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Integration of oxide-metal and nitride-metal vertically aligned nanocomposites on silicon toward device applications
Devices that can process more information in reduced dimensions are essential for an increasingly information- and efficiency-driven future. To this end, nanocomposites are promising due to their inherent multifunctional properties and special behavior at the nanoscale. Vertically aligned nanocomposites (VANs) are particularly interesting because of their ability to self-assemble into anisotropic nanostructures and high density of heterointerfaces – characteristics which introduce unique functionalities and offer exciting new avenues for device applications. However, a vast majority of VAN systems are currently fabricated on single-crystal oxide substrates, which may be cost-prohibitive at large scales and are generally incompatible with the prevalent device fabrication techniques. Thus, integration of VAN thin films on silicon becomes a critical step toward implementing VANs in a well-established semiconductor manufacturing industry.
In this dissertation, the viability of oxide-metal and nitride-metal VAN thin films integrated on silicon substrates has been demonstrated through a set of unique buffer layer designs. For the first three systems presented in this dissertation, namely, LaSrFeO4-Fe, BaTiO3-Au, and BaTiO3-Fe, microstructural and physical property (i.e. electrical, magnetic, and optical) analyses confirm their successful epitaxial growth on silicon, with only minor differences compared to their counterparts grown on single-crystal oxide substrates. For the fourth system, a new and robust TiN-Fe VAN has been proposed and demonstrated. The new TiN-Fe VAN system on Si exhibits superior magnetic properties and unusual optical properties. With further growth optimization and/or patterning techniques, VAN thin film integration on silicon presents itself as a feasible and cost-effective approach to designing electronic, spintronic, photonic, and sensing devices.