THICKNESS DEPENDENCE OF ROOM-TEMPERATURE PERMITTIVITY OF POLYCRYSTALLINE BATIO3 THIN-FILMS BY RADIOFREQUENCY MAGNETRON SPUTTERING

Polycrystalline BaTiO3 thin films with thickness ranging from 2100 to 20 000 Angstrom were prepared on platinum substrates using off-axis ra dio-frequency magnetron sputtering. The variation in room temperature permittivity of the films was investigated with respect to thickness u sing x-ray diffraction and transmission electron microscopy, All films were ferroelectric and their room temperature permittivity, which was significantly higher than previously reported values, showed a strong dependence on film thickness. Higher permittivity was attributed prim arily to the presence of ferroelectric domains. The room temperature p ermittivity of the thin films showed large variations with grain size, as in the case of BaTiO3 ceramics, The increase in permittivity with increasing film thickness was attributed to the decrease in defect con centration with grain growth, The 20 000 Angstrom film showed an abrup t decrease in permittivity and the presence of an intergranular phase having titanium-excess composition; these phenomena are discussed in t erms of domain boundary pinning and recrystallization. (C) 1997 Americ an Institute of Physics.