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.