Influence of the ferroelectric polarization on the electronic structure of BaTiO3 thin films

TL;DR

This study investigates how ferroelectric polarization affects the electronic structure of BaTiO3 thin films, revealing polarization-dependent shifts and surface effects using advanced microscopy and spectroscopy techniques.

Contribution

It demonstrates the direct influence of ferroelectric polarization on electronic levels and surface properties in BaTiO3 thin films, with detailed experimental analysis.

Findings

Polarization induces up to 300 meV shifts in work function.

Surface termination is Ba-O with polarization-dependent surface adsorption.

Electrostatic models are insufficient to explain electronic modifications.

Abstract

Micrometric domains of precise ferroelectric polarization have been written into a 20 nm thick epitaxial thin film of BaTiO3(001) (BTO) on a Nb doped SrTiO3 (STO) substrate using PiezoForce Microscopy (PFM). The domain dependent electronic structure has been studied using fully energy-filtered PhotoEmission Microscopy (PEEM) and synchrotron radiation. Shifts, induced by ferroelectric polarization, of up to 300 meV are observed in the work function of the sample. The surface is Ba-O terminated. Polarization-induced distortion of the electronic structure is observed in the valence band and on the Ba 3d, Ti 2p and O 1s core levels of BTO. Polarization dependent surface adsorption is observed. A simple electrostatic model based on net surface charge is not sufficient to explain the observed modifications in the electronic levels.