학술논문
浓度梯度掺杂实现BiFeO3薄膜自极化 / Self-polarization Achieved by Compositionally Gradient Doping in BiFeO3 Thin Films
Document Type
Academic Journal
Author
戴乐; 刘洋; 高轩; 王书豪; 宋雅婷; 唐明猛; DMITRY V Karpinsky; 刘丽莎; 汪尧进; DAI Le; LIU Yang; GAO Xuan; WANG Shuhao; SONG Yating; TANG Mingmeng; LIU Lisha; WANG Yaojin
Source
无机材料学报 / Journal of Inorganic Materials. 39(1):99-中插108
Subject
Language
Chinese
ISSN
1000-324X
Abstract
BiFeO3 是一种非常有前途的无铅铁电材料,与大多数传统铁电材料相比,它具有更大的极化和更高的居里温度,为高温应用提供了可能.受到衬底强烈的夹持效应、较大的矫顽场和漏电流的影响,BiFeO3 薄膜难以被极化.自极化是解决这一问题的可行方法.本研究采用溶胶-凝胶法在Pt(111)/Ti/SiO2/Si衬底上生长了BiFeO3 薄膜,向上梯度薄膜(从衬底BiFeO3过渡到薄膜表面Bi0.80Ca0.20FeO2.90)以及向下梯度薄膜(从衬底Bi0.80Ca0.20FeO2.90过渡到薄膜表面BiFeO3).通过细致地调控薄膜内部缺陷的定向分布形成内置电场,从而导致薄膜具有自极化特性.压电力显微镜结果表明:在BiFeO3 薄膜中,Ca的梯度方向可以调控自极化的方向.此外,类似二极管的单向导通特性验证了薄膜的自极化是由Ca的浓度梯度掺杂导致.X射线光电子能谱结果表明,氧空位的梯度分布导致的内置电场可能是造成自极化现象的原因.本研究为实现铁电薄膜的自极化提供了一种新的策略,并在以自极化的内置电场为驱动,提高光伏或光敏器件性能方面具有潜在的应用前景.
BiFeO3 is a highly promising lead-free ferroelectric material,surpassing most conventional ferroelectric materials in terms of the polarization and Curie temperature,offering a pathway for potential applications at elevated temperatures.Nevertheless,challenges arise due to strong clamping effect of substrate,large coercive fields,and high leakage currents,causing BiFeO3 films difficult to be polarized.The implementation of self-polarization presents a viable solution.Herein,we prepared BiFeO3,up-graded films(which transition from BiFeO3 to Bi0.80Ca0.20FeO2.90 from the substrate to the film surface),and down-graded films(which transition from Bi0.80Ca0.20FeO2.90 to BiFeO3 from the substrate to the film surface)using the Sol-Gel method on Pt(111)/Ti/SiO2/Si substrates.After directional distribution of defects within the film being carefully modulated,the BiFeO3 films are self-polarization when induced by build-in electric field.Piezoresponse force microscopy show that the up-graded and down-graded self-polarization behavior can be modulated by gradient direction of Ca in BiFeO3 thin films.Moreover,diode-like current-voltage signature verifies the composition gradient-induced self-polarization.The X-ray photoelectron spectroscopy results indicate that the polarization orientation mechanism may arise from the internal electric field attributed to the gradient distribution of oxygen vacancy.This work provides a new strategy to achieve self-polarization in ferroelectric thin films,as well potential novel application in improving the performance of photovoltaic or photosensitive devices as assisted by internal field via self-aligned ferroelectric polarization.
BiFeO3 is a highly promising lead-free ferroelectric material,surpassing most conventional ferroelectric materials in terms of the polarization and Curie temperature,offering a pathway for potential applications at elevated temperatures.Nevertheless,challenges arise due to strong clamping effect of substrate,large coercive fields,and high leakage currents,causing BiFeO3 films difficult to be polarized.The implementation of self-polarization presents a viable solution.Herein,we prepared BiFeO3,up-graded films(which transition from BiFeO3 to Bi0.80Ca0.20FeO2.90 from the substrate to the film surface),and down-graded films(which transition from Bi0.80Ca0.20FeO2.90 to BiFeO3 from the substrate to the film surface)using the Sol-Gel method on Pt(111)/Ti/SiO2/Si substrates.After directional distribution of defects within the film being carefully modulated,the BiFeO3 films are self-polarization when induced by build-in electric field.Piezoresponse force microscopy show that the up-graded and down-graded self-polarization behavior can be modulated by gradient direction of Ca in BiFeO3 thin films.Moreover,diode-like current-voltage signature verifies the composition gradient-induced self-polarization.The X-ray photoelectron spectroscopy results indicate that the polarization orientation mechanism may arise from the internal electric field attributed to the gradient distribution of oxygen vacancy.This work provides a new strategy to achieve self-polarization in ferroelectric thin films,as well potential novel application in improving the performance of photovoltaic or photosensitive devices as assisted by internal field via self-aligned ferroelectric polarization.