 84% was obtained at 4.5sccm O2 and the energy band gap was in the range of 3.7–3.8eV for oxygen flow rates ranging from 3.5 to 5.0sccm. Finally, the electrical properties of zirconia films have also been discussed.

Effect of sol concentration on the structural, morphological, optical and photoluminescence properties of zirconia thin films

ZrO2 thin films were deposited on quartz substrates from 10wt.%, 20wt.% and 40wt.% solutions of Zirconium-n-butoxide in isopropanol by sol–gel dip-coating technique. Higher concentrated sols of 20wt.% and 40wt.% exhibited faster gelation, where as 10wt.% sol remained stable for two months and films synthesized from this sol remained transparent and continuous even for 12 coatings. Ellipsometric study revealed that refractive index of the films increased with increase in sol concentration which is ascribed to the decrease in porosity. X-ray diffraction study showed that a tailoring of grain size from 7.9 to 39.2nm is possible with increase in sol concentration. Atomic force microscopy studies showed a change in growth mode from vertical to lateral mode with increase in sol concentration. The film surface revealed positive skewness and high kurtosis values which make them favorable for tribological applications. The average optical transmittance in the visible region is highest (greater than 90%) for the film deposited from 10wt.% sol. The optical band gap decreased from 5.74 to 5.62eV with increase in the sol concentration. Photoluminescence (PL) spectra of the films exhibit an increase in the emission intensity with increase in sol concentration which substantiates better crystalline quality of the film deposited from 40wt.% sol and increase in oxygen vacancies. The “Red shift” of the PL spectra with increase in sol concentration originates from the increase in the grain size with sol concentration which makes it suitable for generation of solid state lighting in light emitting diode.

Electrical and structural properties of zirconia thin films prepared by reactive magnetron sputtering

Thin films of ZrO 2 were prepared by reactive magnetron sputtering. Annealing of the films exhibited a drastic change in the properties due to improved crystallinity and packing density. The root mean square roughness of the sample observed from atomic force microscope is about 5.75 nm which is comparable to the average grain size of the thin film which is about 6 nm obtained from X-ray diffraction. The film annealed at 873 K exhibits an optical band gap of around 4.83 eV and shows +4 oxidation state of zirconium indicating fully oxidized zirconium, whereas higher annealing temperatures lead to oxygen deficiency in the films and this is reflected in their properties. A discontinuity in the imaginary part of the AC conductivity was observed in the frequency range of tens of thousands of Hz, where as, the real part does not show such behavior.

Properties of zirconia thin films prepared by reactive magnetron sputtering

The search for alternative dielectric materials with high dielectric constant, thermodynamic stable on silicon substrate and low direct tunneling current leads to oxide based materials like zirconia. Zirconia thin films were prepared by reactive magnetron sputtering. The capacitance voltage, ac and dc electrical characteristics were investigated and the values like fixed oxide charges were calculated and compared among the samples with and without annealing. Films annealed at 700 °C showed a dielectric constant ∼ 26 with interface trap densities of 1.629 × 10 12 eV − 1 cm − 2 .

Surface morphology and properties of zirconia thin films prepared at different deposition rates

ZrO2 thin films were prepared on BK7 glass substrates by electron beam evaporation deposition method. The influence of deposition rate varying from 1·2 to 6·3 nm s−1 on surface morphology and other properties of ZrO2 films were examined. With increasing deposition rate, the surface defect density increased. The decrease in half width at full maximum in X-ray diffraction pattern with deposition rate indicates an increase in crystal dimension with increasing deposition rate. Electron beam deposited ZrO2 films are known to be inhomogeneous. From the change of the peak transmittance value, it can be deduced that the inhomogeneity of ZrO2 films strengthened gradually with increasing deposition rate. The type of surface defects changed from nodules to craters when the deposition rate was high enough.

Mechanical Properties of Zirconia Thin Films Deposited by Filtered Cathodic Vacuum Arc

Surface Young's modulus (E), hardness (H), and yield strength (Y) of zirconia films deposited on Si substrate by filtered cathodic vacuum arc (FCVA) under different oxygen flow rate were studied by nano‐indentation measurement and finite element modeling. Identified by X‐ray diffraction, the structure of the films evolves from amorphous to monoclinic, and then to amorphous, with oxygen flow rate increasing from 10 to 80 standard cubic centimeters per minute, which affects the mechanical properties of the films. It is found that the elastic–perfect‐plastic constitutive model is successfully applied to the films with amorphous structure; however inadequate for the monoclinic ZrO2, indicating that dislocation‐related plasticity possibly occurs during nano‐indentation.

Synthesis and properties of zirconia thin films

Thin films of zirconia have been synthesized using reactive DC magnetron sputtering. It has been found that films with good optical constants, high refractive index (1·9 at 600 nm) and low extinction coefficient can be prepared at ambient temperatures. The optical constants and band gap and hence the composition are dependent on the deposition parameters such as target power, rate of deposition and oxygen background pressure. Thermal annealing of the films revealed that the films showed optical and crystalline inhomogeneity and also large variations in optical constants.

A comparative study of the optical properties of zirconia thin films prepared by ion-assisted deposition

Thin films of zirconia have been prepared using ion-assisted deposition over a wide range of ion energies from 0 to 700 eV and their optical properties such as refractive index and absorption investigated. The ions were produced using two different ion sources: (1) a Heitmann-type low energy source; (2) a Kaufman-type broad beam ion source to produce ions in the energy range 100–700 eV. It was observed that the refractive index value increased with increasing ion energy. However, the extinction coefficient showed lower values at lower energies than at higher energies. A bulk-like value of 2.2 for the refractive index at a wavelength of 650 nm has been obtained at 500eV energy. The absorption at this energy is fairly high (0.008), but films with negligible absorption have been obtained at lower energies.

Structural and optical properties of zirconia thin films

Thin films of zirconia have been deposited using reactive electron beam evaporation in neutral and ionized oxygen media. The variation in optical properties and structure with post-deposition annealing temperature in the range 300–850 °C has been studied. It has been found that the refractive index decreases and the extinction coefficient increases with increasing annealing temperature. Phase transitions have been characterized using IR absorption in conjunction with X-ray diffraction. The effect of ambient background ions on optical properties is not as marked as that on structure.