Interface Electronic Structure in a Metal/Ferroelectric Heterostructure under Applied Bias

TL;DR

This study investigates how the electronic structure at the interface of a metal/ferroelectric heterostructure changes under applied bias, revealing the influence of interface chemistry and polarization on barrier heights using X-ray photoelectron spectroscopy.

Contribution

It provides the first in-situ measurement of band alignment and barrier height variations in a prototypical metal/ferroelectric heterostructure under bias.

Findings

Barrier heights depend on interface chemistry and ferroelectric polarization.

Core level shifts vary with applied bias and polarization state.

Band alignment measurements support transport data.

Abstract

The effective barrier height between an electrode and a ferroelectric (FE) depends on both macroscopic electrical properties and microscopic chemical and electronic structure. The behavior of a prototypical electrode/FE/electrode structure, Pt/BaTiO3/Nb-doped SrTiO3, under in-situ bias voltage is investigated using X-Ray Photoelectron Spectroscopy. The full band alignment is measured and is supported by transport measurements. Barrier heights depend on interface chemistry and on the FE polarization. A differential response of the core levels to applied bias as a function of the polarization state is observed, consistent with Callen charge variations near the interface.