Effect of bottom electrodes on dielectric relaxation and defect analysis of (Ba0.47Sr0.53)TiO3 thin film capacitors

The dielectric relaxation and defect analysis of (Ba0.47Sr0.53)TiO3 (BST) thin films deposited on various bottom electrodes, such as Pt, Ir, IrO2/Ir, Ru, RuO2/Ru before and after annealing in O-2 ambient was investigated. Through the measurement of dielectric dispersion as a function of frequency (100 Hz less than or equal to f less than or equal to 10 MHz) and temperature (27 degrees C less than or equal to T less than or equal to 150 degrees C), we studied the trapping dielectric relaxation and defect quantity of the films, and proposed an equivalent circuit on the basis of the capacitance, admittance and impedance spectra. A shallow trap level located at 0.005-0.01 eV below the conduction band was observed from the admittance spectral studies in the temperature range of 27-150 degrees C. The origin of dielectric relaxation and defect concentration was attributed to the existence of the grain boundary defect, interface defect and shallow trap level in the films. An equivalent circuit was established which can well explain the AC response and identify the contribution of defects on electrical properties of BST thin film. From the viewpoint of trapping phenomena and dielectric relaxation analyses, we propose Ir as the optimum material for bottom electrode to withstand the post-annealing treatment. (C) 1998 Elsevier Science S.A. All rights reserved.