DOPANT INFLUENCE ON DIELECTRIC LOSSES, LEAKAGE BEHAVIOR, AND RESISTANCE DEGRADATION OF SRTIO3 THIN-FILMS

The paper presents an impedance analysis of SrTiO3 thin films with La, Fe, and Mn, respectively, as heterovalent substituents. The films wer e prepared by chemical solution deposition. Dopant concentrations were varied in the range from 0.1 at% to 5 at% for the electrical studies. Aluminum as a low-workfunction metal was employed as the cathode elec trode. The current response upon a d.c. voltage step stimulation was a nalyzed with respect to the relaxation, leakage, and degradation behav iour. The results show that La, as a donor-type substituent, tends to increase the leakage while it reduces the resistance degradation. Low concentrations of Fe and Mn, respectively, decrease the leakage curren t considerably while at higher dopant concentrations the leakage curre nt increases again. The lifetimes are improved by Mn doping and, to a lesser extent, by Fe doping, The dielectric losses and the correspondi ng relaxation currents are only slightly affected by the dopants. The results are discussed in a comparison with literature data on comparab le bulk ceramics and in the light of the defect chemistry of alkaline earth titanates. (C) 1997 Published by Elsevier Science S.A.