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 Ta2O 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/SiO2/Si and Pt/Ti/SiO2/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.

Physics and Applications of Bismuth Ferrite

“…[55,56] Bismuth has a low melting temperature of 270 8C, at which it readily forms an eutectic alloy with Bi 2 Pt and, at higher temperatures, other Bi-Pt alloys are also formed. [57] Therefore, it is probably best NOT to use Pt electrodes when probing the high-temperature properties of bismuth-based materials, [58] including bismuth ferrite. We also note that most BiFeO 3 ceramics and single crystals are made in platinum crucibles which, given the high mutual reactivity of Bi and Pt, may not be the most suitable receptacle.…”

Filmes finos de SrBi2Ta2O9 processados em forno microondas

“…Além disso, o chaveamento e a saturação da polarização de filmes SBT podem ser obtidos para tensões abaixo de 3 V. A estrutura cristalina do SBT é ortorrômbica composta por camada de perovskita (SrTa 2 O 7 ) 2-alternadas por camadas de (Bi 2 O 2 ) 2+ [2]. O SBT tem sido preparado por diversas técnicas como decomposição metalorgânica (MOD) [3], deposição de vapor químico de organometálicos (MOCVD) [4], deposição de vapor químico de organometálicos por ressonância (ECR-MOCVD) [5], deposição de solução de organometálicos modificado (MOSD) [6], deposição por laser pulsado (PLD) Filmes finos de SrBi 2 Ta 2 O 9 processados em forno microondas (SrBi 2 Ta 2 O 9 thin films processed in microwave oven) [7], sol-gel [8] e pelo método dos precursores poliméricos [9]. Estas técnicas, aliadas às suas propriedades elétricas, fazem deste material um potencial candidato para fabricação de dispositivos de memórias.…”

Preparation and characterization of SrBi2Nb2O9 thin films made by polymeric precursors

“…1,2 Several deposition techniques have been used to obtain thin films of these compounds, such as pulsed laser ablation, [3][4][5] chemical vapor deposition (CVD), 6,7 metallorganic decomposition (MOD), 8,9 and sol-gel. 10,11 However, these methods require heat treatment at high temperatures, what is seriously deleterious to the Siwafer properties.…”