New Concepts for Functional 0-3 Nanocomposites and Magnetic Field Sensors
Modern applications of functional granular (0-3) nanocomposites require a precise tailoring of the composite morphology, filling factor, electrical properties and chemical composition. In Part I of this work a versatile deposition concept for the tailoring of 0-3 nanocomposites is elaborated and a respective deposition system is constructed. Ceramic-based 0-3 nanocomposites with embedded metallic magnetic particles are chosen to demonstrate the feasibility of the deposition concept. Aiming at functional 0-3 nanocomposites for high-k and magnetoelectric (ME) materials, aluminum nitride (AlN) is chosen as the matrix and cobalt (Co) for the particulate phase. Suitable deposition processes for the individual composite constituents are developed and the resulting piezoelectric AlN films and magnetic Co nanoparticles are characterized. Finally, 0-3 AlN/Co nanocomposites are produced and investigated regarding their suitability for high-k and ME applications. An increase of by up to a factor of 30 indicates the potential of the concept for the PVD preparation of high-k materials. Regarding the design of high-performance ME materials, several inherent challenges of the 0-3 nanocomposite approach with metallic particles are identified and existing literature is critically reviewed. The ME investigation is conducted within the framework of the SFB 855 “Magnetoelectric Composites - Future Biomagnetic Interfaces” which aims at the development of highly sensitive ME sensors especially for biomagnetic applications. The SFB not only focuses on the design of suitable ME materials, but also on the development of new sensor concepts. Accordingly, in Part II a novel sensor concept based on MEMS technology and the delta-E effect is presented. The demonstrator consists of a tipless AFM microcantilever with a resonance frequency of approximately 300 kHz which is excited mechanically. The resonator’s eigenfrequency can be shifted by an external magnetic field as the amorphous (Fe90Co10)12Si12B10 functional coating exhibits the delta-E effect. The demonstrator is shown to detect magnetic fields as low as 400 nT at biomagnetically relevant frequencies. It furthermore requires no cooling, possesses vector-field capability and is potentially fully integrable. Prospective optimized sensors based on the proposed concept are estimated to detect fields of 100 pT or below, rendering them relevant for medical applications like advanced drug delivery or in-vivo imaging.