Nanoscale Mapping of Potential Barrier Degradation at BaTiO3–Ni Interfaces

Alessio Morelli,Garry Mclaughlin,John Anthony Byrne,Patrick Lemoine,Maureen Strawhorne

doi:10.1021/acsaelm.1c00852

Abstract

Scanning Kelvin probe microscopy was used to investigate the evolution of the Ni–BaTiO3 interfacial potential barriers in multilayer ceramic capacitors degraded by the highly accelerated life test method. We detect electric field discontinuities at such interfaces, which through analysis of the expected band diagrams, are associated with the presence of Schottky barriers. The decrease of discontinuities at the cathode in degraded capacitors denotes barrier lowering, indicative of a transition from Schottky to Ohmic contact, validating the proposed mechanism of oxygen vacancies electromigration being at the origin of insulation resistance degradation. Extrapolation of the depletion layer width is consistent with previous observations, and the possibility toward the use of this technique to obtain quantitative information is discussed.

Highlights

Among the many applications based on ferroelectric oxides, multilayer ceramic capacitors (MLCCs) are used in most electronic devices.[1−3] Being constructed of interdigitated metal electrodes in a matrix of dielectric material, most commonly conductive nickel and high-k ceramic barium titanate (BTO) are employed.[3]
Morphology and compositional details of the polished MLCCs obtained by SEM (Figure 1) confirm BTO dielectric layers and Ni electrodes with thicknesses of about 3.8 and 1.2 μm, respectively
Evolution of potential barriers at the interfaces of degrading Ni−BTO MLCCs is investigated by Kelvin probe force microscopy (KPFM)

Summary

Introduction

Among the many applications based on ferroelectric oxides, multilayer ceramic capacitors (MLCCs) are used in most electronic devices.[1−3] Being constructed of interdigitated metal electrodes in a matrix of dielectric material, most commonly conductive nickel and high-k ceramic barium titanate (BTO) are employed.[3]. In MLCCs the oxygen vacancies in the dielectric BTO layers under a DC electric field accumulate at grain boundaries and metal−oxide interfaces,[5,8] eventually causing component failure by insulation resistance degradation

Methods

Results

Conclusion