Epitaxial Fe3O4 Films Grown on R-Plane Sapphire by Pulsed Laser Deposition

Abstract

We have studied the influence of growth temperature and molecular oxygen pressure on the properties of thin (≤180 nm) epitaxial magnetite (Fe3O4) (001) films grown by pulsed laser deposition on R-plane single-crystal sapphire (Al2O3 ($$\bar {1}$$012)) with and without MgO seed layer. The electrical, morphological, and structural characteristics of the films have been investigated as functions of growth conditions. Fe3O4 has been shown to have a stable growth plateau at pressures in the range (4–9) × 10–5 Torr. The properties of the epitaxial Fe3O4 films grown on a MgO seed layer (5 nm thick) approach those of magnetite films grown on single-crystal MgO substrates and are superior to those of films grown on pure R-plane sapphire. The best electrical characteristic of the films and the corresponding crystal structure can be obtained at elevated growth temperatures, whereas reduced growth temperatures minimize the roughness of their surface and maximize its homogeneity. These conditions can be reconciled by high-temperature high-vacuum annealing of magnetite films grown at reduced temperatures.