Graded composition and valence states in self-forming barrier layers at Cu–Mn/SiO2 interface

Abstract

A self-forming diffusion barrier (SFB) layer was formed at Cu–Mn/SiO2 interface. Spatial variation of the chemical composition and valence state of the elements in the SFB was investigated in a subnanometer resolution using electron energy loss spectroscopy and transmission electron microscopy. The SFB was found to have a layered structure with graded compositions of nanocrystalline MnO and amorphous MnSiO3. The valence state of Mn was found to be +2 in the MnO layer and gradually increased to +3 in the MnSiO3 layer. The reported dielectric constant of the SFB could be explained by the observed composition and microstructure.