Deposition of Iron Nitride Soft Magnetic Thin Films with Giant Saturation Magnetization by Sputtering type Plasma Source

本研究尝试用溅射型等离子体源沉积大饱和磁化强度的氮化铁薄膜。溅射型等离子体源具有面向靶型高速率溅射源，从等离子体源中提取的离子可直接沉积在衬底上，尽管也有一定量的中性原子沉积在衬底上。将离子提取方法由多孔提取改为单孔提取，并提高等离子体约束磁场的强度，实现了等离子体源的改进。结果表明，在入射离子密度高达1ma /cm^2的情况下，薄膜可以沉积，靶材的寿命可以延长一个数量级以上。在不同的入射离子能量下沉积了氮化铁薄膜。沉积过程中入射到衬底的离子量也发生了变化。得到如下结果：(1)大动能离子的入射抑制了薄膜中晶体的生长。膜中的氮含量也随着入射离子能量的增加而降低。在大离子能量下沉积的氮化铁薄膜具有优异的软磁性能（饱和磁化强度：2.0 ~ 2.2 T，矫顽力<1.0 Oe）。(2)薄膜中的氮含量可通过调节氮气分气压力和衬底的偏置电压来控制。然而，本研究无法在玻片衬底上获得Fe_<16>N_2单相且饱和磁化强度大于2.8 T的薄膜。(3)入射到衬底的离子量的减少促进了薄膜中的晶体生长。这一结果表明，入射到衬底的离子增加了成核位点的密度，从而抑制了薄膜中的晶体生长。在本研究中，可以明确的是，控制入射到衬底的离子的数量和能量对于获得具有理想性能的氮化铁薄膜是非常重要的。然而，制备Fe_<16>N_2单相薄膜的沉积条件尚不清楚。少

In this research, deposition of iron nitride thin films with large saturation magnetization was attempted by means of a sputtering type plasma source. The sputtering type plasma source has a facing target type high rate sputtering source, and ions extracted from the plasma source can be deposited directly on the substrate, although some amounts of neutral atoms are also deposited on the substrate.Improvement of the plasma source was achieved by changing the ion extraction method from multi-holes to single extraction hole method, and by an increase of the strength of the plasma confinement magnetic field. As a result, the films can be deposited at an incident ion density as high as 1 mA/cm^2, and the life of the target could be prolonged by more than one order.The iron nitride films were deposited at various incident ion energies. The amount of ion incident to the substrate during deposition was also changed. Following results are obtained.(1)The incidence of ions with large kinetic ene … More rgy suppresses the crystal growth in the film. The nitrogen content in the film also decreases as the incident ion energy increases. These iron nitride films deposited at large ion energy has excellent soft magnetic properties (saturation magnetization : 2.0-2.2 T, coercive force : <1.0 Oe).(2)Nitrogen content in the film can be controlled by adjusting the nitrogen partial gas pressure and the bias voltage of the substrate. However, the film with Fe_<16>N_2 single phase that has a large saturation magnetization above 2.8 T could not be obtained on glass slide substrate in this research.(3)A decrease in the amount of ion incident to the substrate promotes a crystal growth in the film. This result suggests that the ions incident to the substrate increase the density of nucleation sites, which results in the suppression of the crystal growth in the film.In this research, it can be clarified that the control of the amount and energy of the incident ions to the substrate is very important to obtain the iron nitride films with desired properties. However, the deposition condition to obtain the Fe_<16>N_2 single phase film is still unclear. Less