Clarification by TEM and SIMS of abnormal Ti depth distribution in chemical solution-deposited SrTiO3/La0.5Sr0.5CoO3

A chemical solution-deposited multilayer system of SrTiO3 ("STO")/La0.5Sr0.5CoO3 ("LSCO") on a platinized wafer with a layer sequence Pt/TiO2/SiO2/Si(bulk) has been investigated by dynamic SIMS (secondary ion mass spectroscopy) and TEM (transmission electron microscopy); element determination was performed with EELS (electron energy-loss spectroscopy). The STO layer is intended to serve as a dielectric layer for a microelectronic capacitor; the conducting LSCO layer is a buffer layer intended to eliminate fatigue effects which usually occur at the STO/Pt interface. The SIMS depth profiles obtained for the main components revealed intense diffusion processes which must have occurred during the deposition/crystallization processes. Ti is found to diffuse from the (insulating) STO layer into the conductive LSCO layer where a region of constant concentration is observable. TEM-EELS experiments showed that these Ti plateaus are caused by precipitates approximately 20-80 nm in diameter.