Electrical properties and crystal structures of (Ba,Sr)TiO3 films and BaRuO3 bottom electrodes prepared by sputtering

Abstract

(Ba,Sr)TiO3 (BST) films were synthesized on BaRuO3 (BRO) using radio-frequency magnetron sputter deposition. Conductive (similar to 1 m Omega cm) BRO layers of (110) texture were produced at a deposition temperature T-d = 400 degrees C, about 200 degrees C lower than that of SrRuO3. The BST (100 nm) deposited on the BRO showed a (110) preferred orientation and crystallization formation at temperatures as low as 200 degrees C. An interfacial layer and the local epitaxial growth of BST on BRO layers within columnar grains were confirmed by high-resolution transmission-electron microscopy studies. Uniform I-V characteristics (I < 1 x 10(-7) A/cm(2)) for bias voltages in the range 0.0-3.0 V of all the BST films deposited within T-d = 300-500 degrees C were observed. The dielectric constants of the BST films (e.g., epsilon(r) = 300 at T-d = 400 degrees C) are considerably higher than those generally achievable for the same T-d by using Pt bottom electrodes. The dependence of the annealing atmosphere (N-2 and O-2) Of the dielectric constants was studied and attributed to a diffused BST/BRO interfacial layer which is semiconductive in a reduced state and insulating in an oxidized state. (C) 1998 American Institute of Physics. [S0003-6951(98)01910-X].