Preparation of Bi-Based Ferroelectric Thin Films by Sol-Gel Method

Abstract

The effects of Bi/Ta and Sr/Ta mole ratios on ferroelectric properties of Sr x Bi y Ta 2 O z [ SBIT( x / y /2.0); 0.7≤ x ≤1.0, 2.0≤ y ≤2.6] thin-film capacitors were investigated. The SBIT films were grown by the sol-gel method using a spin-on coating on Pt/Ta/SiO 2 /Si and Pt/Ti/SiO 2 /Si substrates. The films were annealed at 800° C for one hour in oxygen atmosphere. Remanent polarization (Pr) depended strongly on the Sr/Ta mole ratio, and increased with decrease of the Sr/Ta mole ratio. On the other hand, Pr was almost independent of the Bi/Ta mole ratio. Scanning electron microscopy (SEM) images show that crystal grains grew with decrease of the Sr/Ta mole ratio. Electron probe micro analyzer (EPMA) analysis revealed that Bi content in SBIT films increased with decrease in Sr composition from stoichiometry.