Preparation and characterization of Fe4N thin film deposited by high power impulse magnetron sputtering

Abstract

In this work, high power impulse magnetron sputtering (HiPIMS) was used for the first time to grow Fe4N films. The Fe4N phase can only be formed when N is precisely at 20 at. %. Therefore, it is expected that the Fe4N phase can be obtained by optimization of growth parameters such as N2 gas flow, substrate temperature (Ts) etc. We varied process parameters and found that under optimized conditions single phase Fe4N phase can be obtained at Ts=675 K. Depth profile of Fe4N sample was studied using secondary ion mass spectroscopy and it was found that substantial inter-diffusion takes place between the substrate-film interface when Ts=675 K. This prohibits accurate estimation of saturation magnetization (Ms) by bulk magnetization methods. By using surface sensitive soft x-ray magnetic circular dichroism (MCD) we found that Ms is close to its theoretical value of about 2.5 µB/Fe atom. These are first ever MCD measurements performed on the soft x-ray absorption beamline BL-01 at Indus-2 synchrotron radiation source.In this work, high power impulse magnetron sputtering (HiPIMS) was used for the first time to grow Fe4N films. The Fe4N phase can only be formed when N is precisely at 20 at. %. Therefore, it is expected that the Fe4N phase can be obtained by optimization of growth parameters such as N2 gas flow, substrate temperature (Ts) etc. We varied process parameters and found that under optimized conditions single phase Fe4N phase can be obtained at Ts=675 K. Depth profile of Fe4N sample was studied using secondary ion mass spectroscopy and it was found that substantial inter-diffusion takes place between the substrate-film interface when Ts=675 K. This prohibits accurate estimation of saturation magnetization (Ms) by bulk magnetization methods. By using surface sensitive soft x-ray magnetic circular dichroism (MCD) we found that Ms is close to its theoretical value of about 2.5 µB/Fe atom. These are first ever MCD measurements performed on the soft x-ray absorption beamline BL-01 at Indus-2 synchrotron radiation s...