界面退火对外延BiFeO_3薄膜光伏特性的影响

Effect of Annealing on Interface on Photovoltaic Effect of Epitaxial BiFeO_3 Thin Film Capacitor

采用射频磁控溅射的方法在(001)取向的SrRuO_3(SRO)/SrTiO_3(STO)衬底上制备了外延BiFeO_3(BFO)薄膜,在室温条件下溅射一层金属Pt作为上电极,构建了Pt/BFO/SRO电容器。X射线衍射显示BFO薄膜呈现良好的外延生长,极化-电场滞后回线和净极化强度测试结果说明Pt/BFO/SRO电容器具有良好的铁电性。为了检测界面对Pt/BFO/SRO电容器光伏特性的影响,将整个Pt/BFO/SRO电容器分别在180℃和500℃的条件下快速热处理2min,以改变Pt/BFO界面态。在室温、180℃和500℃的条件下,Pt/BFO/SRO电容器光伏效应的开路电压分别为0.22V、0.12V和0.05V,短路电流密度分别为9.2μA/cm^2,4.9μA/cm^2和0.12μA/cm^2。开路电压和短路电流密度都随着退火温度的升高而降低,这是高温退火恶化了界面态的结果。在室温条件下,Pt/BFO/SRO电容器光伏效应的光电转换效率为0.009 4%,大于部分前期报道的结果。

Epitaxial BiFeO3(BFO)film was deposited on SrRuO3(SRO)buffered(001)-oriented SrTiO3(STO)substrate using radio frequency magnetron sputtering.Pt dots were grown at room temperature(RT)on epitaxial BFO film as top electrode to form Pt/BFO/SRO capacitor.X-ray diffraction proves to be good epitaxial growth of BFO film.The measurement of polarizationelectric field hysteresis loops and real polarization reveals good ferroelectric properties of Pt/BFO/SRO capacitor.In order to measure the effect of interface state on photovoltaic effect of Pt/BFO/SRO capacitor,the whole Pt/BFO/SRO capacitor is annealed at 180℃and 500℃,respectively.The open circuit voltage of photovoltaic effect for Pt/BFO/SRO capacitor is 0.22 V,0.12 Vand 0.05 Vat RT,180℃and 500℃,respectively.The short circuit current density of photovoltaic effect for Pt/BFO/SRO capacitor is 9.2μA/cm2,4.9μA/cm2 and 0.12μA/cm2 at RT,180℃ and 500 ℃,respectively.Both the open circuit voltage and short circuit density decrease with the increasing annealing temperature,which can be account for the deteriorated interface state between Pt/BFO.The photoelectric conversion efficiency of photovoltaic effect at RT for Pt/BFO/SRO capacitor is 0.009 4%,which is larger than some results in the previous reports.