Determination of the electrostatic potential distribution in Pt/Fe:SrTiO₃/Nb:SrTiO₃ thin-film structures by electron holography.

Astrid Marchewka,Hongchu Du,Rafal E Dunin-Borkowski,Stephan Menzel,David Cooper,Rainer Waser,Regina Dittmann,Christian Lenser

doi:10.1038/srep06975

Abstract

We determined the electrostatic potential distribution in pristine Pt/Fe:SrTiO3/Nb:SrTiO3 structures by electron holography experiments, revealing the existence of a depletion layer extending into the Nb-doped bottom electrode. Simulations of potential profiles in metal-insulator-metal structures were conducted assuming different types and distributions of dopants. It is found that the presence of acceptor-type dopant concentrations at the Fe:SrTiO3/Nb:SrTiO3 interface with a donor-doped insulating layer provides a good match to the measured profile. Such acceptor-type interface concentrations may be associated with Sr vacancies on the Nb:SrTiO3 side of the bottom interface.

Highlights

Correspondence and requests for materials should be addressed to Determination of the electrostatic potential distribution in Pt/Fe:SrTiO3/ Nb:SrTiO3 thin-film structures by electron holography
In the model system consisting of epitaxial SrTiO3 thin films grown on conducting Nb-doped SrTiO3 single crystals that serve as the bottom electrode[12], it is generally assumed that the bottom interface can be regarded as an ohmic contact, with switching taking place at the top interface[13,14]
Off-axis electron holography was used to determine the potential distribution across the Pt/Fe:SrTiO3/Nb:SrTiO3 layer stack

Summary

Introduction

Correspondence and requests for materials should be addressed to Determination of the electrostatic potential distribution in Pt/Fe:SrTiO3/ Nb:SrTiO3 thin-film structures by electron holography. Simulations of potential profiles in metal-insulator-metal structures were conducted assuming different types and distributions of dopants. It is found that the presence of acceptor-type dopant concentrations at the Fe:SrTiO3/Nb:SrTiO3 interface with a donor-doped insulating layer provides a good match to the measured profile. Such acceptor-type interface concentrations may be associated with Sr vacancies on the Nb:SrTiO3 side of the bottom interface. M etal-insulator-metal (MIM) structures based on transition metal oxide thin films have attracted tremendous attention as resistance switching memory cells for next-generation nonvolatile memory applications[1,2,3]. A good match to the experimental potential distribution is provided by introducing acceptor-type dopants at the bottom electrode interface with a donor-doped oxide layer in the simulations. For the application of Pt/ Fe:SrTiO3/Nb:SrTiO3 structures as resistance switching elements, we conclude that the local field distribution may affect the site of oxygen vacancy movement and needs to be taken into account when analysing resistive switching phenomena

Methods

Results

Conclusion