ELECTRICAL-TRANSPORT PROPERTIES OF EPITAXIAL BATIO3 THIN-FILMS

Measurements of the temperature dependent transport properties of epit axial BaTiO3 are reported. Electrical resistivity and thermoelectric p ower were measured over the temperature range of 77-300 K. Room temper ature resistivities of the as-deposited, undoped films range from 10(5 ) to 10(8) Omega cm, while values as low as 55 Omega cm are obtained f or the La-doped films. The resistivity shows an activated temperature dependence with the measured activation energies ranging between 0.11 and 0.50 eV. The activation energy depends strongly upon the thin film carrier concentration. Thermoelectric power measurements indicate tha t the films are n-type. The Seebeck coefficient for La-doped BaTiO3 ex hibits metallike behavior, with its magnitude directly proportional to temperature. Temperature dependent resistivity and thermopower measur ements indicate that the carrier mobility is activated. A transport mo del is proposed whereby conduction occurs in the La-doped films via ho pping between localized states within a pseudogap formed between a low er Hubbard band and the BaTiO3 conduction band edge. (C) 1996 American Institute of Physics.