Raman spectroscopy study of the interface structure in (CaCuO2)n/(SrTiO3)m superlattices

TL;DR

This study uses Raman spectroscopy to investigate the interface structures in CaCuO2/SrTiO3 superlattices, revealing structural changes associated with superconductivity and demonstrating the technique's effectiveness for interface analysis.

Contribution

It provides new insights into interface structures in superlattices and shows Raman spectroscopy as a powerful method for interface characterization.

Findings

Non-superconducting superlattices show planar Cu-O coordination.

Superconducting superlattices exhibit pyramidal Cu-O coordination.

Raman shifts correlate with oxygen incorporation and superconductivity.

Abstract

Raman spectra of CaCuO2/SrTiO3 superlattices show clear spectroscopic marker of two structures formed in CaCuO2 at the interface with SrTiO3. For non-superconducting superlattices, grown in low oxidizing atmosphere, the 425 cm-1 frequency of oxygen vibration in CuO2 planes is the same as for CCO films with infinite layer structure (planar Cu-O coordination). For superconducting superlattices grown in highly oxidizing atmosphere, a 60 cm-1 frequency shift to lower energy occurs. This is ascribed to a change from planar to pyramidal Cu-O coordination because of oxygen incorporation at the interface. Raman spectroscopy proves to be a powerful tool for interface structure investigation.