Transport properties of microstructured ultrathin films of La0.67Ca0.33MnO3 on SrTiO3

TL;DR

This study examines the electrical transport and magnetoresistance of ultrathin La0.67Ca0.33MnO3 films on SrTiO3, revealing effects of etching, recovery processes, and temperature-dependent non-linearities.

Contribution

It provides new insights into how etching and recovery processes affect the transport properties of ultrathin manganite films on STO substrates.

Findings

Slight overetching causes substrate conductance and non-linear I-V characteristics.

Oxygen plasma etching restores insulating behavior and linear I-V response.

Colossal magnetoresistance observed without electroresistance effects.

Abstract

We have investigated the electrical transport properties of 8 nm thick La0.67Ca0.33MnO3 films, sputter-deposited on SrTiO3 (STO), and etched into 5 micrometer-wide bridges by Ar-ion etching. We find that even slight overetching of the film leads to conductance of the STO substrate, and asymmetric and non-linear current-voltage (I-V) characteristics. However, a brief oxygen plasma etch allows full recovery of the insulating character of the substrate. The I-V characteristics of the bridges are then fully linear over a large range of current densities. We find colossal magnetoresistance properties typical for strained LCMO on STO but no signature of non-linear effects (so-called electroresistance) connected to electronic inhomogeneites. In the metallic state below 150 K, the highest current densities lead to heating effects and non-linear I-V characteristics.