X-ray photoelectron and X-ray absorption spectroscopic study on β-FeSi2 thin films fabricated by ion beam sputter deposition

A combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is applied to clarify surface chemical states of β-FeSi2 films fabricated by an ion-beam sputtering deposition method. The differences in the chemical states of the films fabricated at substrate temperatures of 873, 973 and 1173 K are investigated. For the film fabricated at 873 K, Si 2p XPS spectra indicate the formation of a relatively thicker SiO2 layer. In addition, Fe L-edge XAS spectra exhibit the formation of FeSi2−X by preferential oxidation of Si or the presence of unreacted Fe. The results for the film fabricated at 1173 K imply the existence of FeSi2 with α and ɛ phases. In contrast, the results for the film fabricated at 973 K indicate the formation of relatively homogeneous β-FeSi2. These imply that the relatively excellent crystal property of the film fabricated at 973 K is due to the formation of homogeneous β-FeSi2. As a conclusion, the combination of XPS and XAS using synchrotron radiation is a powerful tool to elucidate the surface chemical states of thin films.