František Kundracik

Characterization of yttria-stabilized zirconia thin films deposited by electron beam evaporation on silicon substrates

Structure, phase composition and electrical conductivity of thin yttria-stabilized zirconia (YSZ) films deposited by electron beam evaporation on a silicon (1 0 0) substrate at different temperatures i.e. room temperature (r.t.), 700 and 830°C, as well as the quality of the YSZ–Si interface have been investigated. The phase composition was verified by Raman spectroscopy and by infrared (i.r.) transmission measurements. The structure of films changed in agreement with their electrical conductivity depending on the deposition temperature. Both structure and thereby electrical conductivity were influenced by the high concentration of Y2O3 stabilizer used and by the post-deposition thermal treatment of films. The deposition temperature was also important in determining the quality of the YSZ–Si interface and hence the accessible sweep of the surface potential. The capacitance–voltage characteristics of the metal–insulator–semiconductor (MIS) structures incorporating YSZ films measured at r.t. showed hysteresis and positive shifts of the flat-band voltages.

Correlation between microscopic and macroscopic properties of yttria stabilized zirconia: 1. Single crystals

Abstract This paper reports on the results of the research on the yttria-stabilized zirconia single crystals and on the defects obtained in the wide range of yttria amounts, 1.13 x

Structure and electrical conductivity of multicomponent metal oxides having scheelite structure

The investigated bismuth vanadate, BiVO4, bismuth vanadomolybdate, Bi0.85V0.55Mo0.45O4, and pure bismuth molybdate, Bi2Mo3O12, oxides prepared by novel spray drying technique having the scheelite structure were found to be monoclinic in the case of BiVO4 and Bi2Mo3O12, whereas Bi0.85V0.55Mo0.45O4 is body-centered tetragonal. The distribution of intergranular porosity across polycrystalline samples is inhomogeneous, being larger parallel to the flat compression of the powder samples. The high polarizability of Bi3+ cations with their lone-pair electrons influences stability of the disordered oxygen sublattice. All as-prepared systems undergo a slight structural change of the oxygen arrangement during the sample heating in the temperature region of 340–390°C, probably due to an order ⇆ disorder transition, resulting in a decrease of lattice oxygen ion mobility and decrease of electrical conductivity. The total bulk electrical conductivity of both vanadate systems is essentially ionic at low temperatures and high oxygen partial pressures. Diffusion of the lattice oxygen ions in the Bi1−x/3V1−xMoxO4 scheelite structure is indirectly related to the introduction of cation vacancies. The highest conductivity was observed in the multicomponent oxide Bi0.85V0.55Mo0.45O4, both as-prepared and thermally treated. Above 350°C the conductivity of BiVO4 and partially also Bi0.85V0.55Mo0.45O4 oxides is affected by the n-type electron contribution.

A microcontroller-based system for automated and continuous sky glow measurements with the use of digital single-lens reflex cameras

In recent years, the scientific community has shown an increased interest in sky glow research. This has revealed an increased need for automated technology that enables continuous evaluation of sky glow. As a result, a reliable low-cost platform has been developed and constructed for automating sky glow measurement. The core of the system is embedded software and hardware managed by a microcontroller with ARM architecture. A monolithic photodiode transimpedance amplifier is used to allow linear light measurement. Data from the diode are collected and used to arrange the exposure time of every image captured by the digital single-lens reflex camera. This proposal supports experimenters by providing a low-cost system to analyse sky glow variations overnight without a human interface.

Structural and electrical properties of double-layer ceria/yttria stabilized zirconia deposited on silicon substrate

Abstract Analyses of the phase composition and electrical characterization of double-layer CeO 2 /YSZ and single-layer CeO 2 , YSZ dielectrics grown on a Si (100) substrate at 200°C by electron beam evaporation as well as of the quality of interfaces between the oxide layers and silicon substrates were performed. The structure of all investigated oxide layers was found to be of the fcc fluorite type. The electrical conductivity of the investigated oxide layers and the average grain size change due to the post-deposition thermal treatment. The temperature dependence of the activation energy of the electrical conductivity is associated with different impurity phases in the oxide layers. Due to the lowest density of defects assessed from deep-level-transient-spectroscopy (DLTS) measurements, the CeO 2 /Si interface seems to be an optimum compared to the other oxide layer configurations. The dielectric constants e r (YSZ)=18.3 and e r (CeO 2 )=3.4 were estimated from the accumulation capacitances of the C – V curves.

Generalization of electromagnetic scattering by charged grains through incorporation of interband and intraband effects.

Scattering of electromagnetic radiation by electrically charged spherical particles is treated theoretically. A generalization of the approach is performed by incorporating both intraband and interband effects, while a new oscillatory term corresponding to the classical dispersion theory and the semi-quantum approach is considered. It is shown through a set of numerical experiments that interband effects may reduce the amplitude of resonant peaks for scattering, Q(sca), and absorption, Q(abs), and cause a shift of peak positions to longer wavelengths. In general, the resonant features due to interband and intraband effects can occur at different frequencies; thus, both together may result in qualitatively and quantitatively new optical signatures of electrically charged particles. This is a motivating factor for experimentalists who can use the particles as targeted probes, for example, in mapping the electric fields in different media based on scattering and/or absorption properties of electrified particulate systems.

Effect of crystallographic structure on electrical and mechanical characteristics of Sm2O3-Doped CeO2 films

Electrical conductivity, dielectric permittivity and mechanical hardness of the polycrystalline CeO2 + xSm2O3 (x = 0, 10.9–15.9 mol %) films prepared by Electron Beam Physical Vapour Deposition (EB-PVD) and Ionic Beam Assisted Deposition, (IBAD), techniques were investigated in dependence on their structure and microstructure influenced by the deposition conditions, namely composition, deposition temperature and Ar+ ion bombardment. The electrical conductivity of doped ceria prepared without Ar+ ion bombardment and investigated by the impedance spectroscopy, IS, was found to be predominantly ionic one under the oxidizing atmosphere/low-temperature conditions and the higher amounts of Sm2O3 (>10 mol %) used. The bulk conductivity as a part of total measured conductivity was a subject of interest because the grain boundary conductivity was found to be ∼3 orders of magnitude lower than the corresponding bulk conductivity. Ar+ ion bombardment acted as a reducer (Ce4+ → Ce3+) resulting in the development of electronic conductivity. Dielectric permittivity determined from the bulk parallel capacitance measured at room temperature and the frequency of 1 MHz, similarly as the mechanical hardness measured by indentation (classical Vickers and Depth Sensing Indentation-DSI) techniques were also found to be dependent on the deposition conditions. The approximative value of hardness for the investigated films deposited on the substrate was estimated using a simple phenomenological model described by the power function HV = HV0 + aPb and compared with the so-called apparent hardness (substrate + investigated film) determined by the classical Vickers formula. Results obtained are analyzed and discussed.

Effect of composition changes on properties and defect structure of crystalline Sm-doped ZrO2

Polymorphous structure, electrical conductivity, absorption coefficient, refractive index, and mechanical characteristics of crystalline system ZrO2 + x Sm2O3 (x = 4–43 mol %) is investigated. Vickers microhardness is investigated by the well-known quasi-static indentation method. Plastic microhardness and the effective elastic modulus are studied by the depth-sensing indentation technique. Special attention is devoted to the ordered defect fluorite structure, pyrochlore phase Sm2Zr2O7, observed for x = 43 mol %. Potential applications of the investigated system are discussed.

Thin Film Electrolytes: Yttria Stabilized Zirconia and Ceria

Data obtained in an investigation of yttria-stabilized zirconia (YSZ) and ceria thin films are reviewed and discussed with special regard to the preparation conditions, namely, the temperature of deposition and the post-deposition thermal treatment of films. The structure, phase composition, electrical and dielecric properties, and problems that can be met when measuring effective and real ohmic resistances are compared with the results reported by other authors. The YSZ (CeO2)/Si interfaces are studied by means of deep level transient spectroscopy and feedback charge method capacitance–voltage measurements.

Estimation of Garstang emission function parameters from skyglow monitoring by all-sky camera

A knowledge of an emission function of gound-based light sources is crucial for skyglow modelling. In the case of complex light sources as cities, it is in practice impossible to specify accurately their emission characteristics. Therefore various semi-empirical functions determined by some suitably defined parameters are usually used for description of city light emissions. Assessment of these parameters is obviously extremely difficult. Whether for the complexity of inverse problems of radiative transfer, or for the lack of specialized measurement devices. The aim of the article is to present a simple and effective method of retrieval of city emission function parameters from easily available experimental data. The method is applied on the Garstang emission function because of its generally wide spread utilisation in the light pollution research area. However, it can be in principle applied also on another suitably parametrized emission functions of ground-besed sources. We start from a theoretical model of diffuse radiation intensity distribution over the clear sky, which is based on the successive order of scattering method and which allows relatively simple inverse retrieval of the Garstang parameters. Ratios of zenith radiance to horizontal irradiance at various distances from a source serve as the experimental input data. Such data can be obtained by obvious inexpensive devices what forms the main advantage of the introduced method. In the paper we present utilisation of all-sky cameras which allow simultaneous measurement of the both demanded quantities.