Nanoscale characterization of interfacial reactions in SrRuO3 thin film on Si substrate

Abstract

Interfacial reactions between SrRoO(3) films and Si substrate were investigated by using field-emission transmission electron microscopy (FE-TEM). The compositional and structural variations across the interface were analysed using energy-dispersive x-ray spectroscopy (EDS) and diffraction methods with an electron probe of 0.5 nm diameter. According to the morphology and composition analysed, the reaction layers between Si and SrRuO3 (from the substrate side) were identified as follows: Sr-Si-O layer; amorphous SiO2 layer; Sr-Si-O layer; and nanometre-sized Ru-rich grains containing Si and O. The reaction layers and their characteristics could be explained by considering the chemical reactivity of the binary constituent oxides of SrRuO3 (i.e. SrO and RuO2) with Si substrate: i.e. SrO can be stable in contact with Si because the Sr-Si-O ternary system has a stable tie-line between SrO and Si, but RuO2 cannot be stable with Si because the Ru-Si-O ternary system has a stable tie-line not between RuO2 and Si but between Ru and SiO2. The reduction of SrRuO3 to elemental Ru by Si is believed to be the most favourable candidate for the reaction leading to the unstable contact of SrRuO3 on Si. Copyright (C) 2001 John Wiley & Sons, Ltd.