A-site acceptor doped LaNbO4 thin film formation and structural investigation

In this paper, doped La1-xAxNbO4 (A = Ca, Mg) thin films were formed using electron beam vapor deposition. The influence of the doping concentration of A site dopants (A = Ca, Mg) on the thin ceramics surface microstructure, morphology and electrical properties, including the charge carrier mobility and diffusion coefficient, was studied. It was found that the formed thin films are dense (>96 %) and have homogenous nanocrystalline structure composed of the tetragonal LaNbO4 phase. The total conductivity of the formed thin films is in 10-3 S/cm range for Ca-doped LaNbO4 and 10-4 S/cm range for Mg-doped LaNbO4 at 800 °C under wet H2 reducing atmosphere. The nature of protonic conduction was confirmed by the isotopic effect. The calculated ΔHmob,H is 57 kJ/mol at 650 °C for the La0.995Ca0.005NbO4 film, which total conductivity was highest in the present study (9.52∙10-3 S/cm at 800 °C under wet H2 reducing atmosphere). ΔHmob,H increases steadily with increasing the dopants’ concentration from 57 kJ/mol to 84 kJ/mol. The charge mobility decreases from 2.32×10-5 cm2/V∙s to 6.25×10-7 cm2/V∙s as the dopants’ concentration increases at 650 °C

Dynamics of the formation of thin LaNbO4 films using magnetron sputtering

Doped lanthanum niobate thin films were deposited using magnetron sputtering technique. W and Mg cathodes were used for doping LaNbO4 thin films. Thin films were deposited on two types of substrates: amorphous optical quartz (SiO2) and polycrystalline Alloy 600 (Ni-Cr-Fe). The structural and morphological analysis was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), atomic force microscope (AFM). The nonequilibrum growth of the thin films and the nonlinear dynamics of the sputtered atoms and their oxides is observed. XRD analysis revealed that Mg promotes crystallite formation in La1-xMgxNbO4 thin films and W inhibits crystallite formation in LaNb1-xWxO4 thin films. EDS analysis showed that La1-xMgxNbO4 and LaNb1-xWxO4 thin films are nonstoichiometric. They have deficit or excess oxygen and Nb (compared to lanthanum). It was noticed that the nonstoichiometry has influence on the morphology of thin films. The cross section of formed thin films analysis showed that grains or fibers are not visible in the thin films with excess oxygen concentration and thin films with deficit of oxygen has fiber type structure. Oxygen concentration also influences the surface morphology. The roughness of the surface increases (0.2 nm ÷ 0.3 nm for La1-xMgxNbO4 and 0.2nm ÷ 0.8 nm for LaNb1-xWxO4) with decreasing oxygen concentration

Dynamics of electrical charge carriers in Mg-doped TiO2 thin films under reducing conditions

Mg-doped TiO2 thin ceramic films prepared using e-beam deposition were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction (XRD), and impedance spectrometer. The influence of the concentration of Mg dopant and systematic investigation of the dynamics of electronic charge carriers’ transport in the thin films are provided. The dopants concentration affected structural properties and nonlinear behaviour of electrical conductivity of the thin films. XRD analysis revealed anatase structure of TiO2 thin films with the decrease of cristallinity by increasing the concentration of Mg dopant. Total conductivity and activation energy depend on Mg concentration and the ambient temperature. The highest total conductivities 6.17E-6 S/cm and 5.50E-4 S/cm were achieved using 1.2 mol % (873 K) and 2.5 mol % (1230 K) dopant concentrations respectively. The highest relaxation frequencies and shortest relaxation times of 4.92E-02 s at 833 K and 3.48E-05 s at 1230 K temperature are obtained for the same experimental points, whereas the longest relaxation times 3.18E-01 s at 833 K and 1.21E-04 s at 1230 K temperature were estimated for 8 mol % Mg-doped TiO2 films

Influence of the Initial Powder’s Specific Surface Area on the Properties of Sm-Doped Ceria Thin Films

The influence of a specific surface area of evaporating powder on the properties of thin Sm-doped cerium (SDC) oxide films has not yet been sufficiently investigated. Therefore, SDC films were deposited by e-beam evaporation using Sm0.2Ce0.8O2-δ powders of 6.2 m2/g, 11.3 m2/g, and 201.3 m2/g specific surface area on SiO2, and Al2O3 substrates. X-Ray Diffraction (XRD) analysis showed that SDC thin films deposited on 600 °C SiO2 substrates changed their preferred orientation from (111) to (311), (200), and (220) when evaporating 6.2 m2/g and 11.3 m2/g powders and using 0.2 nm/s, 1.2 nm/s, and 1.6 nm/s deposition rates. However, thin films deposited by evaporating powder of 201.3 m2/g specific surface area do not change their preferred orientation. The crystallite size of the SDC thin films depends on the substrate temperature and specific surface area of the evaporating powder. It increases from 6.40 nm to 89.1 nm with increasing substrate temperature (50⁻600 °C). Moreover, crystallites formed by evaporating a powder of 201.3 m2/g specific surface area are 1.4 times larger than crystallites formed by evaporating a powder of 6.2 m2/g specific surface area. An impedance analysis revealed that the normalized resistance of “grains„ is higher than the normalized resistance of grain boundaries. Moreover, a total conductivity depends on crystallite size. It changes from 4.4 × 10−7 S/cm to 1.1 × 10−2 S/cm (600 °C) when the crystallite sizes vary from 6.40 nm to 89.10 nm. In addition, the optical band gap becomes wider with increasing crystallite size proving that the Ce3+ concentration decreases with an increasing crystallite size

Structural and Electrochemical Properties of Scandia Alumina Stabilized Zirconia Thin Films

This work presents a systematic investigation of scandia alumina stabilized zirconia (ScAlSZ, composition: ZrO2:Sc2O3:Al2O3 93:6:1 wt.%) thin films (~2 μm). Thin films were formed by the e-beam evaporation method on 450 °C substrates. The influence of Al concentration on thin film microstructure, structure, and electrochemical properties was characterized by EDS, XRD, Raman, and EIS methods. It was found that the aluminum concentration in the deposited thin films decreased with an increase in the deposition rate. The concentration of Al changed from 15.9 to 3.8 at.% when the deposition rates were 0.2 and 1.6 nm/s, respectively. The crystallinity of the thin films depended strongly on the concentration of Al, resulting in an amorphous phase when Al concentration was 22.2 at.% and a crystalline phase when Al concentration was lower. ScAlSZ thin films containing 15.9 at.% of Al had monoclinic and tetragonal phases, while thin films with 1.6 and 3.8 at.% of Al had a mixture of cubic, tetragonal, and monoclinic phases. The phase transition was observed during the thermal annealing process. Cubic and rhombohedral phases formed in addition to monoclinic and tetragonal phases appeared after annealing ScAlSZ thin films containing 15.9 and 22.2 at.% of aluminum. The highest total ionic conductivity (σbulk = 2.89 Sm−1 at 800 °C) was achieved for ScAlSZ thin films containing 3.8 at.% of Al. However, thin films containing a higher concentration of aluminum had more than 10 times lower total conductivity and demonstrated changes in activation energy at high temperatures (>560 °C). Activation energies changed from ~1.10 to ~1.85 eV

Structure and Photocatalytic Activity of Copper and Carbon-Doped Metallic Zn Phase-Rich ZnO Oxide Films

ZnO is one of the most important industrial metal oxide semiconductors. However, in order to fully realise its potential, the electronic structure of ZnO has to be modified to better fit the needs of specific fields. Recent studies demonstrated that reactive magnetron sputtering under Zn-rich conditions promotes the formation of intrinsic ZnO defects and allows the deposition of metallic Zn phase-rich ZnO films. In photocatalytic efficiency tests these films were superior to traditional ZnO oxide, therefore, the purposeful formation of intrinsic ZnO defects, namely Zn interstitials and oxygen vacancies, can be considered as advantageous self-doping. Considering that such self-doped ZnO remains a semiconductor, the natural question is if it is possible to further improve its properties by adding extrinsic dopants. Accordingly, in the current study, the metallic Zn phase-rich ZnO oxide film formation process (reactive magnetron sputtering) was supplemented by simultaneous sputtering of copper or carbon. Effects of the selected dopants on the structure of self-doped ZnO were investigated by X-ray diffractometer, scanning electron microscope, X-ray photoelectron spectroscope and photoluminescence techniques. Meanwhile, its effect on photocatalytic activity was estimated by visible light activated bleaching of Methylene Blue. It was observed that both dopants modify the microstructure of the films, but only carbon has a positive effect on photocatalytic efficiency

Properties on Yttrium-Doped/Undoped Barium Cerate and Barium Zirconate Thin Films Formed by E-Beam Vapor Deposition

As electrolyte materials for proton conductive fuel cells, perovskite-type materials such as barium cerates and barium zirconates have received a lot of attention due to their high protonic conduction at intermediate temperatures. Yet, the crystalline structure and the microstructure of the electrolyte layers are of the utmost importance that define the resulting protonic conductivity. The aim of this research was to investigate the formation of doped/undoped BCO and BZO thin films using e-beam vapor deposition and to analyze the influence of the formation parameters on the microstructural and crystallographic properties. Crystalline structure and microstructure were investigated by X-ray diffractometer and scanning electron microscope, while the elemental composition of the resulting thin films was analyzed by an energy-dispersive X-ray spectroscope. It was found that the formed thin films were highly dense and consisted of the oriented columnar grains. The crystallinity of the thin films was strongly expressed with the predominant crystallographic orientations for undoped/doped barium cerates. Yttrium dopant had an influence on the lattice parameters and crystallite sizes. With the chosen technological parameters allowed to both, barium cerates and barium zirconates did not form carbonates and did not experience the degradation process

Properties on Yttrium-Doped/Undoped Barium Cerate and Barium Zirconate Thin Films Formed by E-Beam Vapor Deposition

As electrolyte materials for proton conductive fuel cells, perovskite-type materials such as barium cerates and barium zirconates have received a lot of attention due to their high protonic conduction at intermediate temperatures. Yet, the crystalline structure and the microstructure of the electrolyte layers are of the utmost importance that define the resulting protonic conductivity. The aim of this research was to investigate the formation of doped/undoped BCO and BZO thin films using e-beam vapor deposition and to analyze the influence of the formation parameters on the microstructural and crystallographic properties. Crystalline structure and microstructure were investigated by X-ray diffractometer and scanning electron microscope, while the elemental composition of the resulting thin films was analyzed by an energy-dispersive X-ray spectroscope. It was found that the formed thin films were highly dense and consisted of the oriented columnar grains. The crystallinity of the thin films was strongly expressed with the predominant crystallographic orientations for undoped/doped barium cerates. Yttrium dopant had an influence on the lattice parameters and crystallite sizes. With the chosen technological parameters allowed to both, barium cerates and barium zirconates did not form carbonates and did not experience the degradation process

Properties of Barium Cerate-Zirconate Thin Films

In this work, we review several experimental results showing the electrical properties of barium cerate-zirconate thin films and discuss them in view of the possible influence of various factors on their properties. Most of the presented Ba(Ce, Zr, Y)O3 thin films were formed by the pulsed laser deposition (PLD) technique, however thin films prepared using other methods, like RF magnetron sputtering, electron-beam deposition, powder aerosol deposition (PAD), atomic layer deposition (ALD) and spray deposition are also reported. The electrical properties of the thin films strongly depend on the film microstructure. The influence of the interface layers, space-charge layers, and strain-modified layers on the total conductivity is also essential but in many cases is weaker