Improving electrical properties of ferroelectric thin films by ultraviolet radiation

Ferroelectric films in the paraelectric phase exhibit two undesirable properties: hysteresis in the voltage-capacitance characteristics and a significant relaxation time of the capacitance. Our experiments show that suppression of both of these is achieved by using ultraviolet (UV) radiation with wavelengths corresponding to the material forbidden gap. Experimentally we also observed UV radiation induced modulation of thin film permittivity without an applied electric field. The observed phenomena are believed to have the same origin: UV light causes generation of non-equilibrium charge carriers and space charge redistribution inside thin ferroelectric films.