Preparation of stable iron nitride films by high speed reactive sputtering

氮化铁薄膜是一种很有前途的记录材料。特别是γ - fe_4n复合薄膜具有较大的饱和磁化强度和合理的矫顽力，有望成为一种新的记录介质。在实际应用中，薄膜的织构（包括晶粒尺寸）和在高温下的相稳定性对获得合适的薄膜性能非常重要。因此，本项目通过以下两个步骤进行：一是寻找一种简单/有效的制备方法，二是利用上述方法控制沉积参数，建立结构稳定的氮化铁薄膜的合适制备条件。主要研究结果如下：在溅射过程中向溅射氩气中加入氮气，有效地改进了双面靶型直流溅射装置，制备了氮化铁薄膜。一对直径为10 cm的铁靶非常有效地获得了高沉积速率和高电源。沉积膜中的氮含量受到沉积参数的控制，但在此条件下不能生成Fe16N2化合物。砷沉积膜是亚稳态的，很容易转变成另一种稳定相。在200℃以上的高温下，可以制备出稳定的氮化铁薄膜。这种基片加热系统在实际薄膜制作中必须加以考虑。这里采用的高疏散系统有效地减少了残留杂质气体以及总薄膜制备时间。以产生更稳定的。然而，氮化铁薄膜与衬底之间的关系必须考虑：氮化铁薄膜与衬底晶体之间的晶格对应可能是最重要的因素之一。

Iron nitride films are promising recording materials. Especially, ganma-Fe_4N compound film is expected as one of new recording media because of large saturation magnetization with a reasonable coercive force. In practice, film texture including grain size and the phase stability at elevated temperatures are very important to get appropriate film properties. Therefore, this project was carried out through two following steps: One is to find a simple/effective preparation method, and the other is to establish suitable preparation conditions for structure-stable iron nitride films by controlling deposition parameters using the above method. Main results are as follows: A two-facing target type dc sputtering apparatus was effectively modified so as to prepare iron nitride films by adding a nitrogen gas to a sputtering argon gas during sputtering. A pair of iron target 10 cm in diameter was very effective to get a high deposition rate together with high power supply. Nitrogen content in deposited films was found to be controlled well by deposition parameters, although Fe16N2 compounds were not produced under the present conditions. As-deposited films were metastable and were easily transformed into another stable phase. Stable iron nitride films were found to be prepared at elevated temperatures more than 200ﾟC. This substrate heating system must be taken into consideration in practical film fabrication.A high evacuation system employed here vas effective to reduce a residual impurity ga s as well as a total film preparation time. In order to produce more stable. iron nitride films, however, a relationship between the deposited film and the substrate must be taken into consideration: The lattice corresponderxe between the iron nitride film and the substrate crystal may be one of the most important factors.