Photoluminescence in Low-Dimensional Oxide Ferroelectric Materials

Abstract

Ferroelectric materials exhibit important multifunctional electrical properties such as ferroelectric, dielectric, piezoelectric, pyroelectric, and electrooptic properties. They can be used to fabricate various microelectronic and optoelectric devices including nonvolatile ferroelectric random access memories, microsensors and microactuators, integrated capacitors, and electrooptic modulators [1-3]. Widely studied ferroelectric materials include Pb(Zr,Ti)O3 (PZT), lanthanide doped Bi4Ti3O12 (BiT), and BaTiO3. PZT is the most important piezoelectric material which has been used in various electronic devices. BaTiO3 and its solid solution with SrTiO3 exhibit high dielectric constant and other advantageous properties. Lanthanide doped BiT gained great interest on searching new ferroelectric thin films with fatigue-free polarization properties for non-volatile random access memories. Among them, La doped bismuth titanate and Nd-doped bismuth titanate exhibit excellent electrical properties such as high fatigue resistance, good retention, fast switching speed, high Curie temperature, large spontaneous polarization, and small coercive field [2-4]. In addition, lanthanide doped BiT do not contain lead, thus, environmental pollution and harm to health of human due to lead volatility in PZT can be avoided. Studies in the past decade indicate that lanthanide doped bismuth titanate ferroelectric thin films are the most promising candidate materials for nonvolatile ferroelectric random access memory applications. Most efforts have been devoted to improving the electrical properties of Bi4Ti3O12 (BIT) thin films by rare earth ion doping for the development of non-volatile ferroelectric random access memory applications [5-7]. It is worth pointing out that besides excellent ferroelectric polarization fatigue-free characteristics, the bismuth layered perovskite structure ferroelectric thin films also exhibit good piezoelectric properties and large optical nonlinearity [8-10]. Recently, photoluminescence (PL) properties originated from defects or rare earth ions in oxide ferroelectric materials have attracted much attention for possible integrated photoluminescent ferroelectric device applications. This paper briefly reviews the status and new progress on study of photoluminescence in low-dimensional oxide ferroelectric materials including ferroelectric thin films, nanopowders, nanorods or nanowires, and nanotubes, and some of our own research work in this field with an emphasis on the photoluminescence properties of lanthanide doped bismuth titanate thin films such as (Bi,Pr)4Ti3O12, (Bi,Eu)4Ti3O12, (Bi,Er)4Ti3O12, and codoped bismuth titanate thin films will be presented in this paper, also.