Applications of perovskite oxide thin films: microcantilevers, superconducting devices and dielectric interconnections

Abstract

The aim of this Phd is to investigate the properties of micro-cantilevers, containing BaTiO\(_3\) based capacitors on their top and verify if they can be used as energy harvesting devices. SrRuO\(_3\)/BaTiO\(_3\) systems behaving as high quality (i.e. with an impedance phase between -80° and -90°) capacitive structures, in the frequency range 6KHz - 50KHz and with a residual polarization equal to 2.5 µC/cm\(^2\) have been fabricated on 400 nm thick MgO sacrificial layer. These structures allow to design micro-cantilevers with a minimum resonance frequency of 6KHz.
Two piezoelectric modes are generally used in energy harvesting devices, they are the 33 and the 31 piezoelectric mode. X-ray diffraction analysis shows that the polar axis of BaTiO\(_3\) is perpendicular to the surface of the film when this layer is grown on SrRuO\(_3\) and SrTiO\(_3\). This configuration fits the 31 energy harvesting mode. When BaTiO\(_3\) is grown on MgO the polar axis is parallel to the surface of the film so this configuration fits the33 energy harvesting mode.
Micro-cantilevers employing YBa\(_2\)Cu\(_3\)O\(_7\) and MgO sacrificial layers have been fabricated with a technology developed for the fabrication of Nb/Au/YBa\(_2\)Cu\(_3\)O\(_7\) ramp type Josephson junctions.