Structural and dielectric properties of LuFe2O4 thin films grown by pulsed-laser deposition

Epitaxial LuFe2O4 thin films are deposited on sapphire substrate by pulsed-laser deposition. Different growth conditions are tackled and it is found that substrate temperature is the most critical condition for the film growth; while below 750 °C the film crystallization is poor. The Lu:Fe ratio is also found to be important in forming the LuFe2O4 phase in the films; while higher content of Fe oxide than that of stoichiometric LuFe2O4 in the target is favorable for the formation of the LuFe2O4 phase. However, impurity phases such as Fe3O4 and Fe2O3 are induced in the film with a Fe oxide enriched target. A large dielectric tunability under electric field is revealed in the film; while the dielectric tunability decreases as the frequency increases, and eventually the dielectric tunability disappears above 500 MHz.