Zinc oxide (ZnO)-based nanocomposites, specifically vertically aligned nanocomposites (VAN), are a unique type of thin film architecture. The large anisotropy, strain, and property tuning capabilities in these thin films are simply due to growing ZnO with another material that has its own interesting properties. Previous research has been conducted with ZnO-based VAN, but many gaps still remain such as mixing of different materials, composition tuning, and integration of VAN into multilayer films, to name a few. The goal of this thesis work is to fill in these gaps and gain a better understanding on how the ZnO-based nanocomposites grow and what possible applications they show promise in. Optical, magnetic, and electrical properties have been explored in various ZnO-based nanocomposite systems and have shown tuning based on different parameters.

 

The first part of the thesis investigates the influence of Au concentration on the microstructure and optical properties of ZnO-Au vertically aligned nanocomposite thin films such as optical permittivity and surface plasmon resonance. It demonstrates how strain-driven tuning of optical properties and microstructure can result through this Au concentration variation approach, which has not been previously attempted in the ZnO-Au thin film system. Thus, this demonstration makes the ZnO-Au films practical for plasmonic sensing and nanophotonic applications.

 

The second project of the thesis focuses on ZnO-Ni VAN. It investigates the influence of vacuum pressure and a ZnO-Au seeding layer on the microstructure, optical permittivity, transmittance, and magnetic properties of ZnO-Ni VAN thin films. Results demonstrate control over Ni phase formation, epitaxial growth, and ZnO-Ni microstructure using vacuum pressure and seeding layers, achieving novel and unique core-shell and 'nanocup' structures.

 

The third project covers ZnO-BTO (Barium Titanate) VAN growth. It investigated the impact of PLD laser frequency tuning on microstructure, piezoelectric, and ferroelectric properties of ZnO-BTO grown on both sapphire and STO substrates. This expanded the scope of ZnO-oxide nanocomposites by integrating ferroelectric barium titanate (BTO) with ZnO, addressing the limited diversity of oxides and PLD parameter tuning in the ZnO system.

 

Lastly, the final part of the thesis incorporated the VAN structure in a multilayer stack with ZnO-Ni and Lithium Niobate (LNO). The number of layers and the order of them demonstrated tunability of the magnetic, optical, and ferroelectric properties in the film. This demonstration shows the potential of incorporating magnetic nanostructures in LNO thin films for future photonic waveguides and acoustic device applications.