Dielectric Relaxation of (Ba, Sr)TiO₃ Thin Films

Abstract

The dielectric relaxation of (Ba 0.5 Sr 0.5 )TiO 3 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 ε slightly decreases with frequency, following the relationship of d ε /d(log 10 f )∼-0.01 ε , and the dielectric 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.