Multiferroic BiFe O3 thin films deposited on SrRu O3 buffer layer by rf sputtering

Abstract

SrRu O3 (SRO) acts as an effective buffer layer for growth of multiferroic BiFe O3 (BFO) thin films deposited on PtTi O2 Si O2 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 PtTi O2 Si O2 Si substrate. A much enlarged remnant polarization (2 Pr) of 144 μC cm2 and a coercive field (Ec) of 386 kVcm were obtained with the BFO thin film deposited on SROPtTi O2 Si O2 Si at 600 °C. The BFO thin film with SRO buffer layer also shows a large nonvolatile polarization (ΔP= Psw - Pnsw) of 122 μC cm2 at 20 μs, which promises excellent performance for random access memories. Further interestingly, it exhibits little polarization fatigue up to 5× 1010 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 (Ms) of 1.92 emu cm3 and coercivity (Hc) of 325 Oe. © 2007 American Institute of Physics.