Electronic inhomogeneity and band structure on superstructural CuO2 planes of infinite-layer Sr0.94La0.06CuO2+y films

TL;DR

This study uses scanning tunneling microscopy to explore the atomic structure and electronic inhomogeneity of Sr0.94La0.06CuO2+y films, revealing superstructural modulations, in-gap states, and doping effects on the CuO2 planes.

Contribution

It provides detailed atomic-scale insights into the superstructural and electronic properties of infinite-layer cuprate films, highlighting the relationship between oxygen doping and electronic inhomogeneity.

Findings

Identification of incommensurate supermodulation with 24.5 Å period.

Observation of substantial nanoscale electronic inhomogeneity.

Detection of in-gap states emerging with doping.

Abstract

Scanning tunneling microscopy and spectroscopy are utilized to study the atomic-scale structure and electronic properties of infinite-layer Sr0.94La0.06CuO2+y films prepared on SrRuO3-buffered SrTiO3(001) substrate by ozone-assisted molecular beam epitaxy. Incommensurate structural supermodulation with a period of 24.5{\AA} is identified on the CuO2-terminated surface, leading to characteristic stripes running along the 45o direction with respect to the Cu-O-Cu bonds. Spatially resolved tunneling spectra reveal substantial inhomogeneity on a nanometer length scale and emergence of in-gap states at sufficient doping. Despite the Fermi level shifting up to 0.7 eV, the charge-transfer energy gap of the CuO2 planes remains fundamentally unchanged at different doping levels. The occurrence of the CuO2 superstructure is constrained in the surface region and its formation is found to link with oxygen intake that serves as doping agent of holes in the epitaxial films.