偏置电场调控BiFeO3铁电薄膜材料光电效应研究

Photoelectric effect of ferroelectric films has attracted extensive attention. Especially, about 6.0% light-to-electric energy conversion and 16.0 volt open circuit voltage are obtained in epitaxial ferroelectric films, which suggested that ferroelectric materials are suitable for solar cell and light-sensor applications. The exchange bias phenomenon, named as a shift along the magnetic field axis in the hysteresis loop of ferromagnetic/antiferromagnetic thin films, has been tremendously applied in spin valves and magnetic tunnel junction structures for magnetic recording and sensors. In this preoject, the internal electric field bias, named as voltage shift along the voltage axis in the hysteresis behaviors of ferroelectric thin films has been considered for studying the photoelectric effect. It is believed that the internal electric field bias can be tuned by the depolarization field, the strain gradient, the oxygen vacancies, and the interface layers in BiFeO3 thin films. A mode is proposed to explain the fact that the photoelectric effect can be tuned by the internal electric field bias. These results are important for ferroelectric-based energy conversion and sensor applications.

近年来铁电材料光电效应研究引起了广泛关注。在外延铁电薄膜中分别获得了高达6.0%的光电转换效率和16.0伏特的开路电压，显示出铁电材料在新型太阳能及光电探测的广阔应用前景。在铁磁/反铁磁体系中，界面处交换偏置现象被利用来制备自旋阀和磁隧道结等结构，应用于磁存储器、磁传感等磁电子学器件。考虑到铁电与铁磁材料的相似性，在本项目中，我们将铁电材料电滞回线沿电压轴偏移的偏置电场应用于铁电材料光电效应研究。选择BiFeO3铁电薄膜为研究体系，拟从退极化场、应力梯度、氧缺陷及界面层等多个方面来调节偏置电场，深入认识影响偏置电场的关键因素，探索偏置电场调控BiFeO3薄膜光电效应的内在物理机制。通过改变BiFeO3薄膜中的偏置电场来调节分离光生载流子分离驱动力，提高其光电效应。这将增强铁电材料在能量转换及光电传感器等方面应用，具有重要意义。

近年来铁电材料光电效应研究显示出铁电材料在新型太阳能及光电探测的广阔应用前景。在铁磁/反铁磁体系中，界面处交换偏置现象被利用来制备自旋阀和磁隧道结等结构，应用于磁存储器、磁传感等磁电子学器件。考虑到铁电与铁磁材料的相似性， 在本项目中，我们将铁电材料电滞回线沿电压轴偏移的偏置电场应用于铁电材料光电效应研究。在BiFeO3和Pb(ZrTi)O3 等铁电薄膜中,研究了退极化场、应力梯度、氧缺陷及界面层等多个方面对偏置电场的调节机制，获得了偏置电场调控BiFeO3等铁电薄膜光电效应的内在物理机制。通过本研究，掌握了影响铁电薄膜偏置电场的主要因素，理解了偏置电场提高光电效应的基本物理机制。