Change of electric resistance induced by laser irradiance due to spin dependent electron scattering in β-FeSi_2 Fe multi-layered films

在铁磁金属半导体多层膜。存在铁磁与反铁磁耦合的可能性。这是在金属超晶格薄膜中观察到的巨大磁阻效应的原因。可通过激光束辐照度进行切换。半导体可以很容易地利用光子或热激发来控制载流子密度。因此，半导体层的激发有望改变铁磁层之间的磁耦合。在这项研究中。我们选择β-FeSi_2作为半导体材料，是因为与其他材料相比，β-FeSi_2具有以下优点：(1)由于高吸收系数和直接光学带隙，对光束辐照具有高灵敏度。(2)由于β-FeSi_2的高导电性，使得铁偶联和反铁偶联的电阻值比其他半导体材料的电阻值变化大。在制造…更多的多层薄膜。为了防止层间原子扩散，每层宜低温生长。然而，众所周知，β-FeSi_2的生长需要800℃这样的高温。因此。本文尝试采用脉冲激光沉积和射频磁溅射两种高能量沉积方法制备β-FeSi_2薄膜。以FeSi_2合金为靶材，采用脉冲激光沉积技术在Si（100）衬底上制备了脱硅化铁薄膜。在20℃的衬底温度下，β-FeSi_2相也能形成多晶薄膜。衬底温度超过100℃时。可以得到显示光学带隙的薄膜。在沉积的薄膜中。直径为1 ~ 10 μm的球形液滴。由于表面融化而从目标中喷射出来。偶尔被观察到。这些液滴强烈地破坏了薄膜的质量。因此，我们设计并制造了旋转过滤器，并试图在液滴到达基板之前捕获液滴。利用扫描电镜观察了在不同滤光片旋转下沉积的薄膜表面。并对不同粒径的液滴速度进行了估计。随着液滴尺寸的减小，液滴的数量增加，速度加快。结果表明，它们的速度最大可达100m /s。这比烧蚀物质小两个数量级，因此使用液滴过滤器可以完全捕获液滴。采用射频磁控溅射法制备了脱硅化铁薄膜。但他们不能像以前那样长大。因此，我们放弃了射频磁控溅射制备多层薄膜的应用。采用脉冲激光沉积。我们正在制备Fe/β-FeSi_2/Fe夹层膜。但无法得到表明反铁磁耦合的薄膜。β-FeSi_2层厚度与磁耦合之间的关系有待进一步研究。在这项研究中。我们得到了达到目的的基本结果，但它现在是开始的平面。到目前为止。我们继续这项研究。少

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 … More 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