Multiferroic BiFeO3 thin films deposited on SrRuO3 buffer layer by rf sputtering

SrRuO3 (SRO) acts as an effective buffer layer for growth of multiferroic BiFeO3 (BFO) thin films deposited on Pt/TiO2/SiO2/Si substrates by radio frequency sputtering. Phase identification by using x-ray diffraction and texture studies by using atomic force microscopy show that the SRO buffer layer promotes crystallization and formation of the perovskite phase at lowered temperature. It significantly reduces the leakage current of multiferroic BFO films, giving rise to a much improved square ferroelectric hysteresis loop, in contrast to the poor loop for BFO on bare Pt/TiO2/SiO2/Si substrate. A much enlarged remnant polarization (2P(r)) of 144 mu C/cm(2) and a coercive field (E-c) of 386 kV/cm were obtained with the BFO thin film deposited on SRO/Pt/TiO2/SiO2/Si at 600 degrees C. The BFO thin film with SRO buffer layer also shows a large nonvolatile polarization (Delta P=P-sw-P-nsw) of 122 mu C/cm(2) at 20 mu s, which promises excellent performance for random access memories. Further interestingly, it exhibits little polarization fatigue up to 5x10(10) switching cycles, at a relatively high voltage of 10 V, although a notable degradation of polarization is shown at the low voltage of 6 V, indicating weak domain pinning. The multiferroic thin film demonstrates a weak ferromagnetic loop with a saturation magnetization (M-s) of 1.92 emu/cm(3) and coercivity (H-c) of 325 Oe. (c) 2007 American Institute of Physics.