Revealing the role of interfacial heterogeneous nucleation in metastable thin film growth of rare earth nickelates electronic transition materials

TL;DR

This study demonstrates that heterogeneous nucleation enables the growth of metastable rare earth nickelate thin films at atmospheric pressure, with high oxygen pressures necessary to induce electronic transitions by eliminating oxygen vacancies.

Contribution

It reveals the combined effects of interfacial heterogeneous nucleation and oxygen pressure on ReNiO3 thin film growth and electronic properties, providing new strategies for their synthesis.

Findings

Heterogeneous nucleation allows ReNiO3 growth at atmospheric pressure.

High oxygen pressure is required to trigger electronic transitions.

Oxygen vacancies are eliminated at high oxygen pressures, enabling electronic phase changes.

Abstract

Although rare earth nickelates (ReNiO3) exhibit abundant electronic phases and widely adjustable metal to insulator electronic transition properties, their practical electronic applications are largely impeded by their intrinsic meta stability. Apart from elevating oxygen reaction pressures, heterogeneous nucleation is expected as an alternative strategy that enables the crystallization of ReNiO3 at low meta stability. In this work, the respective roles of high oxygen pressure and heterogeneous interface in triggering ReNiO3 thin films growth at metastable state are revealed. The ReNiO3 (Re:Nd, Sm, Eu, Gd, and Dy) heterogeneous thin films growth on LaAlO3 single crystal substrate have an effective crystallization at atmosphere without the necessity to apply high oxygen pressures, suggesting the interfacial bonding between the ReNiO3 and substrates can sufficiently reduce the positive Gibbs formation energy of ReNiO3, which is further verified by the first principles calculations. Nevertheless, the abrupt electronic transitions only appear in ReNiO3 thin films grown at high oxygen pressures, in which cases the oxygen vacancies are effectively eliminated via high oxygen pressure reactions as indicated by near edge X ray absorption fine structure (NEXAFS). This work unveils the synergistic effects of heterogeneous nucleation and high oxygen pressure on the growth of high quality ReNiO3 thin films.