外延铁酸铋薄膜铁电性和反转特性的研究

Ferroelectricity and Reverse Properties of Epitaxial BiFeO_3 Thin Films

采用磁控溅射的方法在以SrRuO3(SRO)为底电极的(001)取向的SrTiO3基片上制备了外延BiFeO3(BFO)薄膜,并以氧化铟锡(ITO)和金属Pt为上电极构架了ITO/BFO/SRO和Pt/BFO/SRO两种薄膜电容器,研究上电极对外延BFO薄膜铁电性和反转特性的影响。结果表明,两种薄膜电容器均体现了良好的饱和电滞回线,当测试电场为333kV/cm时,ITO/BFO/SRO和Pt/BFO/SRO两种电容器的剩余极化强度分别为47.6μC/cm2和56μC/cm2,矫顽场分别为223kV/cm和200kV/cm。此外,两种薄膜电容器都具有良好的保持和抗疲劳特性。通过反转和非反转电流对时间的积分,可以计算出真实的极化强度。当反转电压幅值为17V时,ITO/BFO/SRO和Pt/BFO/SRO两种电容器电流的反转时间分别为0.48μs和0.32μs,真实极化强度的计算值约为41μC/cm2和47μC/cm2,此计算值和铁电净极化强度的测量值符合的很好。

In order to investigate impacts of top electrodes on ferroelectricity and reverse properties of typical BFO capacitors,epitaxial BiFeO3（ BFO） thin films were grown on（ 001）-oriented SrRuO3/SrTiO3（ SRO/STO） heterojunction by magnetron sputtering to fabricate ITO/BFO/SRO and Pt/BFO/SRO capacitors. The well saturated electrical hysteresis loops of ITO / BFO / SRO and Pt / BFO / SRO capacitors possess remanent polarizations of 47. 6 μC / cm2 and 56 μC / cm2,measured at 333 k V/cm,respectively. The coercive fields are 223 k V / cm and 200 k V / cm,respectively. Retention and fatigue tests prove that both BFO thin film capacitors have an ability of maintaining a written logic and resistance to fatigue. Moreover,reversed and non-reversed current responses were measured,from which the reversed time of ferroelectric domains of ITO / BFO / SRO and Pt / BFO / SRO capacitors are 0. 48 μs and 0.32 μs,respectively. The contributed polarizations of ITO / BFO / SRO and Pt / BFO / SRO capacitors are calculated to be 41 μC / cm2 and 47 μC / cm2 at the applied bias of 17 V in amplitude,which are consistent with that obtained from the ferroelectric pulse polarization ΔP measurement.