  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.
