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中。存在铁磁和反铁磁耦合的可能性。这有助于在金属超晶格薄膜中观察到的巨磁阻效应。可以通过激光束照射进行切换。这种半导体可以通过光子或热激发来控制导电载流子密度。因此，预期铁磁层之间的磁耦合将通过半导体层的激励而改变。本研究选用β-FeSi_2作为半导体材料，是因为β-FeSi_2与其它材料相比具有以下优点：（1）由于其高吸收系数和直接光学带隙，对电子束辐照具有高灵敏度。(2)由于β-FeSi_2的高电导率，使更多的电子可以穿过层间，从而使铁磁耦合和反铁磁耦合的电阻变化较大。 ...更多信息 多层膜。优选各层的低温生长以防止层间的原子扩散。但是，β-FeSi_2的生长需要800℃的高温。因此。本文采用高能激光沉积法（脉冲激光沉积法和射频磁控溅射法）在Si（100）基片上制备了β-FeSi_2薄膜，并在此基础上研究了β-FeSi_2薄膜的制备方法。在20℃的衬底温度下也能形成β-FeSi_2相的多晶薄膜。在衬底温度超过100℃时。可以获得显示光学带隙的膜。在沉积的薄膜中。直径为1-10 μm的球形液滴。由于表面熔化而从靶中喷出。偶尔会被观察到。这些液滴严重破坏胶片质量。因此，我们设计并制造了旋转过滤器，并试图在液滴到达基底之前捕获液滴。使用SEM观察在各种过滤器旋转下沉积的膜的膜表面，并估计各种液滴尺寸的液滴速度。随着液滴尺寸的减小，液滴数目增加，速度加快。结果表明，熔滴的速度最大可达100 m/s，比烧蚀粒子的速度低两个数量级，因此可以用熔滴过滤器完全捕获熔滴。但它们不可能是生长的。因此，我们放弃了射频磁控溅射制备多层膜的应用。制备了Fe/β-FeSi_2/Fe三明治薄膜。然而，不能获得指示反铁磁耦合的膜。β-FeSi_2层厚度与磁耦合的关系有待进一步研究。在本研究中，我们得到了达到目的的基础性成果，但目前还只是起步阶段。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