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Publications (47)
Energy harvesters offer an attractive power source alternative in particular for the next generation of mobile sensor applications. The current work investigates the power output of bulk micromachined 3 mm x 2 mm x 50 μm sized cantilever-type piezoelectric (2 μm AlScN) energy harvesting device that is magnetically driven by miniaturized NdFeB perma...
Ferroelectric lead-free thin films of the composition (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCZT) were deposited by pulsed laser deposition on Pt/TiO2/SiO2/Si substrates using a ceramic BCZT target prepared by a conventional solid state reaction. The target material itself shows a piezoelectric coefficient of d33 = 640 pm/V. The (111) textured thin films p...
We show the use of nickel-titanium (NiTi) metal thin films as functional substrates of magnetoelectric composites allowing the composites' mechanical resonance to be tuned towards the frequency range of interest by employing the gradual change of the Young's modulus during the martensite-austenite phase transformation. Such composites are successfu...
Measurements of the converse magnetoelectric effect, observed for mesoscopic cantilever type magnetoelectric composites, are presented. The silicon based samples employ 2 µm of amorphous (Fe90Co10)78Si12B10 film as soft magnetic, magnetostrictive phase. The piezoelectric phase consists of 2 µm sputter deposited, highly textured aluminum nitride (Al...
Thin-film magnetoelectric sensors are able to measure very low magnetic fields. As a consequence the hypothesis that magnetoelectric sensors could be used for biomagnetic measurements was often mentioned but never proven. In this contribution the first proof of this hypothesis will be given by the measurement of the (well-known) R-wave of the human...
Neuartige, auf dem magnetoelektrischen Effekt basierende Sensoren haben das Potential, biomagnetische Signale messen zu können. Allerdings koppeln aufgrund ihrer Struktur auch akustische Störungen mit in den Sensor ein, die das gesuchte magnetische Nutzsignal uberlagern. Abhilfe schafft eine Kompensation der Störung mit Hilfe akustischer Referenzse...
Thin-film magnetoelectric sensors, i.e. composites of magnetostrictive and piezoelectric materials, are able to measure very low magnetic flux densities in the picotesla range. In order to further improve the limit of detection it is of high importance to understand and quantify the relevant noise sources. In this paper a common model for the defle...
Composite magnetoelectrics implemented as thin film heterostructures are discussed in view of
their applicability as highly sensitive magnetic field sensors. Here, either PZT or AlN served as
piezoelectric component. The magnetostrictive phase consisted of layer systems based on FeCo or
(Fe 90 Co 10 ) 78 Si 12 B 10 . All functional layers were depo...
Thin-film magnetoelectric (ME) sensors offer a promising potential to measure biomagnetic signals in the near future. Unfortunately, this sensor type shows usually a large cross-sensitivity to all kinds of mechanic distortion due to the resonant structure. In order to overcome this problem several sensor designs have been proposed. Beside these app...
Prior investigations on magnetoelectric (ME) thin film sensors using amorphous FeCoSiB as a magnetostrictive layer and AlN as a piezoelectric layer revealed a limit of detection (LOD) in the range of a few pT/Hz1/2 in the mechanical resonance. These sensors are comprised of a Si/SiO2/Pt/AlN/FeCoSiB layer stack, as dictated by the temperatures requi...
A low-temperature sputter deposition process for the synthesis of aluminum nitride (AlN) thin films that is attractive for applications with a limited temperature budget is presented. Influence of the reactive gas concentration, plasma treatment of the nucleation surface and film thickness on the microstructural, piezoelectric and dielectric proper...
Magnetoelectric thin film composites have demonstrated their potential to detect sub-pT magnetic fields if mechanical resonances (typically few hundred Hz to a few kHz) are utilized. At low frequencies (1–100 Hz), magnetic field-induced frequency conversion has enabled wideband measurements with resonance-enhanced sensitivities by using the nonline...
In the present work, magnetoelectric-piezotronic devices have been fabricated using exceptionally long (mm long) ZnO nano- and microneedles grown by the simple and versatile flame transport synthesis approach. The piezotronic response to an applied magnetic field has been investigated for state of the art magnetoelectric (ME) sensors containing AlN...
Recent advances in magnetoelectric sensor systems prove their growing importance for biomagnetic sensing applications. But with increasing sensitivity down to some pT in mechanical resonance the sensors require techniques to convert low frequent biomagnetic signals in the range of 0.1 Hz to 40 Hz into the mechanical resonance frequency of the canti...
For magnetic field measurements with magnetoelectric sensors sensitivities for AC magnetic fields in the femto-Tesla range are desired. Important factors for the necessary signal/noise ratio are extrinsic noise sources such as vibrations and acoustics. In this paper a concept to reduce the noise contributions from these sources is suggested and inv...
Magnetische Maßstäbe in Verbindung mit Magnetfeldsensoren sind Stand der Technik in der Positionssensorik. In dem Verbundprojekt AQUILA wird diese Technologie weiterentwickelt mit dem Ziel, eine höhere Auflösung zu erreichen. Diese soll unter 100 nm liegen. Um dieses Ziel zu erreichen, werden neue Konzepte für Maßstäbe und die passenden dazugehörig...
Sensors based on the magnetoelectric (ME) effect have the potential to be genuine alternatives for measuring bio-magnetic signals. Unfortunately, the sensor structure usually inhibits the problem that several non-magnetic types of noise couple mechanically into the sensor: in this contribution, we will focus on undesired acoustic coupling. Therefor...
The local magnetization behavior of the magnetostrictive phase of ferromagnetic/piezoelectric magnetoelectric composites is compared to the hysteretic response using advanced magneto-optical imaging. Local magnetoelastic relaxation leads to the formation of magnetization modulated branched domain structures in the magnetic phase. This results in a...
A polymer-based magnetoelectric 2-2 composite was fabricated in a thin film approach by direct spin coating of polyvinylidenefluoride-co-trifluoroethylene onto a Metglas substrate without the usage of an adhesive for the mechanical coupling between the piezoelectric and magnetostrictive materials. For a prototype single-sided clamped cantilever, a...
Magnetoelectric (ME) thin film composites on silicon cantilevers are fabricated using Pb(Zr0.52Ti0.45)O3 (PZT) films with interdigital transducer electrodes on the top side and FeCoSiB amorphous magnetostrictive thin films on the backside. These composites without any direct interface between the piezoelectric and magnetostrictive phase are superio...
Highly sensitive AC magnetic field sensors are presented using magnetoelectric composites consisting of magnetostrictive and piezoelectric phases. They are offering passive nature, high sensitivity, large effect enhancement at mechanical resonance, and large linear dynamic range. Thin‐film magnetoelectric 2‐2 composites benefit from perfect couplin...
Si cantilevers with thin film ME 2-2 composites consisting of AlN as the piezoelectric phase and of amorphous magnetostrictive Metglas as the magnetostrictive phase show an extremely high ME coefficient of up to 1800 V/cmOe at mechanical resonance and about 3 V/cmOe out of resonance at a magnetic bias field of 6 Oe. Using an exchanged biased multil...
Ferroelectric lead-free thin films of 0.5(Ba0.7Ca0.3TiO3) - 0.5[Ba(Zr0.2Ti0.8)O-3] (BCZT) were successfully deposited by pulsed laser deposition on Pt/TiO2/SiO2/Si substrates using a ceramic BCZT target prepared by conventional solid state reaction. The in (1 1 1) direction orientated 600 nm thick films shows a clamped piezoelectric response of app...
The corrosion behaviour of bulk and thin film specimens consisting of commercial magnesium alloys AZ31 and AZ80 was investigated by electrochemical tests in 3.5wt.% NaCl solution and in phosphate buffered saline solution (PBS) at room temperature. Corrosion tests indicated that the corrosion rates are nearly equal, but localized attack was more pro...
Thin films of TiO2-Pt nanocomposites containing 4 at% Pt have been processed via spin-coating. Film characterization involved XRD, Raman as well as XPS and scanning surface potential microscopy (SSPM). After annealing at 500 °C the thin films consisted of nanocrystalline anatase and a few nm Pt nanoclusters. Annealing at 600 °C resulted in the form...
A hybrid sol–gel-powder method was used to process 3–6 μm thick lead zirconate titanate films via spin-coating a Ni-base alloy and silicon substrates. The films were crack free and possessed a fine microstructure. High effective piezoelectric coefficients, d33, of 250 pm/V were obtained from piezoelectric hysteresis loops using a laser vibrometer....
3 μm thick lead zirconate titanate films were processed via a hybrid sol-gel-powder method on Inconel substrates for pressure sensor applications. Microstructure, ferroelectric, dielectric and piezoelectric properties are reported. It is shown that crack- free films with good high remnant polarization, and high effective piezoelectric coefficient,...
The pyroelectric and piezoelectric properties of thick PZT films processed via a new sol–gel method are being investigated. The films were deposited on gold-coated alumina substrates. The pyroelectric properties are being evaluated using pyrodynamic measurements with either a laser or thermoelectric heat source. The pyroelectric coefficient is obta...
The ferroelectric and piezoelectric properties of lead zirconate titanate thin films deposited on a (La-0.8,Sr-0.2)MnO3 (LSMO)/Ti-metal foil heterostructure are reported. The results are compared to those of films of similar thickness deposited on platinized silicon substrate. It is shown that the films deposited on LSMO/Ti are characterized by squ...
The ferroelectric and piezoelectric properties of lead zirconate titanate thin films deposited on a (La0.8,Sr0.2)MnO3 (LSMO)/Ti-metal foil heterostructure are reported. The results are compared to those of films of similar thickness deposited on platinized silicon substrate. It is shown that the films deposited on LSMO/Ti are characterized by squar...
Pb(Zr,Ti)O3 (PZT) thin films were deposited on different substrate heterostructures including platinized silicon, stainless steel and Ni-based alloy foils. A buffer layer of (La0.8Sr0.2)MnO3 (LSMO) between PZT and substrate was used. The pyroelectric coefficients were determined using low frequency sinusoidal temperature waves. It is demonstrated t...
Thin films of erbium doped lead zirconate titanate (PZT) of different thickness were deposited by sol–gel technique on Pt/TiO2/SiO2/Si substrates. Capacitance–voltage measurements show that the dielectric constant continuously increases with the thickness. This is interpreted in terms of effects due to a low permittivity interfacial layer in series...
Er doped PbTiO3 (PET) thin films were prepared via modified sol-gel method on (111)Pt/Ti/SiO2/Si substrates. SEM and XRD investigations showed completely crystallized fine grained perovskite structure achieved after annealing at 700degreesC for 5 min. Lattice tetragonal distortion (c/a) was found to decrease from 1.044 for pure PT to 1.036 for PET...
A hybrid sol-gel-powder method for the low-cost processing of thick PZT films is presented. Thick films with a thickness in the range from 2.5 to 10 μm can be processed using few processing steps. The films are spin-coated on a platinized Si substrate and annealed at temperatures up to 800°C. Microstructure is characterized by means of scanning ele...
Pyroelectric Pb1,1(Zr0.58Fe0.2Nb0.2Ti0.02)O3/Pb1.1(Zr0.9Ti0.1)O3 (PZFNT/PZT) bimorph thin films are processed via a modified sol-gel method on highly textured (1 1 1)Pt/Ti/SiO2/Si substrates. XRD and SEM investigations show full pyrochlore to perovskite phase transformation after annealing at 750 C. XPS depth profiling reveals diffusion of Fe leadi...
Nb doped PZT films with Nb concentrations of 0, 5, 8 and 12 mol% are being processed via chemical solution deposition on platinized Silicon substrates. An original processing route including seed layer and additional PbO coating is presented whereby homogeneous, pyrochlore free microstructures with 111/100 texture are obtained. The temperature depe...
High quality ferroelectric thin films with the stoichiometry Pb1.1(Zr0.58Fe0.2Nb0.2Ti0.02)O3 (PZFNT) have been processed via chemical solution deposition on textured (111) Pt/Ti/SiO2/Si substrates. X-ray diffractometry and scanning electron microscopy investigations show that full transformation from pyrochlore to perovskite phase is accomplished a...
La3+ doped PZT thin films of a Pb1.025La0.05(Zr0.48, Ti0.52)O3 nominal stoichiometry have been processed via chemical solution deposition on (111)-Pt/TiO2/SiO2/Si-(100). The crystallization textures and crystallization kinetics have been investigated in the temperature range from 550 to 700°C, starting from a common annealed condition at 500°C. The...
The crystallization kinetics of strongly textured (100)-PZT thin films on highly textured (111)-Pt have been investigated in the temperature range from 550 to 700°C. It is shown that the crystallization proceeds by the formation of globular, Zr-depleted, and Pb-rich particles that show necklace patterns. The crystallization kinetics can be describe...
Nb5+ doped PZT thin films of a nominal stoichiometry of Pb1.1(Zr0.47, Ti0.47, Nb0.05)O3 have been processed via metallorganic deposition on (111)-Pt/TiO2/SiO2/Si. The crystallization textures and crystallization kinetics have been investigated in the temperature range from 550 to 700 °C, starting from a common pre-firing condition at 500 °C. The di...
PLZT {lanthanum doped PZT [Pb(Zr0.52, Ti0.48)O3]} thin films with 5, 8 and 10 mol% lanthanum were processed via chemical solution deposition on (111)-Pt/TiO2/SiO2/Si (100) and LaNiO3 (LNO)/(111)-Pt/TiO2/SiO2/Si (100). The thin films were investigated in terms of the influence of lanthanum content and substrate heterolayer structure on the microstru...
Ceramic nanofiltration membranes were produced by using a polymeric sol gel route. The prepared membranes are made of ZrO2 and TiO2 and have a thickness of < 50 nm. The medium pore size is in the range of < 2 nm. The cut-off valve of < 1.000 D was determined by filtration tests with two colouring agents.
