The morphological, structural and physical properties of ultra-thick C-axis oriented barium ferrite films.

摘要

Nowadays most of the existing circulators and phase shifters are the building blocks of high-performance phased-array radars and communications systems. Ferrite reciprocal and nonreciprocal components currently used in transmit/receive (T/R) modules, however are costly and bulky. The focus of this work was a detailed in-depth investigation of the phenomena surrounding the growth, characterization and modeling of ultra-thick film C-axis oriented Barium Hexaferrite films, which will integrate excellent magnetic properties, miniature size and low losses.; Polycrystalline structures have been engineered using the Pulsed Laser Deposition (PLD) and Modified Liquid Phase Epitaxy (MLPE) reflow techniques. Unfortunately the Plasma Enhanced Chemical Vapor Deposition (PECVD) showed only mediocre physical quality and magnetic properties of the films do not support a further pursue of these techniques. This research introduces the novel Modified Injection Molding (MIM) technique for fabrication of ultra-thick M-type Barium Ferrite films that can be possibly utilized as monolithic microwave integrated circuits (MMIC) devices with operating range from 1 to 100GHZ. This is an extremely low cost production, with very high rate of repetition and success. The fabricated magnetic pucks show an average coercivity of 4500 Oe, a squareness SQ= Mr/Ms = 0.93 and a magnetization saturation 4piM S above 4500 Gauss. Polycrystalline self-biased BaM films with thickness of up to 2mm have been compared to films produced by PECVD, PLD and MLPE grown samples on different substrates. Due to the low growth rate, the PECVD and PLD techniques should not be considered for industrial application. The MLPE technique has shown some very promising signs: polycrystalline films, and excellent c-axis orientation of the magnetic moment. The coercivity of the MLPE grown thick films > 400 micron was found to be about 700 Oe. The films obtained using MIM give unlimited physical dimensions of the fabricated films. For actual simulation and possible application as a monolithic microwave integrated circuit device, a BaFe12O19 puck was fabricated with thickness of 500 mum and a radius of 450 mum. The research conducted shows this new technique will prove to be cost effective and with much higher efficiency than the other conventional techniques for thin film fabrication.