Domain switching kinetics in ferroelectric-resistive BiFeO3 thin film memories. (19th January 2015)

• Record Type: Journal Article
• Authors: Meng, Jianwei; Jiang, Jun; Geng, Wenping; Chen, Zhihui; Zhang, Wei; Jiang, Anquan
• Is Part Of: Japanese journal of applied physics. Volume 54:Number 2(2015:Jan.)Supplement
• Publication Date: 2015-01-19
• Subjects: Physics -- Periodicals; 621.05
• DOI: 10.7567/JJAP.54.024102
• Languages: English
• ISSNs: 0021-4922

Abstract

Abstract: We fabricated (00 l ) BiFeO3 (BFO) thin films in different growth modes on SrRuO3 /SrTiO3 substrates using a pulsed laser deposition technique. X-ray diffraction patterns show an out-of-plane lattice constant of 4.03 Å and ferroelectric polarization of 82 µC/cm 2 for the BFO thin film in a layer-by-layer growth mode (2D-BFO), larger than 3.96 Å and 51 µC/cm 2 for the thin film in the 3D-island formation growth mode (3D-BFO). The 2D-BFO thin film at 300 K shows switchable on/off diode currents upon polarization flipping near a negative coercive voltage, which is nevertheless absent from the above 3D-BFO thin film. From a positive-up–negative-down pulse characterization technique, we measured domain switching current transients as well as polarization–voltage ( P f – V f ) hysteresis loops in both semiconducting thin films. P f – V f hysteresis loops after 1 µs-retention time show the preferred domain orientation pointing to bottom electrodes in a 3D-BFO thin film. The poor retention of the domains pointing to top electrodes can be improved considerably in a 2D-BFO thin film. From these measurements, we extracted domain switching time dependence of coercive voltage at temperatures of 78–300 K. From these dependences, we found coercive voltages in semiconducting ferroelectric thin films much higher than those in insulating thin films, disobeying the traditional Merz equation. Finally, an equivalent resistance model in description of free-carrier compensation of the front domain boundary charge is developed to interpret this difference. This equivalent resistance can be coincidently extracted either from domain switching time dependence of coercive voltage or from applied voltage dependence of domain switching current, which drops almost linearly with the temperature until down to 0 in a ferroelectric insulator at 78 K.