A Moessbauer comparative study of the local environment in metastable 304 stainless steel films depending on the preparation mode

The structure and local environment in metastable 304 stainless steel films grown by thermal evaporation was examined by X-ray diffraction and conversion electron Moessbauer spectroscopy, and compared with previous results on ion-beam sputtered films. While in both cases the dominant structure is the strongly ferromagnetic α-phase, evaporated films exhibit ∼9.5 vol% of the paramagnetic γ-phase, and an enlarged hyperfine magnetic field distribution as well. For sputtered films, the 20 deg. C Moessbauer spectrum can be fitted assuming a random solid solution with only one ferromagnetic Fe-site. On the contrary, for evaporated films, the ferromagnetic component of the spectrum requires a model assuming two different Fe-sites to be reproduced. It can be concluded that sputtered films are in a state further away from equilibrium than after preparation by thermal evaporation. The differences can be explained by the higher energy of the deposited atoms in the ion-beam sputtering process