Piezoelectric Component in 2-2 magnetoelectric sensors

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Magnetoelectric (ME) composites composed of a magnetostrictive and a piezoelectric phase are promising for uncooled unshielded magnetic field sensors for medical applications. The amplitude of the magneto electric effect and the signal-to-noise ratio (SNR) depend, among others, as a product property on the piezoelectric properties and the electrode configuration. In this project measures are to be evaluated and exploited in order to further increase the amplitude of the magneto electric effect and the signal-to-noise ratio by variation of the piezoelectric component. As a consequence the limit of detection of the magneto electric magnetic field sensors should be further lowered. In doing so three partial aspects will be examined in close collaboration of modelling (Gerken) and experiments (Quandt). In the first area ME thin-film sensors utilizing interdigital electrodes will be studied. By employing interdigital electrodes for the thin-film sensors, higher signal strengths can be achieved. At the same time, due to lower capacitance, an increase in the noise level is observed. Here systematic experimental studies of the influence of design variations (max. electrode spacing, electrode layout, film thickness, substrate thickness) and electrical parameters (poling, capacitance, noise components) are to be carried out and a detailed model of the SNR developed. In the second area the usage of BCZT-films will be explored. Along with the important aspect of legally required lead avoidance, these films may show a further effect increase with respect to PZT-films. For this a large-area film deposition either by chemical solution deposition (CSD) or by magnetron sputtering on wafer level, has to be established. The necessary conditions for such a large-area deposition will be explored. As these lead-free ferroelectrics will be employed in combination with interdigital electrodes, oxidic and insulating seed layers for BCZT-films need to be found. A comparison of these films will be performed with PZT-films which also employ interdigital electrodes and with already developed, low-loss AlN-films in plate capacitor configuration. As third area the usage of multiple piezoelectric components in one sensor is to be investigated. By separation of the effect of magnetically induced straining, a reduction of cross-sensitivities due to acoustic signals and vibrations is anticipated. As for the magneto electric composites of this project, either standard magnetostrictives (e.g. FeCoSiB-films) or novel, property enhanced, multilayer films of project P2 are used. The results obtained in this project will enter the projects P4, P9 and P10.