Phase Change Observed in Ultrathin Ba0.5Sr0.5TiO3 Films by in-situ Resonant Photoemission Spectroscopy

TL;DR

This study investigates phase change phenomena in ultrathin Ba0.5Sr0.5TiO3 films using in-situ resonant photoemission spectroscopy, revealing a critical thickness range where structural properties abruptly change due to size effects.

Contribution

It identifies a critical thickness range for phase change in ultrathin Ba0.5Sr0.5TiO3 films using in-situ spectroscopy, highlighting size effects on phase stability.

Findings

Abrupt spectral variation between 2.0 nm and 2.8 nm films

Critical thickness for phase change estimated between 2.0 nm and 2.8 nm

Size effects likely cause the observed phase transition

Abstract

Epitaxial Ba0.5Sr0.5TiO3 thin films were prepared on Nb-doped SrTiO3 (100)substrates by the pulsed laser deposition technique, and were studied by measuring the Ti 2p - 3d resonant photoemission spectra in the valence-band region as a function of film thickness, both at room temperature and low temperature. Our results demonstrated an abrupt variation in the spectral structures between 2.8 nm (~7 monolayers) and 2.0 nm (~5 monolayers) Ba0.5Sr0.5TiO3 films, suggesting that there exists a critical thickness for phase change in the range of 2.0 nm to 2.8 nm. This may be ascribed mainly to the intrinsic size effects.