INTEGRATION OF CERAMIC-METAL VERTICALLY ALIGNED NANOCOMPOSITE THIN FILMS ON FLEXIBLE MICA SUBSTRATES

Integration of functional thin films on flexible substrates has piqued interests owing to the needs of flexible devices. Selecting a suitable flexible substrate is crucial for such integration. Recently, muscovite mica has been developed as a flexible platform for functional thin film epitaxy growth. Mica can be easily peeled off due to the weak van der Waals interaction between different layers of mica, along with other advantages including cheap, high elasticity and thermal stability, biocompatible, etc. On the other hand, vertically aligned nanocomposites (VANs) have been attractive because of their unique anisotropic structures, which can achieve physical property anisotropy, easy tunability, out-of-plane strain engineering as well as combined multifunctionality. However, limited work on the integration of nanocomposite thin films on mica with tunable physical properties has been reported due to growth challenges.

In this dissertation, different ceramic-metal VAN systems integrated on mica substrates towards different functionalities using pulsed laser deposition (PLD) have been demonstrated. The first chapter is on the integration of BaTiO3-Au nanocomposite system on mica. Tunable optical properties have been achieved by controlling the geometries of the Au nanostructures between nanoparticles and nanopillars by varying the growth temperature. The laser energy was also found to play a role in terms of the Au pillar dimension. The second chapter is on the integration of BaZrO3-Co VAN system on mica towards flexible spintronics. Tunable, anisotropic ferromagnetic property has been realized by controlling the aspect ratio of the Co pillars. The third chapter is on integration of BaTiO3-Fe VAN system on mica towards multiferroics. Different buffer layers have been tried out to facilitate the growth of VAN structure. Room temperature ferroelectric and anisotropic ferromagnetic properties of the films have been confirmed. The last chapter is focused on multiphase nitride-metal nanocomposite design and integration, with films showing unique optical and magnetic properties. The reliability and stability of the physical properties of the films have been verified though bending tests. The growth mechanism and criteria of ceramic-metal nanocomposite on mica have also been discussed. These demonstrations all pave a new way towards the integration and design of multifunctional nanocomposites towards flexible nanodevices.