Effect of polar discontinuity on the growth of LaNiO3/LaAlO3 superlattices

TL;DR

This study investigates how polar mismatch affects the growth and properties of LaNiO3/LaAlO3 superlattices, revealing that substrate polarity influences morphology, valence states, and structural adaptation during growth.

Contribution

It introduces a new model explaining how polar mismatch is resolved through LaO excess growth, impacting electronic and structural characteristics.

Findings

Growth on SrTiO3 results in rough morphology and Ni valence of 2+.

Growth on LaAlO3 yields smoother layers with different electronic properties.

A model suggests polar mismatch is mitigated by LaO excess layers.

Abstract

We have conducted a detailed microscopic investigation of [LaNiO3(1 u.c.)/LaAlO3(1 u.c.)]N superlattices grown on (001) SrTiO3 and LaAlO3 to explore the influence of polar mismatch on the resulting electronic and structural properties. Our data demonstrate that the initial growth on the non-polar SrTiO3 surface leads to a rough morphology and unusual 2+ valence of Ni in the first LaNiO3 layer, which is not observed after growth on the polar surface of LaAlO3. A newly devised model suggests that the polar mismatch can be resolved if the perovskite layers grow with an excess of LaO, which also accounts for the observed electronic, chemical, and structural effects.