Growth and thermal stability of epitaxial BiFeO 3 thin films

Abstract

We have investigated the oxygen pressure and the temperature dependence on BiFeO 3 thin films deposited on SrTiO 3 substrates by pulsed laser deposition. Reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM) and X-ray diffraction measurements indicate that high-quality epitaxial thin films are obtained for P O 2 = 0.4 mbar and T=650 °C. Outside of this pressure–temperature window, parasitic peaks attributed to β-Bi 2O 3 appear. We find an increase of the out-of-plane lattice parameter with oxygen pressure that we ascribe to Bi-deficiency due to its high volatility at low pressure. Ex-situ anneals have been performed and results show that as-grown single-phase BiFeO 3 thin films degrade after annealing, whereas as-grown BiFeO 3 containing impurity phases evolve toward a single-phase structure. These experiments demonstrate that parasitic phases can stabilize compounds which are usually unstable in air at elevated temperatures.