The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Klaus Prume - One of the best experts on this subject based on the ideXlab platform.
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Effects of the top-Electrode Size on the piezoelectric properties (d33 and S) of lead zirconate titanate thin films
Journal of Applied Physics, 2004Co-Authors: P. Gerber, C. Kugeler, Ulrich Böttger, Rainer Waser, Andreas Roelofs, Klaus PrumeAbstract:The effects of a decreasing top Electrode Size on the electric and piezoelectric properties of tetragonal Pb(ZrX,Ti1−X)O3 thin films are investigated. The effective piezoelectric small-signal coefficient d33,eff and the piezoelectric large signal-strain S are measured using a double-beam laser interferometer. Both properties are found to decrease rapidly with decreasing Size of the used Pt top Electrode for the investigated dimensions of 5mmto100μm edge length (square pads). While the loss of d33,eff is as high as 75%, the influence on the relative permittivity is only small. The source of the pad Size effect on the measured piezoelectric properties is found to be the mechanics of the layered structure commonly used for piezoelectric measurements (Pt∕PZT∕Pt∕TiO∕SiO2∕Si), [PZT,Pb(Zrx,Ti1−x)O3] which is verified by finite element simulations.
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Simulation and measurements of the piezoelectric properties response (d/sub 33/) of piezoelectric layered thin film structures influenced by the top-Electrode Size
14th IEEE International Symposium on Applications of Ferroelectrics 2004. ISAF-04. 2004, 1Co-Authors: Klaus Prume, P. Gerber, C. Kugeler, A. Roelofs, Ulrich Böttger, Rainer Waser, Thorsten Schmitz-kempen, S. TiedkeAbstract:The properties of piezoelectric thin film layered structures are in the focus of many investigations. Significant decreasing piezoelectric properties have been observed with decreasing top-Electrode Size. These results are obtained by measurements of the effective piezoelectric small-signal coefficient d/sub 33,eff/ and the piezoelectric large signal-strain S using a double-beam laser interferometer. Samples are investigated with squared top-Electrodes with dimensions of 0.1 mm to 1 mm edge length. The loss of d/sub 33,eff/ is as high as 50 %, whereas the influence on the relative permittivity is only small. This work investigates this behaviour by calculating the influence of varying elastic and geometrical properties of substrate, Electrodes, and piezoelectric thin film on the effective piezoelectric small-signal coefficient d/sub 33,eff/ by means of finite element simulations. Beside the clamping effect of the substrate under electrical operating conditions also the influence of thermally induced mechanical stresses after cooling from 4000/spl deg/C to room temperature is calculated. From measurements and simulations it can be concluded that the source of the pad Size effect on the measured piezoelectric properties can he attributed to the mechanics of the layered structure.
Walter Paulus - One of the best experts on this subject based on the ideXlab platform.
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shaping the effects of transcranial direct current stimulation of the human motor cortex
Journal of Neurophysiology, 2007Co-Authors: Michael A Nitsche, S Doemkes, T Karakose, David Liebetanz, Frithjof Tergau, Andrea Antal, Nicolas Lang, Walter PaulusAbstract:Transcranial DC stimulation (tDCS) induces stimulation polarity-dependent neuroplastic excitability shifts in the human brain. Because it accomplishes long-lasting effects and its application is simple, it is used increasingly. However, one drawback is its low focality, caused by 1) the large stimulation Electrode and 2) the functionally effective reference Electrode, which is also situated on the scalp. We aimed to increase the focality of tDCS, which might improve the interpretation of the functional effects of stimulation because it will restrict its effects to more clearly defined cortical areas. Moreover, it will avoid unwanted reversed effects of tDCS under the reference Electrode, which is of special importance in clinical settings, when a homogeneous shift of cortical excitability is needed. Because current density (current strength/Electrode Size) determines the efficacy of tDCS, increased focality should be accomplished by 1) reducing stimulation Electrode Size, but keeping current density constant; or 2) increasing reference Electrode Size under constant current strength. We tested these hypotheses for motor cortex tDCS. The results show that reducing the Size of the motor cortex DC-stimulation Electrode focalized the respective tDCS-induced excitability changes. Increasing the Size of the frontopolar reference Electrode rendered stimulation over this cortex functionally inefficient, but did not compromise the tDCS-generated motor cortical excitability shifts. Thus tDCS-generated modulations of cortical excitability can be focused by reducing the Size of the stimulation Electrode and by increasing the Size of the reference Electrode. For future applications of tDCS, such paradigms may help to achieve more selective tDCS effects.
S. Tiedke - One of the best experts on this subject based on the ideXlab platform.
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Electrode Size dependence of piezoelectric response of lead zirconate titanate thin films measured by double beam laser interferometry
Applied Physics Letters, 2013Co-Authors: S. Sivaramakrishnan, Thorsten Schmitz-kempen, P. Mardilovich, Ashley D. Mason, Andreas Roelofs, S. TiedkeAbstract:The Electrode Size dependence of the effective large signal piezoelectric response coefficient (d33,f) of lead zirconate titanate (PZT) thin films is investigated by using double beam laser interferometer measurements and finite element modeling. The experimentally observed Electrode Size dependence is shown to arise from a contribution from the substrate. The intrinsic PZT contribution to d33,f is independent of Electrode Size and is equal to the theoretical value derived assuming a rigid substrate. The substrate contribution is strongly dependent on the relative Size of the Electrode with respect to the substrate thickness. For Electrode Sizes larger than the substrate thickness, the substrate contribution is positive and for Electrode Sizes smaller than the substrate thickness, the substrate contribution is negative. In the case of silicon substrates, if the Electrode Size is equal to the substrate thickness, the substrate contribution vanishes, and the measured value of d33,f is equal to the theoretical value under the rigid substrate assumption.
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Simulation and measurements of the piezoelectric properties response (d/sub 33/) of piezoelectric layered thin film structures influenced by the top-Electrode Size
14th IEEE International Symposium on Applications of Ferroelectrics 2004. ISAF-04. 2004, 1Co-Authors: Klaus Prume, P. Gerber, C. Kugeler, A. Roelofs, Ulrich Böttger, Rainer Waser, Thorsten Schmitz-kempen, S. TiedkeAbstract:The properties of piezoelectric thin film layered structures are in the focus of many investigations. Significant decreasing piezoelectric properties have been observed with decreasing top-Electrode Size. These results are obtained by measurements of the effective piezoelectric small-signal coefficient d/sub 33,eff/ and the piezoelectric large signal-strain S using a double-beam laser interferometer. Samples are investigated with squared top-Electrodes with dimensions of 0.1 mm to 1 mm edge length. The loss of d/sub 33,eff/ is as high as 50 %, whereas the influence on the relative permittivity is only small. This work investigates this behaviour by calculating the influence of varying elastic and geometrical properties of substrate, Electrodes, and piezoelectric thin film on the effective piezoelectric small-signal coefficient d/sub 33,eff/ by means of finite element simulations. Beside the clamping effect of the substrate under electrical operating conditions also the influence of thermally induced mechanical stresses after cooling from 4000/spl deg/C to room temperature is calculated. From measurements and simulations it can be concluded that the source of the pad Size effect on the measured piezoelectric properties can he attributed to the mechanics of the layered structure.
Andreas Roelofs - One of the best experts on this subject based on the ideXlab platform.
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Electrode Size dependence of piezoelectric response of lead zirconate titanate thin films measured by double beam laser interferometry
Applied Physics Letters, 2013Co-Authors: S. Sivaramakrishnan, Thorsten Schmitz-kempen, P. Mardilovich, Ashley D. Mason, Andreas Roelofs, S. TiedkeAbstract:The Electrode Size dependence of the effective large signal piezoelectric response coefficient (d33,f) of lead zirconate titanate (PZT) thin films is investigated by using double beam laser interferometer measurements and finite element modeling. The experimentally observed Electrode Size dependence is shown to arise from a contribution from the substrate. The intrinsic PZT contribution to d33,f is independent of Electrode Size and is equal to the theoretical value derived assuming a rigid substrate. The substrate contribution is strongly dependent on the relative Size of the Electrode with respect to the substrate thickness. For Electrode Sizes larger than the substrate thickness, the substrate contribution is positive and for Electrode Sizes smaller than the substrate thickness, the substrate contribution is negative. In the case of silicon substrates, if the Electrode Size is equal to the substrate thickness, the substrate contribution vanishes, and the measured value of d33,f is equal to the theoretical value under the rigid substrate assumption.
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Effects of the top-Electrode Size on the piezoelectric properties (d33 and S) of lead zirconate titanate thin films
Journal of Applied Physics, 2004Co-Authors: P. Gerber, C. Kugeler, Ulrich Böttger, Rainer Waser, Andreas Roelofs, Klaus PrumeAbstract:The effects of a decreasing top Electrode Size on the electric and piezoelectric properties of tetragonal Pb(ZrX,Ti1−X)O3 thin films are investigated. The effective piezoelectric small-signal coefficient d33,eff and the piezoelectric large signal-strain S are measured using a double-beam laser interferometer. Both properties are found to decrease rapidly with decreasing Size of the used Pt top Electrode for the investigated dimensions of 5mmto100μm edge length (square pads). While the loss of d33,eff is as high as 75%, the influence on the relative permittivity is only small. The source of the pad Size effect on the measured piezoelectric properties is found to be the mechanics of the layered structure commonly used for piezoelectric measurements (Pt∕PZT∕Pt∕TiO∕SiO2∕Si), [PZT,Pb(Zrx,Ti1−x)O3] which is verified by finite element simulations.
Henning Heuer - One of the best experts on this subject based on the ideXlab platform.
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Optimization of Electrode Size for aluminum-nitride matrix ultrasonic transducers in the frequency range above 200 MHz.
Ultrasonics, 2012Co-Authors: Yangjie Wei, Thomas Herzog, Henning HeuerAbstract:This paper describes an optimization method of the top Electrode Size for a thin film matrix ultrasonic transducer (M-UT) in the frequency range above 200 MHz. The goal of this work is to design an optimal top Electrode Size for an M-UT providing the maximal output peak-peak voltage (V(PP)) and the maximal signal-to-noise ratio (SNR) without additional electrical impedance matching. In order to reduce the complexity of the M-UT with more than 1000 elements, an intrinsic matching by Electrode Size variation is necessary. However, the Size of a single element top Electrode for an M-UT is related to the number of elements within a targeted sensor area, V(PP) and SNR of the transducer. In this paper, varying the active area of the top Electrode from 0.09 to 25 mm(2) shows that for an Al-AlN-Al on silicon wafer configuration connected with a JSR Ultrasonics pulser/receiver (50 ohms), the optimal Electrode Size is 1 mm(2). With the optimal Size Electrode, the maximum output V(PP) of 0.08 V and the SNR of 42.93 dB are achieved at the resonance frequency of 225 MHz, and the bandwidth is 16.21 MHz.
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Investigation on Electrode Size of high frequency ultrasonic transducers
2012Co-Authors: Yangjie Wei, Thomas Herzog, Henning HeuerAbstract:This paper presents a concept to increase the performance of high frequency ultrasonic transducers. For a sandwich high frequency ultrasonic transducer, the top Electrode should be smaller than the piezoelectric plate to avoid shortcuts and edge effects. However, its Size can influence properties of the transducer, and until now there is no research about it published. A theoretical investigation about influence of the top Electrode Size on properties of a transducer is conducted in this paper. First, two factors related with the top Electrode Size based on transmission coefficient and stored energy are proposed; Then, analysis on an Al-AlNAl on silicon wafers with different Electrode Sizes are performed and the results prove the effectiveness and the validity of the proposed factors. Finally, electrical impedance matching experiments are conducted to improve the properties of transducers with different Electrode Sizes, and the experiment results show that the improved resolution and sensitivity after matching.