CRYSTAL-STRUCTURE, MICROSTRUCTURE, AND ELECTRICAL-PROPERTIES IN NONSTOICHIOMETRIC SBT THIN-FILMS

The relation between the electrical properties and the microstructure of the layered-perovskite SET thin films were studied. The crystal str ucture of the powder SET samples were also analyzed by the Rietveld re finement method for clarifying the relationship between the two. The R ietveld refinement results for the Sr1Bi2Ta2O9, Sr0.7Bi2Ta2O9, Sr0.7Bi 2.2Ta2O9, and (Sr0.87Bi0.13)Bi-2(Ta1.93Bi0.07)O-9 samples showed that excess-Bi occupies the Sr site forming (Sr1-3/2xBix)Bi2Ta2O9 solid sol ution. The Sr0.7Bi2Ta2O9 and (Sr0.87Bi0.13)Bi-2(Ta1.93Bi0.07)O-9 sampl es produced minor impurity phases in addition the major SET phase. The SET thin films with molar ratio (Sr:Bi:Ta) of 1:2:2, 0.7:2.2:2, 1.87: 2.2:1.93, 1:2.2:2 and 0.7:2:2 were prepared by MOD method. The spin-co ated films were crystallized at 750 degrees C for 1 hour under O-2 Rem anent polarization of the thin films critically depended on the crysta llinity and grain size, while the leakage current density depended on the minor impurity phase contained in the thin films. The 0.7:2.2:2 th in films showed the best electrical properties: 2P(r) = 8.2 mu C/cm(2) , E-c = 43.6KV/cm, J(leakage current) = 6.4x10(-8) A/cm(2) at 3V.