Interface interaction of Co atop Bepp2 with different substrate temperatures

Abstract

The interaction at organic–ferromagnetic interfaces in organic spin-valves has a considerable effect on efficient spin injection or detection. In this work, Al/Co films were deposited on the organic Bepp2 layers at two different substrate temperatures to investigate the interface interaction. The interaction including penetration, interdiffusion and chemical reaction has been studied by the surface morphology measurement, X-ray photoelectron spectroscopy combined with Argon ion etching technique and magnetic properties measurement. It was found that the interfacial penetration and chemical reaction were serious, forming plenty of holes and non-ferromagnetic metallic carbide and oxides owing to the high energy of sputtered Co atoms into the organic Bepp2 layer when depositing Co on Bepp2 layer at the substrate temperature of 24°C. However, this phenomenon weakened when lowering the temperature to −13°C. Our results show that the low substrate temperature can reduce the penetration of the top metal electrode into the organic layer and weaken the chemical reaction between the top electrode and organic layer, which could pave a way for obtaining high-spin injection and extraction efficiency in organic spin-valve devices.