Structural study of buried interface using soft X-ray emission spectroscopy

A soft X-ray emission spectroscopy (SXES) study under an energetic electron irradiation has been applied to a nondestructive buried interface analysis of a thin-film/Si (substrate) contact system, where the energy of primary electrons, Ep, is less than 20 keV. An interesting point of this method is that we can have information on the valence band density of states (VB-DOS) for each wave function for each element constructing a material under study due to the dipole selection rule in an electron transition to give rise to a photon emission, which enables us to have a specific signal for an element to be used as a finger print, otherwise it is difficult. Also, we can study an interface buried deep in a rather thick overlayer e.g. more than a hundred nm, which is due to the fact that an X-ray production depth is much larger than the mean free path of an energetic electron. Electronic structural studies of silicides by SXES are also shown.