Local Electric Property Modification of Ferroelectric Tunnel Junctions Induced by Variation of Polarization Charge Screening Conditions under Measurement with Scanning Probe Techniques

Natalia Andreeva,Victor Luchinin,Anatoliy Petukhov,Oleg Vilkov,Adrian Petraru

doi:10.3390/nano11123323

Natalia Andreeva, Victor Luchinin + Show 3 more

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https://doi.org/10.3390/nano11123323

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Journal: Nanomaterials	Publication Date: Dec 7, 2021
Citations: 2	License type: CC BY 4.0

Affiliation: St Petersburg University, Kiel University

Abstract

Scanning tunneling spectroscopy in ultrahigh vacuum conditions and conductive atomic-force microscopy in ambient conditions were used to study local electroresistive properties of ferroelectric tunnel junctions SrTiO3/La0.7Sr0.3MnO3/BaTiO3. Interestingly, experimental current-voltage characteristics appear to strongly depend on the measurement technique applied. It was found that screening conditions of the polarization charges at the interface with a top electrode differ for two scanning probe techniques. As a result, asymmetry of the tunnel barrier height for the opposite ferroelectric polarization orientations may be influenced by the method applied to study the local tunnel electroresistance. Our observations are well described by the theory of electroresistance in ferroelectric tunnel junctions. Based on this, we reveal the main factors that influence the polarization-driven local resistive properties of the device under study. Additionally, we propose an approach to enhance asymmetry of ferroelectric tunnel junctions during measurement. While keeping the high locality of scanning probe techniques, it helps to increase the difference in the value of tunnel electroresistance for the opposite polarization orientations.

Highlights

Ferroelectric tunnel junctions (FTJs) are considered as non-volatile memory cells with a non-destructive read-out process, ultra-low power consumption, and high storage density.They can provide a promising solution for an electronic analogue of a synapse for further implementation in neuromorphic systems
For measurements of tunnel electroresistance (TER) ratio, induced by polarization switching in thin BTO films, we first consider the FTJs with a gold top electrode and atomic force microscopy (AFM) probe placed on it (Figure 2a)
Polarization charges at the interfaces with electrodes are compensated by screening charges in electrodes distributed over the electronic screening length

Summary

Introduction

Ferroelectric tunnel junctions (FTJs) are considered as non-volatile memory cells with a non-destructive read-out process, ultra-low power consumption, and high storage density. They can provide a promising solution for an electronic analogue of a synapse for further implementation in neuromorphic systems. In FTJs, two dissimilar electrodes are separated by a thin ferroelectric (FE) film [1,2], the polarization state of which controls the tunnel electroresistance (TER) of the structure. If the top and bottom electrodes are made of different materials, arising asymmetry of the junction changes screening conditions of the polarization charge at the electrode/FE film interfaces.

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