Sr-doping effects on conductivity, charge transport, and ferroelectricity of Ba0.7La0.3TiO3 epitaxial thin films
Qiang Li(李强)1, 2, Dao Wang(王岛)1, 2, Yan Zhang(张岩)1,2, Yu-Shan Li(李育珊)1, 2, Ai-Hua Zhang(张爱华)1,2,†, Rui-Qiang Tao(陶瑞强)1, 2, Zhen Fan(樊贞)1, 2, Min Zeng(曾敏)1, 2, Guo-Fu Zhou(周国富)2, 3, Xu-Bing Lu(陆旭兵)1, 2,‡, and Jun-Ming Liu(刘俊明)1, 4
1 Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; 2 Guangdong Provincial Key Laboratory of Optical Information Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; 3 National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou 510006, China; 4 Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210009, China
Abstract Sr-doped Ba0.7La0.3TiO3 (BSLTO) thin films are deposited by pulsed laser deposition, and their microstructure, conductivity, carrier transport mechanism, and ferroelectricity are systematically investigated. The x-ray diffraction measurements demonstrate that Sr-doping reduces the lattice constant of BSLTO thin films, resulting in the enhanced phonon energy in the films as evidenced by the Raman measurements. Resistivity-temperature and Hall effect measurements demonstrate that Sr can gradually reduce electrical resistivity while the electron concentration remains almost unchanged at high temperatures. For the films with semiconducting behavior, the charge transport model transforms from variable range hopping to small polaron hopping as the measurement temperature increases. The metalic conductive behaviors in the films with Sr=0.30, 0.40 conform to thermal phonon scattering mode. The difference in charge transport behavior dependent on the A-site cation doping, is clarified. It is revealed that the increasing of phonon energy by Sr doping is responsible for lower activation energy of small polaron hopping, higher carrier mobility, and lower electrical resistivity. Interestingly, the piezoelectric force microscopy (PFM) results demonstrate that all the BSLTO films can exhibit ferroelectricity, especially for the room temperature metallic conduction film with Sr=0.40. These results imply that Sr-doping could be a potential way to explore ferroelectric metal materials for other perovskite oxides.
Received: 12 August 2020
Revised: 30 September 2020
Accepted manuscript online: 15 October 2020
PACS:
77.55.fe
(BaTiO3-based films)
Fund: Project supported by the National Natural Science Foundation of China (Grant No. 51872099), the Science and Technology Program of Guangzhou, China (Grant No. 2019050001), the Fund from the Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, China (Grant No. 2017B030301007), and the 111 Project, China. Xu-Bing Lu, one of authors, was sponsored by the Project for Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme, China (2016).
Qiang Li(李强), Dao Wang(王岛), Yan Zhang(张岩), Yu-Shan Li(李育珊), Ai-Hua Zhang(张爱华), Rui-Qiang Tao(陶瑞强), Zhen Fan(樊贞), Min Zeng(曾敏), Guo-Fu Zhou(周国富), Xu-Bing Lu(陆旭兵), and Jun-Ming Liu(刘俊明) Sr-doping effects on conductivity, charge transport, and ferroelectricity of Ba0.7La0.3TiO3 epitaxial thin films 2021 Chin. Phys. B 30 027701
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