| HUO Xing-min,ZHANG Xian-gui,LIU Li-fang,HOU Zhi-qing,ZHAO Bin,WANG Yun-ming,WEI Dong-rui,DONG Lei,ZENG Hao-yu,SONG Jian-min.#$NP Structure and Ferroelectric Photovoltaic Properties of Epitaxial BiFeO3 Thin Films on MgO Substrate[J],52(6):377-383 |
| #$NP Structure and Ferroelectric Photovoltaic Properties of Epitaxial BiFeO3 Thin Films on MgO Substrate |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.06.034 |
| KeyWord:epitaxial films BiFeO3 magnetron sputtering ferroelectric photovoltaic |
| Author | Institution |
| HUO Xing-min |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
| ZHANG Xian-gui |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
| LIU Li-fang |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
| HOU Zhi-qing |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
| ZHAO Bin |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
| WANG Yun-ming |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
| WEI Dong-rui |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
| DONG Lei |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
| ZENG Hao-yu |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
| SONG Jian-min |
School of Science, Hebei Agricultural University, Hebei Baoding , China |
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| Abstract: |
| Bismuth ferrite BiFeO3 (BFO), a multiferroic material with both ferroelectric and antiferromagnetic properties, has great potential in ferroelectric photovoltaic applications due to its large residual polarization (~100 μC/cm2), high Curie temperature (~810 ℃) and suitable band gap (~ 2.7 eV). In particular, the thin film structure has more excellent photoelectric conversion efficiency than single crystal and ceramics. In order to deeply investigate crystalline structure, growth orientation, and effect of test temperature on the dielectric and ferroelectric photovoltaic properties of BFO thin films, the Pt/BFO/La0.5Sr0.5CoO3(LSCO)/MgO heterostructure ferroelectric capacitor was fabricated by employing off-axis magnetron sputtering, in which the single crystal (001) MgO and epitaxial LSCO film were used as substrates and bottom electrodes, respectively. Some important results were obtained as follows. Firstly, the X-ray diffraction (XRD) and Phi scanning results indicated that the MgO based BFO and LSCO films were not only both good crystallized perovskite structure, but also (00l) epitaxial relationships with MgO substrate. Secondly, when tested at different voltages and frequencies, the BFO ferroelectric film exhibited a stronger ferroelectric property, in which the positive and negative coercive voltages were about 3.36 V and –1.12 V, respectively. However, a obvious dielectric dispersion phenomenon was also observed, namely, dielectric loss had a minimum value of 0.016 at ~100 kHz and increased to 0.212 at 8 MHz, which was mainly due to the relaxation competition mechanism of various types of charges in BFO ferroelectric film. Thirdly, under a vertical 250 mW/cm2 purple light at room temperature (20 ℃), the photovoltaic performances revealed that the open circuit voltage (VOC) and short circuit current (JSC) were about 0.32 V and 0.21 mA/cm2, respectively. By further increasing test temperatures from 40 °C to 100 °C with an interval of 20 ℃ (40, 60, 80 and 100 ℃), it was found that the values of VOC decreased slowly and then rapidly, while the amplitudes of JSC increased rapidly and then decreased. At a critical temperature of 80 ℃, the BFO ferroelectric film exhibited a faster photovoltaic response speed, in which the values of VOC and JSC were about 0.30 V and 0.96 mA/cm2, respectively. Finally, the energy band analysis was also conducted to study photovoltaic mechanism in BFO ferroelectric film. It was found that a large work function difference (~1 eV) between the bottom electrode LSCO and the top electrode Pt film resulted in a strong built-in electric field in the BFO film, which was beneficial to the separation of photo-generated carriers, thereby greatly improving the BFO ferroelectric photovoltaic effect of thin films. In all, this study not only shows that BFO is an excellent and environmentally friendly photovoltaic candidate material with great potential application value, and also provides a practical strategy for improving the performance of BFO ferroelectric photovoltaic devices. |
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