Defects in alkaline earth titanate thin films - the conduction behavior of doped BST

The conduction behavior of doped BST thin films was determined in dependence of temperature (T) and the ambient oxygen partial pressure (pO(2)) by a special 4-point measurement technique. The studies covered lanthanum as donor and-manganese as acceptor type doping in various concentrations as well as selected compositions of the solid solution series (Ba1-xSrx)TiO3. The external parameters were controlled by use of a YSZ solid state oxygen pump in the temperature range from 700degreesC to 1000degreesC and oxygen atmospheres between 10(-20) and 1 bar. In contrast to the features of bulk materials, our investigations on thin films showed with a sharp drop and a plateau region a quite unusual conduction behavior. Because the classical defect chemical explanation fails, different approaches, which take a more complex defect structure and the dimensions into account, are proposed