Lattice strain in sputter-deposited Fe-N-Si films: effects of interstitial mobility

Fe-N-Si films have been sputter-deposited in flowing nitrogen (0.3 sccm). Asymmetric X-ray diffraction from the as-deposited films reveals interplanar spacings d/sub hkl/ that are strong functions of diffracting plane orientation /spl theta/ relative to the film surface and follow d/sub hkl//sup obs/(/spl theta/)=

+/spl Delta/d/sub hkl//sup obs/ cos 2/spl theta/. The sign of /spl Delta/d/sub hkl//sup obs/ suggests a strong biaxial compressive stress in the film plane. The /spl theta/-dependent part of d/sub 200/ is observed to be twice what it should be compared to that of d/sub 110/ based on a simple elastic analysis. By taking account of the mobility of the nitrogen interstitials, the d/sub 200/ and d/sub 110/ data become consistent, provided 10% of the nitrogen concentration in the films (10.1 atomic %) is mobile.