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GaN-Fe_4 N复合薄膜由于具有较大的饱和磁化强度和合理的矫顽力，有望成为一种新型的磁记录介质。在实践中，薄膜织构包括晶粒尺寸和高温下的相稳定性对于获得合适的薄膜性能是非常重要的。因此，本课题主要从以下两个方面展开：一是寻找一种简单有效的制备方法，二是利用上述方法通过控制沉积参数建立合适的制备条件，制备结构稳定的氮化铁薄膜。主要结果如下：对双面靶型直流溅射装置进行了有效的改进，以便通过在溅射期间向溅射氩气中添加氮气来制备氮化铁膜。一对直径为10 cm的铁靶在高功率下可有效地获得高沉积速率。沉积膜中的氮含量被发现控制以及沉积参数，虽然Fe 16 N2化合物在本条件下没有产生。沉积膜是亚稳态的，并且容易转变成另一种稳定相。在超过200摄氏度的高温下可以制备稳定的氮化铁薄膜。在实际的薄膜制备过程中，必须考虑这种衬底加热系统，采用高真空系统可以有效地减少残余杂质气体，缩短薄膜制备时间。为了生产更稳定。然而，在制备氮化铁薄膜时，必须考虑沉积薄膜与衬底之间的关系：氮化铁薄膜与衬底晶体之间的晶格对应关系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.