Effect of Substrate Material on Growth of Bi-Fe-Oxide Films by Reactive Ion Beam Sputtering

Non-thermoequilibrium Bi 3 Fe 5 O 12 garnet can be obtained by direct epitaxial growth onto a single-crystal garnet substrate from the vapor phase. Using a reactive ion beam sputtering technique and a target composed of 3Bi 2 O 3 and 5Fe 2 O 3 (molar ratio), variations in the crystalline phase with the substrate material were investigated for a variety of substrates. The substrate materials employed were fused quartz, sintered alumina, and single crystals of MgO, SrTiO 3 , MgAl 2 O 4 and Gd 3 (ScGa) 5 O 12 ; films were prepared with these substrates at room temperature, at 480°C and at 540°C. The garnet phase did not appear on substrates other than single-crystal garnet. The thermoequilibrium phases BiFeO 3 and Bi 2 Fe 4 O 9 were formed only on alumina substrate. A new non-thermoequilibrium oxide with a Bi:Fe molar ratio of 3:5 was formed on the fused quartz, MgO, SrTi0 3 and MgAl 2 O 4 substrates by crystallization during deposition. The oxide was found to be antiferromagnetic at room temperature.