X-ray absorption fine structure analysis of functional thin films

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Some of the thin films of a few micrometers in thickness are important materials for magnetic information storage devices, sensors, surface coating for optical devices, plating for corrosive metals, etc. In order to improve the functions of these thin films the information of their atomic scale structures is crucial. However, it is often difficult to obtain structural information of very thin films deposited on thick substrates. The purpose of this research is to investigate these thin films by X-ray absorption fine structure (XAFS) analysis which is known to be useful for studying the local atomic structure. XAFS is normally obtained by transmission method, thus it is difficult to be applied to thin films on thick substrate. Here the XAFS spectra are obtained by total-conversion electron-yield method (TCEY). Since the mean free path of Auger electrons is less than a few micrometers, TCEY-XAFS method is useful for the study of surface materials.TCEY-XAFS of deposited thin films of SrTiO_3 on single crystals, LaAIO_3 and MgO, as substrates have been studied. From the XAFS signal intensities for several samples with different thicknesses, Sr K- and Ti K-edge detecting depths are found to be 300 nm and 30 nm, respectively. The EXAFS analyses for Sr and Ti in thin films concluded that the local structure of Sr changes with the film thickness, but that of Ti does not.Amorphous iron silicates or iron nitrides are interesting magnetic materials. They can be deposited on glass by sputtering method. Their local structures are compared with those in bulk samples. The TCEY-XAFS spectroscopy is especially suitable for these amorphous deposited materials.