Fabrication of Highly Oriented Fe Films by Thermal CVD with Imposition of Magnetic Field

本研究采用CVD反应体系，以氢（H_2）还原氯化铁（FeCl_3）。在CVD过程中，施加稳定磁场。首先采用非超导磁体施加0.5T确定基本沉积条件，然后建立XRD、TEM、FE-SEM等微观结构表征方法。第二阶段，将CVD装置放置在东北大学材料研究所超导材料高场实验室安装的超导磁体上。研究了铁薄膜的制备及其微观结构和晶体取向的表征。所得结果总结如下：1。结果表明，随着磁场强度的增大，FeCl_3的汽化量增大。这种趋势在5t以上尤为明显。首先形成岛状晶体，然后通过它们的聚并形成薄膜。这种类型的生长模式可能是由于铁晶体在非晶SiO_2衬底上难以成核。随着磁场强度的增加，立方状岛状晶体的比例增加。同时，（100）取向度增加，这与铁晶体的易磁化轴一致。磁场的施加可能会诱发优选形核。当岛状晶体转变为薄膜时，（100）取向度降低。由于衬底温度较高（~ 0.5Tm），薄膜具有III区晶粒结构。薄膜中晶界迁移现象的发生可能与（100）织构的消失有关。

In this research, CVD reaction system of reducing iron chloride (FeCl_3) with hydrogen (H_2) was utilized. During the CVD process, steady magnetic field was imposed.Fist of all, fundamental deposition conditions were determined by imposition of 0.5T with non-superconducting magnet, then the microstructural characterization methods were established, such as XRD, TEM and FE-SEM.In the second stage, CVD apparatus was placed in the superconducting magnet installed in High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University. Fabrication of Fe films and characterization of their microstructure and crystal orientation were conducted. The obtained results are summarized as follows :1. It was found that the vaporized amount of FeCl_3 increased as an increase of magnetic field intensity. Especially, this tendency was obvious above 5T.2. Island-shaped crystals are formed first, then the films are formed through their coalescence occurs. This type of the growth mode might be due to difficulty in nucleation of Fe crystals on an amorphous SiO_2 substrate.3. Fraction of cube-shaped island-shaped crystals increased, as an increase of magnetic field intensity. Simultaneously, degree of (100) orientation increased, which is consistent with the easy- magnetization axis of iron crystals. The preferred nucleation might be induced by the imposition of the magnetic field.4. Degree of (100) orientation decreased when island-shaped crystals changed to films. The films have Zone III grain structure because of the relatively high substrate temperature (〜0.5Tm of Fe). Occurrence of considerable grain boundary migration in the films might be related to the disappearance of (100) texture.