Selective growth of Fe3O4 and γ-Fe2O3 films with reactive magnetron sputtering

A selective method for growing high-quality spinel-type epitaxial Fe3O4(0 0 1) or gamma-Fe2O3(0 0 1) films was developed using conventional planar-type sputtering by controlling the flow rate of oxygen gas (phi(O2)). Although magnetization of the oxide films is close to that of Fe3O4 or gamma-Fe2O3 for all phi(O2), the room-temperature resistivity and the Fe3+ and Fe2.5+ composition ratios of the films are dependent on phi(O2). The films for 0.2 <= phi(O2) <= 0.5 sccm and phi(O2) >= 0.7 sccm are identified as Fe3O4 and gamma-Fe2O3 films, respectively. All the results suggest that Fe2O3 films are obtained only when sputtered in the metal mode, and gamma-Fe2O3 films are obtained in the oxide mode.