Pyroelectric and photovoltaic properties of Nb-doped PZT thin films

A Berenov,J Phair,P Petrov,L Allers,B Moffat,R W Whatmore

doi:10.1063/5.0039593

A Berenov, J Phair + Show 4 more

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https://doi.org/10.1063/5.0039593

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Journal: APL materials	Publication Date: Apr 1, 2021
Citations: 18	License type: cc-by

Affiliation: Imperial College London, Heriot-Watt University

Abstract

Nb-doped lead zirconate titanate (PZT) films with up to 12 at. % of Nb were co-sputtered from oxide PZT and metallic Nb targets at a substrate temperature of 600 °C. Up to 4 at. % of Nb was doped into the perovskite structure with the formation of B-site cation vacancies for charge compensation. The preferential (111) PZT orientation decreased with Nb-doping within the solid solution region. The ferroelectric response of the films was affected by the large values of the internal field present in the samples (e.g., −84.3 kV cm−1 in 12 at. % Nd doped films). As-deposited unpoled films showed large values of the pyroelectric coefficient due to self-poling. The pyroelectric coefficient increased with Nb-doping and showed a complex dependence on the applied bias. The photovoltaic effect was observed in the films. The value of the photocurrent increased with the A/B ratio. The combined photovoltaic–pyroelectric effect increased the values of the measured current by up to 47% upon light illumination.

Highlights

Ba(Mg1/3Nb2/3)O3 buffer layer was deposited on a Pt electrode in sol–gel PZT52/48 films.[43] The internal field observed in PZT45/55 thin films grown by sol–gel and sputtering was related to the Schottky barrier at the bottom Pt–PZT interface.[48] The presence of negative Pb vacancies close to the top electrode was suggested as the origin of the polarity dependence in the dielectric constant in PZT40/60 sol–gel films.[21] In this study, the film growth conditions (including the film thickness) and electrode fabrication techniques were similar for all films and were unlikely to cause systematic changes in the stresses and/or asymmetry of the Schottky barriers
Lead zirconate titanate (PZT) perovskites with the general formula Pb(ZrxTix−1)O3, PZTx/(1 − x), are used extensively in a variety of device applications, such as piezoelectrics and pyroelectrics.Enhanced piezoelectric properties are observed in the compositions close to the morphotropic phase boundary (MPB) at x = 0.53, where rhombohedral and tetragonal phases coexist
The internal field observed in PZT45/55 thin films grown by sol–gel and sputtering was related to the Schottky barrier at the bottom Pt–PZT interface.[48]

Summary

Introduction

Ba(Mg1/3Nb2/3)O3 buffer layer was deposited on a Pt electrode in sol–gel PZT52/48 films.[43] The internal field observed in PZT45/55 thin films grown by sol–gel and sputtering was related to the Schottky barrier at the bottom Pt–PZT interface.[48] The presence of negative Pb vacancies close to the top electrode was suggested as the origin of the polarity dependence in the dielectric constant in PZT40/60 sol–gel films.[21] In this study, the film growth conditions (including the film thickness) and electrode fabrication techniques were similar for all films and were unlikely to cause systematic changes in the stresses and/or asymmetry of the Schottky barriers.

Results

Conclusion