DIELECTRIC-RELAXATION OF (BA,SR)TIO3 THIN-FILMS

The dielectric relaxation of (Ba0.5Sr0.5)TiO3 thin films with high electric resistivity is investigated. The films are deposited by an rf-magnetron sputtering method in an atmosphere of argon and oxygen. The dielectric dispersion of the films is measured in the frequency range of 10(-2)-10(6) Hz. It is found that the dielectric constant epsilon slightly decreases with frequency, following the relationship of d epsilon/d(log(10)f)similar to-0.01 epsilon, and the dielecltric loss is almost constant at less than 1% in the measured frequency range. This type of dielectric relaxation causes absorption current which is inversely proportional to time, as the result of the dielectric aftereffect. In a dynamic random access memory (DRAM) operation, the dielectric relaxation would result in less than 10% loss of storage charge during the refresh cycle, and the film's DC leakage less affects the device operation.