Nanocharacterization of materials for biomagnetic sensing using TEM

摘要: The collaborative research center (SFB 855" Magnetoelectric Composites-Future Biomagnetic Interfaces") aims to develop biomagnetic sensors with the capability of a precise detection of signals in the Femtotesla regime. Novel ME composites are the material of choice and include strain mediated 2-2, 0-3, and 1-1 designs. Such composites are accompanied in many instances with complex structural features. As functionality and property optimization of the materials are based on the minute understanding of such phenomena, structural characterization becomes indispensable particularly at the nanoscale. Within the scope of this work methods of transmission electron microscopy (TEM) were applied to obtain detailed information of the real structure from SFB relevant (magnetostrictive and piezoelectric) materials and ME composites provided by other cooperation partners. The emphasize is placed on the uncovering of the chemical and structural details of the materials, eg their morphology, defects and interfaces. Defects strongly affect the physical properties of materials, eg twin boundaries in piezoelectric materials. Quantitative structural models can be designed allowing the interpretation and simulation of high resolution contrast and the dynamic simulation of electron diffraction patterns for any zone axis. These models were created for SnO2 with the coherent twin boundary {1 0 1}, AlN with a stacking mismatch boundary caused by total displacement vector of 1/2 [1 0-1 1], ZnO showing a superposition twinning supported by a nanospike texture along the [2-1-1 3] zone axis, and (Ba0: 7Ca0: 3TiO3) 0.5-[Ba (Zr0: 2Ti0: 8) O3] 0.5 (BCZT …