Selective growth of epitaxial Sr2IrO4 by controlling plume dimensions in pulsed laser deposition

TL;DR

This study demonstrates that controlling plume dimensions and deposition rate in pulsed laser deposition enables the selective growth of pure Sr2IrO4 epitaxial thin films, overcoming phase competition in layered iridates.

Contribution

It introduces a method to stabilize pure Sr2IrO4 phase thin films by reducing plume size and deposition rate in PLD, which was previously challenging due to phase competition.

Findings

Reduced plume dimensions stabilize pure Sr2IrO4 phase.

Slow deposition favors thermodynamically stable interfaces.

Real-time optical spectra monitor phase purity effectively.

Abstract

We report that epitaxial Sr2IrO4 thin-films can be selectively grown using pulsed laser deposition (PLD). Due to the competition between the Ruddlesden-Popper phases of strontium iridates (Sr_{n+1}Ir_{n}O_{3n+1}), conventional PLD methods often result in mixed phases of Sr2IrO4 (n = 1), Sr3Ir2O7 (n = 2), and SrIrO3 (n = infinity). We have discovered that reduced PLD plume dimensions and slow deposition rates are the key for stabilizing pure Sr2IrO4 phase thin-films, identified by real-time in-situ monitoring of their optical spectra. The slow film deposition results in a thermodynamically stable TiO2\\SrO\IrO2\SrO\SrO configuration at an interface rather than TiO2\\SrO\SrO\IrO2\SrO between a TiO2-teminated SrTiO3 substrate and a Sr2IrO4 thin film, which is consistent with other layered oxides grown by molecular beam epitaxy. Our approach provides an effective method for using PLD to achieve pure phase thin-films of layered materials that are susceptible to several energetically competing phases.