Nian Xiang Sun
Katherine S. Ziemer, Philip E. Serafim
Date of Award
Doctor of Philosophy
Department or Academic Unit
College of Engineering, Department of Electrical and Computer Engineering
electrical engineering, materials science, Low-temperature process, Magnetic Materials, Novel RF Ferrites, Semiconductor Materials, Spin-spray deposition process
Electrical and Computer Engineering
High frequency operation of magnetic materials has received much attention in the microwave and telecommunication industries. Ferrite materials are one of the most widely used materials due to their high permeability and resistivity at high frequency range. In thin film form, they provide a unique opportunity for microwave device application in GHz range due to their significantly extended Snoek limit. In this research, novel RF ferrites by the direct deposition spin-spray process were synthesized and characterized.
Spin-spray deposition process unlike the other conventional techniques, is a low cost (no vacuum required), low temperature process (OC) which is compatible with a wide range of substrates like organic materials, plastics, RFIC and MMIC etc.
Properties of these spin-spray synthesized ferrites required for RF/microwave applications were examined. Strong interface adhesion in Ni0.23Fe2.77O4/PZT (lead zirconium titanate) and magnetoelectric (ME) coupling leading to record-high electrostatic field induced ferromagnetic magnetic resonance (FMR) field change of 860 Oe, microwave ME coefficient of 108 Oe cm/kV and FMR microwave tunability of 1450 Oe were achieved in Fe3O4/PZN-PT multiferroic heterostructure. These properties will enable low temperature fabrication of electrostatic tunable microwave devices. Nickel zinc (NiZn) ferrite films with high permeability that exceeded the Snoek's limit for bulk NiZn-ferrite films and those previously reported for spin-spray deposited ferrites, and with low magnetic losses in the GHz range were also developed.
Thicker ferrite film loading, which could lead to an even greater performance enhancement in RF/microwave devices, have been difficult to achieve due to their degraded RF performance. Ferrite/non-magnetic multilayers serve as a good solution to this problem. Spin-spray deposited two-period ferrite/non-magnetic multilayer films with significant enhancement in RF/microwave magnetic properties over their single layer counterparts were fabricated and extensively characterized.
Furthermore, novel RF devices with improved performance such as miniaturization, bandwidth enhancement, directivity and gain improvement were developed using these ferrites.
Lastly, a study into spin-spray processing condition effects on semiconductor zinc oxide (ZnO) microstructures was successfully carried out. Though the spin-spray process was initially developed for ferrite making, it is currently been explored as a growth technique for ZnO micro/nanostructures.
Ogheneyunume Ighogbedhe Obi
Obi, Ogheneyunume Ighogbedhe, "Synthesis, characterization and applications of novel RF ferrites by low-temperature spin-spray deposition" (2011). Electrical Engineering Dissertations. Paper 39. http://hdl.handle.net/2047/d20001154
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