Charge redistribution at metal-ZrO2 interfaces: A combined DFT and continuum electrostatic study

TL;DR

This study combines DFT and continuum models to analyze charge redistribution at metal-ZrO2 interfaces, revealing short- and long-range effects that influence charge transport and oxide growth.

Contribution

It introduces a coupled DFT and continuum approach to quantify charge redistribution at metal-ZrO2 interfaces, highlighting the roles of doping and metal type.

Findings

Short-range charge redistribution confined to a few atomic layers.

Long-range space charge extends over hundreds of nanometers depending on doping.

Schottky barrier height depends more on metal work function than doping level.

Abstract

Nanoscale metallic inclusions (NMIs) are commonly observed within oxide scales formed during high-temperature oxidation, revealing the existence of chemical and electronic heterogeneity beyond conventional corrosion theories that assume homogeneous, fully oxidized films. Using tetragonal zirconia (tZrO2) facing a series of face-centered cubic (fcc) metals as the model system, this work investigates the short-range and long-range charge redistributions across metal-oxide interfaces by coupling density functional theory (DFT) calculations with continuum modeling. We show that metal-oxide contact induces a short-range charge redistribution confined to a few atomic layers and a long-range redistribution of space charge that can extend over macroscopic distances within weakly doped oxides. DFT calculations show that the short-range redistribution is dominated by metal induced gap states (MIGS) in tZrO2 facing noble metals like Au and Ag, and by chemical bonding in tZrO2 facing active metals like Al. DFT-informed continuum theoretical analysis shows that the range of space-charge redistribution is governed by the doping level of tZrO2, and that the Schottky barrier height (SBH) exhibits a stronger dependence on the metal work function than the doping level. Both the short-range and long-range charge redistributions can alter the transport of charge carriers via their associated electric fields, extending several nm to hundreds of nm from the interface, depending on the doping concentrations, suggesting possible heterogeneous oxide growth caused by NMIs.