Nucleation processes of mixed-phase states are an intrinsic characteristic of first-order phase transitions, typically related to local symmetry breaking. Direct observation of emerging mixed-phase regions in materials showing a first-order metal–insulator transition (MIT) offers unique opportunities to uncover their driving mechanism. Using photoemission electron microscopy, we image the nanoscale formation and growth of insulating domains across the temperature-driven MIT in NdNiO3 epitaxial thin films. Heteroepitaxy is found to strongly determine the nanoscale nature of the phase transition, inducing preferential formation of striped domains along the terraces of atomically flat stepped surfaces. We show that the distribution of transition temperatures is a local property, set by surface morphology and stable across multiple temperature cycles. Our data provide new insights into the MIT of heteroepitaxial nickelates and point to a rich, nanoscale phenomenology in this strongly correlated material.

(001) oriented L10 FePt/B4C multilayer thin films on naturally oxidized Si substrate J. Appl. Phys. 113, 17C108 (2013) Multiple oxide content media for columnar grain growth in L10 FePt thin films Appl. Phys. Lett. 102, 112411 (2013) Magnetic and high frequency properties of nanogranular CoFe-TiO2 films J. Appl. Phys. 113, 17A316 (2013) Low substrate temperature fabrication of high-performance metal oxide thin-film by magnetron sputtering with target self-heating Appl.

There is much interest in interfaces between insulating oxides, such as SrTiO3 (STO) and LaAlO3 (LAO), where a two dimensional electron gas can form due to the so-called polar discontinuity. These interfaces are mostly fabricated by Pulsed Laser Deposition (PLD). We have investigated such interfaces by reactive RF sputtering in a high-pressure oxygen atmosphere. The films are smooth and crystalline. Transmission Electron Microscopy indicates that the interfaces are sharp and continuous while Electron Energy Loss Spectroscopy data indicate some slight intermixing. However, we find these interfaces to be non-conducting. It appears that the sputtered interface is not electronically reconstructed in the way reported for films grown by PLD, notwithstanding the good structural quality and composition of the films.

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