| Project/Area Number |
11650018
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
YOSHITAKE Tsuyoshi KYUSHU UNIVERSITY Faculty of Eng.Sci., Ass.Prof., 大学院・総合理工学研究院, 助教授 (40284541)
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| Co-Investigator(Kenkyū-buntansha) |
NAGAYAMA Kunihito KYUSHU UNIVERSITY, Faculty of Eng.. Prof., 大学院・工学研究院, 教授 (20040446)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2000: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1999: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | Fe / Silicide / sputtering / Ablation / Multi-layered film / droplet / β-FeSi_2 / semiconductor / 人工格子 / スピン依存散乱 / 強磁性交換結合 |
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| Research Abstract |
In ferromagnetic metal semiconductor multi-layered films. there is the possibility that the ferro and anti-ferromagnetic couplings. which contribute to the giant magnetic resistance effect observed in metallic superlattice films. can be switched by laser beam irradiance. The semiconductors can control conduction carrier density by the photon or thermtal excitation easily. Thus the magnetic coupling between ferromagnetic layers is expected to be changed by the excitation of the semiconducting layers. In this study.we adapted the β-FeSi_2 as a semiconducting material because the β-FeSi_2 has the following advantage compared with other materials : (1) high sensitive for the beam irradiation due to high absorption coefficient and direct optical band gap. (2) large change of electric resistance for the ferro and anti-ferro couplings because more electrons can across the layers than those of other semiconducting materials due to high electrical conductivity of β-FeSi_2.
In the fabrication of
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multi-layered films. low temperature growth of each layer is preferable in order to prevent from the atomic diffusion between layers. However it is known to that the high temperatures such as 800℃ are necessary for β-FeSi_2 to be grown. Hence. we attempted to grom β-FeSi_2 thin films using the high energetic deposition methods : those are the pulsed laser deposition and the RF magnetic sputtering methods.
Iron desilicide thin films were prepared by pulsed laser deposition on Si (100) substrates using a FeSi_2 alloy target. Polycrystal films of β-FeSi_2 phase could be formed even at a substrate temperature of 20℃. At substrate temperatures more than 100℃. the films showing the optical band gap could be obtained. In the deposited films. spherical droplets with a diameter of 1-10 μm. which are ejected from the target due to melting of the surface. were observed occasionally. These droplets spoil strongly the film quality. Thus we designed and fabricated the rotation filter and attempted to capture the droplets before their arriving at the substrate. The film surface was observed for the films deposited at various filter rotations, using a SEM.and the droplet velocities for various droplet sizes were estimated. The number of droplets increases and the velocity get faster with the droplet size decreases. It is found that their velocity is 100 m/s at most.which is two orders of magnitude solwer than that of ablation species and thus the droplets can be captured completely using the droplet filter.
Iron desilicide thin films were also prepared by RF magnetron sputtering. but they could not be as-grown. Thus we abandoned the application of RF magnetron sputtering for fabricating the multi-layered films.
Using the pulsed laser deposition. we are fabricating the Fe/β-FeSi_2/Fe sandwiched films. however the films indicating the anti-ferromagnetic coupling could not be obtained. The relation between the thickness of β-FeSi_2 layer and the magnetic coupling should be investigated in detail. In this study.we got the basis result for attaining the purpose but it is the beginning plane now.As of now. we continue this research. Less
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