Evidence of strain induced structural change in hetero-epitaxial NdNiO₃ thin films with metal-insulator transition

¹ Laboratoire de Physique de l'État Condensé, UMR CNRS 6087, Université du Maine, avenue O. Messiaen, 72085 Le Mans Cedex, France
² EMAT, University of Antwerp, Groeonenborgerlaan 171, 2020 Antwerp, Belgium
³ Laboratoire de Physico-Chimie des Interfaces et Applications, Université d'Artois, rue Jean Souvraz, SP 18, 62307 Lens Cedex, France
⁴ Exp. Cond. Matter Physics Division, Saha Institute of Nuclear Physics 1/AF Bidhan Nagar, Calcutta 700064, India

Corresponding author: patrick.laffez@univ-lemans.fr

Received: 13 January 2003
Revised: 14 October 2003
Accepted: 17 October 2003
Published online: 2 December 2003

Abstract

Neodymium nickelate thin films have been prepared on NdGaO₃ substrates by RF magnetron sputtering and post-annealing treatment under oxygen pressure. Transport properties are found to depend strongly on film thickness. Thick films show transport properties close to bulk ceramics, while very thin films exhibit a large transition from metal to insulator which occurs over a wide temperature range with high resistivity. Structure and surface morphology of the films have been investigated by Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). Thin films (≈17 nm) grow heteroepitaxially, while thicker films (≈73 nm) show a granular structure. The thinnest sample suggests a symmetry change induced by the epitaxial strain of the substrate. This paper discusses the relationship between microstructure and transport properties.