Effects of growth temperature and film thickness on the electrical properties of Ba0.7Sr0.3TiO3 thin films grown on platinized silicon substrates by pulsed laser deposition

Barium strontium titanate Ba0.7Sr0.3TiO3 (BST) thin films, with different growth temperatures (T.) as well as different film thicknesses, have been prepared on Pt/Ti/SiO2/Si substrates by a reactive pulsed laser deposition method. We observed strong dependences of dielectric properties, such as the Curie-Weiss temperature, dielecttic constant, loss tangent, dielectric tunability and leakage current, on the T-g, and the BST film thickness. With increase of T, from 630 to 750 degrees C, the dielectric constant gradually increases due to the increase in the crystallinity and the grain size. However, the dielectric tunability, loss tangent and leakage current characteristics drastically degrade when the T, increases up to 750 degrees C, due to the diffuse and rough interface. The BST film grown at 690 degrees C shows the best overall dielectric properties with a figure-of-merit of 33 (at 400 kV/cm). These results suggest that film growth process could be optimized by systematically investigating the structure-property relationships. Furthermore, as the BST film thickness increases from 250 to 560 nm, the dielectric properties are remarkably enhanced. The film thickness effect is attributed to the interfacial low-dielectric layers (the so-called "dead layer") between the BST film and both metal electrodes, which is well explained in terms of a series capacitor model. The thickness and the average dielectric constant for the dead layer are experimentally estimated to be 1.9 nm and 20.3, respectively, in Pt/BST/Pt capacitors. (c) 2005 Elsevier B.V. All rights reserved.