Gunnar Suchaneck

Gunnar Suchaneck
Technische Universität Dresden | TUD · Institute of Solid-State Electronics

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219
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Publications

Publications (219)
Article
Full-text available
This work presents an examination and unification of fragmented data on spin polarization in half-metallic, ferrimagnetic oxides. It also includes well understood ferromagnetic metals for comparison. The temperature and disorder dependencies of the spin polarization are evaluated. Both the temperature dependence of the tunnel magnetoresistance and,...
Article
Full-text available
Работа посвящена формированию поверхностных структур на монокристаллах ниобата лития. Прове-дено исследование топографии его поверхности после распыления пучком газовых кластерных ионов. Закономерности возникновения на поверхности волнообразного рельефа (рипплов) проанализированы с использованием подхода, основанного на функции спектральной плотнос...
Article
The low‐field magnetoresistance properties in double‐perovskite strontium ferromolybdate core–shell structures arise from spin‐dependent tunneling through a barrier formed by the shell. It is strongly dependent on synthesis conditions. In this work, first, the resistivity behavior of granular strontium ferromolybdate ceramics comprising intergrain...
Article
Full-text available
Thin-film strontium ferromolybdate is a promising material for applications in room-temperature magnetic tunnel junction devices. These are spin-based, low-power-consuming alternatives to CMOS in non-volatile memories, comparators, analog-to-digital converters, and magnetic sensors. In this work, we consider the main tasks to be solved when creatin...
Article
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Antiphase boundaries in strontium ferromolybdate induce antiferromagnetically coupled spins of the Fe ions at the boundary affecting both the magnetic properties and the electron transport across the boundary. In this work, we present a first 3-D presentation of the antiphase boundary in strontium ferromolybdate. For the first time we estimate the...
Article
Full-text available
Magnetization is a key property of magnetic materials. Nevertheless, a satisfactory, analytical description of the temperature dependence of magnetization in double perovskites such as strontium ferromolybdate is still missing. In this work, we develop, for the very first time, a model of the magnetization of nanosized, magnetically inhomogeneous S...
Article
In this work, we develop a model for the description of the low-field magnetoresistance of Sr2FeMoO6−δ ceramics, for the first time considering the magnetic field dependence of the tunneling barrier height. The core of the model is the temperature and magnetic field dependence of the reduced magnetization m. Spin polarization is considered as a fun...
Article
Full-text available
In this work, we develop for the first time a model for the description of magnetoresistance in nanosized, granular Sr2FeMoO6‐δ‐SrMoO4 core‐shell structures which is based on fluctuation induced tunneling model. Parameters of the fluctuation induced tunneling model of granular materials are calculated. The magnetic field is considered to affect the...
Article
This work is a contribution to the understanding of the electrical resistivity in strontium ferromolybdate (Sr2FeMoO6-δ, SFMO) ceramics. It demonstrates that an appropriate thermal treatment leads to the formation of dielectric SrMoO4 shells at the surface of SFMO nanograins. In samples without SrMoO4 shells, the sign of the temperature coefficient...
Chapter
Currently, many publications report on the electrocaloric effect and its application for cooling devices. This work focusses now on the prospects of using ceramic thin films in electrocaloric cooling. We introduce the electrocaloric effect and examine electrical properties, mechanical boundary conditions as well as the film microstructure affecting...
Article
Materials properties affecting EC device operation are discussed based on an analytically tractable model of a layered EC refrigerator. Special attention was paid to thermal and interface thermal resistances. Estimates of the average cooling power of a stacked MEMS-based EC refrigerator were made.
Preprint
Full-text available
This work is a contribution to the understanding of the electrical resistivity in strontium ferromolybdate (SFMO) ceramics. It demonstrates that an appropriate thermal treatment leads to the formation of dielectric SrMoO4 shells at the surface of SFMO nanograins. In samples without SrMoO4 shells, the sign of the temperature coefficient of resistanc...
Article
In this work, a model based on the existence of polarized nanoregions (PNRs) in a dielectric matrix is presented for a quantitative analysis of the hysteresis behavior in relaxor ferroelectrics. The PNRs are simulated by spheroids covered with a thin dielectric envelope. The electric field dependence of the polarization is described by the Landau-G...
Article
Full-text available
Strontium ferromolybdate double perovskite is a promising candidate for room-temperature spintronic applications. Nevertheless, SFMO has not yet found wide application in spintronics. This is attributed to the low reproducibility of its magnetic properties which partially originates from their strong dependence on the ordering degree of Fe and Mo i...
Article
Full-text available
This work reviews some fundamental issues which are relevant for the fabrication of stable phase strontium ferromolybdate thin films. The main challenges for strontium ferromolybdate thin film deposition arise from the sensitivity of the material's magnetic properties to point defect formation: (i) Antisite defect formation and oxygen nonstoichiome...
Article
Full-text available
The dopant and pyroelectric coefficient depth profiles of LiNbO 3 single crystals grown by Czochralski method were investigated. Doping was performed after crystal growth by thermal diffusion at elevated temperatures. Diffusion doping did not deteriorate the pyroelectric properties of the crystal. ARTICLE HISTORY
Article
Full-text available
Spatial changes of optical and pyroelectric properties of doped LiNbO 3 single crystals were investigated. Doping with Cu and Fe was performed after crystal growth by thermal diffusion at elevated temperatures. The crystals were all-side-covered by corresponding metal oxide powder before annealing. In order to reveal the role of various types of di...
Article
In lightweight construction, structural components with integrated piezoelectric sensors and actuators find application for condition monitoring, structural health monitoring, vibrational control, and reduction of noise emission. In order to create such multifunctional, so-called smart components, an integration technique for serial production, des...
Article
Integrated piezoceramics enable smart structures which interact with their environment. Their polarization state can be probed by thermal methods based on the pyroelectric effect. In this work, single PZT plates and PZT plates embedded into low temperature co‐fired ceramics (LTCC) are heated by thermal pulses and the pyroelectric current is measure...
Article
Full-text available
Materials properties affecting EC device operation are discussed based on an analytically tractable model of a layered EC refrigerator. Special attention was paid to thermal and interface thermal resistances. Estimates of the average cooling power of a stacked MEMS-based EC refrigerator were made.
Article
Full-text available
LiNbO3 thin films with a thickness of 200 nm were deposited onto Al2O3 substrate by RF-magnetron sputtering technique without intentional substrate heating. The results demonstrate that post-growth infrared pulsed light annealing of the amorphous LiNbO3 films leads to the formation of two phases, LiNbO3 and LiNb3O8. After annealing at temperatures...
Article
Until now, relaxor ferroelectrics are considered as a class of disordered materials possessing peculiar structures and properties which are not yet generalized into a universal model explaining the significant amount of experimental data available. In this work, we demonstrate that one feature of relaxor ferroelectrics - the extraordinary dielectri...
Article
Hysteresis phenomena of relaxor ferroelectrics have been modeled by considering spheroidal polar nanoregions covered by a thin shell of a linear dielectric both embedded into a ferroelectric matrix. The electric field within the spheroid is described by the Landau–Ginzburg–Devonshire equation. The resulting phase transition temperature is strongly...
Article
In this work, we consider the impact of the P-E hysteresis on the performance of electrocaloric cooling using the phenomenological theory of ferroelectrics. For reasons of simplicity, we use approximations of sufficiently small electric fields and polarization. A large electrocaloric effect was obtained for a slim P-E hysteresis (small remnant pola...
Article
In this work, we attribute the ferroelectric-relaxor crossover in BaTiO3-based solid solution to the percolation of the BO6 octahedra occupied by solute atoms. BaTiO3-based solid solutions which are favorable for electrocaloric applications possess then a composition in the vicinity of the ferroelectric-relaxor crossover. For the first time, we con...
Article
Zusammenfassung In Leichtbaustrukturen wird der Polarisationszustand von integrierten Piezokeramiken mittels thermischer Anregung zerstörungsfrei geprüft. Wärmeschwingungen (Laser-Intensitäts-Modulations-Methode) oder Wärmeimpulse führen zu einem pyroelektrischen Strom im Frequenz- bzw. Zeitbereich. Das Frequenzspektrum wird analytisch mit Hilfe th...
Article
In this work, we consider electrocaloric (EC) device operation at high electric fields E above the temperature Tm of the maximum dielectric permittivity. Here, the EC response is determined by the temperature dependence of dielectric permittivity while dielectric losses are comparably low. We discuss materials selection and EC device concepts. An u...
Article
Full-text available
In this work, we apply the thermal wave method and the thermal pulse method for non-destructive evaluation of the polarization state of piezoelectric transducers. The pyroelectric response of the transducer is analyzed after heating it by a modulated laser beam or laser pulses. We demonstrate that the Fourier transform of the pulse response of a pi...
Article
Full-text available
In this work, we apply the thermal-pulse method to evaluate the polarization state of piezoelectric transducers. The pyroelectric current is measured in time domain and Fourier-transformed. The results are compared to frequency spectra determined by the laser intensity modulation method.
Article
In this work, we determine the dielectric functions of multi-target, reactively sputtered BaZr0·2Ti0.8O3 by spectroscopic ellipsometry in the photon energy range from 0.8 to 8.7 eV. Based on this data, we discuss the interband transition energies and the spectral dependencies of the refractive index and the absorption coefficient.
Conference Paper
Relaxor ferroelectrics are promsing in EC cooling devices due to a new upper bound of the electrocaloric (EC) effect combined with a corresponding novel figure of merit of EC materials performance. In general, the performance of EC coolers is limited either by the thermal time constants of heat switches or by the heat transfer coefficient to the ga...
Conference Paper
In this work, we present analytical and finite element method (FEM) modeling to describe the time dependence of the pyroelectric current of embedded piezoelectrics generated by a laser pulse. Analytical solutions of the one-dimensional heat transfer equation consider a two-layer model, account for the experimentally derived heat pulse shape and the...
Article
Full-text available
This paper reports on the deposition of AlN and AlXSc1−XN films by pulse magnetron sputtering. The first part will focus on the AlXSc1−XN deposition process in comparison to the already established AlN process. The effect of doping AlN with Sc regarding piezoelectric and mechanical properties is presented. The films show the expected increase of pi...
Article
Full-text available
In this work, we apply the thermal wave method and the thermal pulse method for non-destructive characterisation of the polarisation state of embedded piezoelectric transducers. Heating the sample with a square-wave modulated laser beam or a single laser pulse leads to a pyroelectric current recorded in the frequency or time domain, respectively. I...
Article
In this work, we consider the electrocaloric effect in relaxor ferroelectrics above the temperature of the dielectric constant maximum. For the purpose of modelling, a modified Curie--Weiss law was adapted to approximate the complex physics of relaxors. The requirements to electrocaloric materials derived on this basis are fulfilled by relaxor sing...
Article
Full-text available
Electrocaloric (EC) materials provide a solid-state cooling technology without polluting liquid refrigerants and noisy mechanical parts. Currently, basic research in this field is mainly focused on materials with a first-order phase transition exhibiting a large polarization change in a narrow temperature region near the phase transition point (Cur...
Article
Large area film deposition was performed by means of multitarget reactive magnetron sputtering from metallic targets (Pb, Ti, Zr) with a diameter of 200 mm onto Cu-coated Kapton® HN substrates. High-power pulse sputtering has been employed for the Zr-target (or alternatively for the Ti-target). Film composition profiles were evaluated by XPS and RB...
Conference Paper
This paper reports on the deposition of AlN and AlXSc1-XN films by pulse magnetron sputtering. The influence of process parameters on the film properties and the evaluation of the films for micro energy harvesting are presented. For AlN it is shown, that film stress can be varied in a considerable range between compressive and tensile stress while...
Article
Structural components with integrated piezoceramic sensors and actuators manufactured by high pressure die casting were studied using the thermal wave method. Thermal waves were created by irradiating the surface with an intensity modulated laser beam, and the pyroelectric current was monitored in dependence on modulation frequency. Laser modulatio...
Conference Paper
In this work, lead magnesium niobate-lead titanate (1−x)Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 ((1−x)PMN-xPT) thin films with PT-fractions of 6.5 to 20% were fabricated on Pt(111)-coated Si wafers by multi-target reactive sputtering using four metallic targets (Pb, Mg, Nb, Ti). In order to increase the dielectric strength, co-doping with Mn was performed...
Conference Paper
In this work, the thermal wave method was applied to characterize PZT disks and embedded PZT plates with regard to the polarization magnitude and spatial homogeneity. The samples were exposed to periodic heating by means of a laser beam and the pyroelectric response was determined. Thermal relaxation times (single time constants or distributions of...
Conference Paper
In this work, lead magnesium niobate-lead titanate (1-x)Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 (PMN-PT) thin films with PT-fractions of 6.5 to 20% were fabricated on Pt(111)-coated Si wafers for the first time by multitarget reactive sputtering using four metallic targets (Pb, Mg, Nb, Ti).
Article
Full-text available
In this work, we have investigated the surface topography evolution of sol-gel deposited SiO2-SnO2 nanocomposite films annealed in the temperature range 200–600°C. The fractal dimension of atomic force microscopy images of the films was determined by the cube counting method and the triangulation method. The fractal dimension was shown to be an app...
Article
Full-text available
In this work, we evaluate the hierarchical surface topography of reactively sputtered nanocrystalline Pb(Zr,Ti)O 3 and TiO 2 thin films as well as plasma-treated antireflective PET films by means of determining the fractal dimension and power spectral density (PSD) of surface topography recorded by atomic force microscopy (AFM). Local fractal dimen...
Conference Paper
In this work, we evaluate the pyroelectric response of PZT plates and rods embedded in epoxy resin, low temperature cofired ceramics and polyamide by measuring the pyroelectric current spectrum originated by temperature oscillations generated by illuminating the sample surface with a square-wave-modulated laser beam. Transfer functions H(iω) descri...
Conference Paper
In this work, we evaluate the electric field dependence of the electrocaloric effect in BaTiO3-based materials. Figures of merits are proposed which are applicable to electrocaloric devices.
Conference Paper
In this work, the polarization state of piezofiber composites consisting of lead zirconate titanate (PZT) fibers embedded in epoxy resin was evaluated by means of thermal wave methods. The average pyroelectric coefficient was found to be one order of magnitude less than that of PZT ceramic plates. The pyroelectric current spectrum was recorded duri...
Conference Paper
In this work, we demonstrate that the thermal wave method is a promising approach for non-destructive evaluation of polarization state of embedded piezoelectrics in integrated sensor–actuator modules. The embedded piezoceramics are subjected to periodic heating by a square wave-modulated laser array through the top layers. A transient thermal analy...
Conference Paper
The formation mechanisms of paramagnetic centers originating from Zr3+ and Cr5+ ions and the influence of the nanoparticle composition on thermal generation processes of these paramagnetic centers were studied in ZrO2 structure by electron paramagnetic resonance. A set of nanosized zirconium oxide powders (nominally pure ZrO2, ZrO2 doped with corre...
Article
In this work, we investigate the polarization state of a Low-Temperature-Cofired-Ceramics (LTCC)/PZT sensor-actuator and a Macro-Fiber Composite (MFC) actuator. An analytical solution for a 1-D thermal problem was derived for an embedded piezoelectric plate. Transient thermal analysis of the more complicated MFC actuator was performed using finite...
Article
Full-text available
We describe the fabrication of lead zirconate titanate (PZT) nanodisc arrays isolated by a polymer layer and contacted with a top electrode. PZT thin films were deposited by multitarget sputtering onto a platinum/titanium bottom electrode and structured by means of nanosphere lithography. To guarantee short-circuit-free deposition of a top electrod...
Article
Full-text available
In this work, we investigate nanosized Fe-ZnO thin films, deposited on glass substrates by sol-gel method and dip-coating technique. The precursor sol is prepared by dissolving of Zn(CH3COO)2.2H2O and Fe(NO3)3.9H2O in 2-methoxyethanol with addition of monoethanolamine as surfactant. The Fe content in the ZnO thin films is selected to be 0.25, 0.5 a...
Article
In this work we evaluate the polarization state of PZT plates and rods embedded into low temperature co-fired ceramics, polymers and epoxy resin by measuring the pyroelectric current spectrum as a result of temperature oscillations generated by illuminating the sample surface with a square-wave-modulated laser beam. Changes in pyroelectric current...
Article
In this work, we analyze the requirement to (Ba,Ca)(Zr,Ti)O3 thin films for applications in electrocaloric devices. We demonstrate that large temperature changes are realized mostly independent of the used material by applying sufficient electric fields. Ferroelectrics exhibiting a diffuse phase transition are beneficial for electrocaloric applicat...
Article
In this work, Pb(Zr,Ti)O-3 thin films were used to fabricate well-ordered nanodot arrays by means of nanosphere lithography. This technique is based on a two-step etch process that enables excellent control of the fabrication of ordered nanodisc arrays of defined height, diameter, and pitch. Piezoresponse force microscopy was used to investigate bo...
Article
In this work, Pb(Zr,Ti)O3 thin films were used to fabricate well-ordered nanodot arrays by means of nanosphere lithography. This technique is based on a two-step etch process that enables excellent control of the fabrication of ordered nanodisc arrays of defined height, diameter, and pitch. Piezoresponse force microscopy was used to investigate bot...
Article
This work demonstrates the benefit of the thermal wave method for the evaluation of the polarization state of embedded piezoelectrics. Two types of samples were investigated: A low-temperature co-fired ceramics (LTCC)/lead zirconate titanate (PZT) sensor-actuator and a macro-fiber composite (MFC) actuator. At modulation frequencies below 10 Hz, the...
Conference Paper
Full-text available
In this work, we investigate the hierarchical surface topography of solid oxide fuel cell electrolytes consisting of zirconia stabilized with 10% Sc2O3 and 1% CeO2 (1Ce10ScSZ) synthesized at 1300–1400 °C and anodes of 60 wt% 1Ce10ScSZ and 40 wt% NiO synthesized at 1250 to 1550 °C. The fractal dimension of AFM images of the films was determined by t...
Conference Paper
Formation mechanisms of paramagnetic centers originating from Zr3+ and Cr3+ ions as well as the influence of composition of nanoparticles on thermogeneration processes of these paramagnetic centers in ZrO2 structure were studied. A set of nanosized powders of zirconium oxide was investigated by electron paramagnetic resonance method: nominally pure...
Conference Paper
In this work, we describe the fabrication of PZT nanodisc arrays isolated by a polymer layer and contacted with a top electrode. PZT thin films were deposited by multi-target sputtering onto a platinum/titanium bottom electrode and structured by means of nanosphere lithography. To guarantee short-circuit-free evaporation of a top electrode, the spa...
Conference Paper
In this work, we investigate the composition profile of nanocrystalline Pb(Zr, Ti)O3 (PZT) thin films deposited by means of reactive magnetron sputtering from 200 mm diameter metallic targets (Pb, Ti, Zr). High-power pulse sputtering has been employed for alternatively the Zr- or Ti-target. Composition analysis and profiling was performed by means...
Conference Paper
Full-text available
In this work, we investigate the hierarchical surface topography evolution of sol-gel deposited SiO 2 -SnO 2 nanocomposite films annealed in the temperature range of 200 to 600°C, reactive sputtered TiO 2 and Pb(Zr,Ti)O 3 nanocrystalline thin films and plasma-treated antireflective PET films by means of determining the fractal dimension and power s...
Article
Full-text available
Nanocomposite SiO2-SnO2 thin films were prepared on oxidized silicon substrates using the sol-gel technique with SnCl2·2H2O as a tin precursor and tetraethylorthosilicate (TEOS) as a silica source. The porous structure of the films was investigated by atomic force microscope. Gas sensitivity of the samples was measured at different temperatures and...
Article
Full-text available
Using the sol-gel technique, nanocomposite SiO2-SnO2 thin films comprising a designed hierarchical pore structure were prepared on cost-efficient oxidized silicon substrates. These films exhibit advanced gas sensing properties both for reducing gases and oxygen due to an efficient analyte transport by mesoporores.
Article
In this work, we investigate microstructure and composition of nanocrystalline lead-titanium-zirconium oxide thin films reactively sputtered directly on copper-coated polymer films without intentionally substrate heating. Film microstructure characterization was carried out by scanning probe microscopy. Surface topography was described by fractal d...