Ferromagnetic semiconductor EuO thin films characterized by vacuum electrochemical process with ionic liquid

Abstract

In this study, the electrochemical impedance analysis was demonstrated for thin film EuO, a ferromagnetic semiconductor, by taking the advantage of our original instrument, which enables to perform the entire process from thin film deposition to electrochemical measurement with ionic liquid in a vacuum. Effects of whether surface protecting layers were insulative or metallic, as well as their thickness on the electrochemical measurement of EuO thin films were examined by comparing the choices of amorphous alumina and Ag metal as the protecting layer. As a result, the relative permittivity of EuO films, even with a thickness of 2 nm, was successfully estimated and the averaged value was 6.6 within an error of 10 %. Furthermore, the donor density accordingly estimated was found well correlated with the Curie temperature TC of the EuO films.