| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 95 === The purpose of this thesis was to develop magnetic thin films for high frequency applications. We made of Fe-Y-B bulk metallic glasses that had developed in our laboratory. The study was divided into three parts: First, the Fe-Y-B ternary system. Second, the Fe-Y-B films which were annealed under a magnetic field after sputtering. Third, Fe-Y-B-M quaternary system. Electrical, magnetic and high frequency properties of these films were evaluated.
Amorphous Fe-Y-B thin films were sputter-deposited using composite target with Y chip on a Fe80B20 target with area ratio of Y 5.6 %. The films obtained at a dc power of 40 W showed a resistivity ρ ~ 860 μΩ-cm, 4πMs ~ 1.01 T and Hc ~ 27 Oe. The film was also shown to have a high resonance frequency fr ~ 2.1 GHz. No magnetic uniaxial anisotropy was found in the as-deposited films. The thin films obtained at a dc power of 80 W showed a resistivity ρ ~ 340 μΩ-cm, 4πMs ~ 0.86 T and a low Hc ~ 1.5 Oe. The film also had a fr ~ 1.0 GHz and a very high μ’ above 700 which remain nearly constant up to ~ 0.75 GHz.
The thin films obtained at a dc power of 60 W with Y chip on a Fe80B20 target with area ratio of Y 9 % were taken to anneal under 2500 G. Nano-grained α-Fe appealed after field annealing at 300 oC for 30 min. All films demonstrated a minor crystalline growth and good thermal stability up to 500oC for 30 min. Above 300 oC, a small increase occurred in crystallite size from 5 nm up to 6.7 nm at 500 oC. The film after 450 oC field-annealing for 30 min showed good high frequency property with Ms ~ 1.07 T, Hc ~ 66.3 Oe and fr > 3 GHz. The corresponding values were Ms ~ 1.08 T, Hc ~ 47 Oe, fr ~ 2.7 GHz for film after 400 oC field-annealing for 2 hr. The appearance of nano-grained α-Fe after field-annealing is showed beneficial to promote the high frequency properties.
The quaternary films showed inferior properties. In summary the Fe-Y-B films showed high resistivity and high frequency properties, which are promising for high frequency applications.
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