Raman Scattering from Perovskite Ferroelectrics

Two-dimensional (2D) ferroelectric films have vast applications due to their dielectric, ferroelectric, and piezoelectric properties that meet the requirements of sensors, nonvolatile ferroelectric random access memory (NVFeRAM) devices, and micro-electromechanical systems (MEMS). However, the small surface area of these 2D ferroelectric films has limited their ability to achieve higher memory storage density in NVFeRAM devices and more sensitive sensors and transducer. Thus, conformally deposited ferroelectric films have been actively studied for these applications in order to create three-dimensional (3D) structures, which lead to a larger surface area. Most of the current methods developed for the conformal deposition of ferroelectric films, such as metal-organic chemical vapor deposition (MOCVD) and plasma-enhanced vapor deposition (PECVD), are limited by high temperatures and unstable and toxic organic precursors. In this paper, an innovative fabrication method for barium titanate (BaTiO3) textured films with 3D architectures is introduced to alleviate these issues. This fabrication method is based on converting conformally grown rutile TiO2 nanowire arrays into BaTiO3 textured films using a simple two-step hydrothermal process which allows for thickness-controlled growth of conformal films on patterned silicon wafers coated with fluorine-doped tin oxide (FTO). Moreover, the processing parameters have been optimized to achieve a high piezoelectric coupling coefficient of 100 pm/V. This high piezoelectric response along with high relative dielectric constant (εr = 1600) of the conformally grown textured BaTiO3 films demonstrates their potential application in sensors, NVFeRAM, and MEMS.

Robust in-plane polarization switching in epitaxial BiFeO3 films

With the significant innovation and rapid development of the nonvolatile ferroelectric random access memory devices (FeRAMs), many efforts have been done to research and develop the ferroelectric films. Bismuth layer-structured ferroelectrics, such as lanthanum-doped bismuth titanate, have been paid a lot of attentions for their super properties. Temperature and ultraviolet irradiation, two of the important factors which can affect the properties of films, have been attracted much attention. In this paper, we mainly investigated the annealing temperature and the ultraviolet irradiation effect on the ferroelectric properties of Bi3.25La0.75Ti3O12 (BLT) thin films.

Annealing effect upon chain orientation, crystalline morphology, and polarizability of ultra-thin P(VDF-TrFE) film for nonvolatile polymer memory device

Development of PZT sputtering method for mass-production

Ferroelectric and piezoelectric oxide nanostructured films for energy harvesting applications

The number of publications and scientific meetings in the field of ferroelectricity has been increasing exponentially in the last 30 years. In addition to the classical fields of phase transitions and critical phenomena four new sub fields have emerged: a) ferroelectric liquid crystals, b) thin films and integrated ferroelectrics which led to the discovery of 2D ferroelectricity and the development of non-volatile ferroelectric random access memory, c) dipolar glasses and relaxors as well as d) incommensurate systems. Quantum effects have been observed as well.

Thin iridium films are required as electrode material for ferroelectric capacitors. SBT (SrBi2Ta2O9) or PZT (Pb(ZrXTi1-X) O3) are often used as ferroelectric material in such capacitors. The PZT based non-volatile ferroelectric random access memories show better fatigue characteristics if platinum is replaced by iridium as electrode material. The iridium films were deposited on different substrates at room temperature by electron gun evaporation and at temperatures of 300 - 500 {degree sign}C by liquid-delivery MOCVD. The precursor Ir(EtCp) (1,5COD) [iridium(ethylcyclopentadienyl)(1,5-cyclooctadiene)] was diluted in toluene (0.1 M concentration) for the deposition experiments. The iridium films were deposited onto TiO2/SiO2/Si-, SiO2/Si-, and Si-substrates to compare the iridium film properties on different substrates. Annealing in an oxidizing ambient at temperatures above 700 {degree sign}C resulted in an increased oxidation of the CVD - films as proved by XRD analyses. Low resistivities of 7 - 70 µWcm were obtained for the as-deposited iridium films.

From the Publisher: Thin Film Ferroelectric Materials and Devices is a compilation of current research and development in two very important ferroelectric device technologies, namely ferroelectrics for Dynamic Random Access Memories (DRAM's) and Non-Volatile Ferroelectric Random Access Memories (NV-FRAM's). Given the rapid pace of development and the broad scope of the general topic of ferroelectric materials, readers will benefit from such a focused presentation. Thin Film Ferroelectric Materials and Devices will be of great value to materials and device scientists, device and process engineers, students, and postdoctoral associates. Furthermore, this compilation will serve as a concise introduction for new entrants to this exciting field.

Rapid screening B-site doping ferroelectric perovskite with high curie temperature for electronic applications by a novel IDBO-RF approach

Since ferroelectric capacitors prepared by 1-mask etching are degraded after the etching, we systematically investigated the origin of the degradation. It was found that the major degradation originates from the formation of the nonstoichiometric and amorphorized Pb(ZrxTi1-x)O3 (PZT) layer on the sidewall of the PZT film during etching of the bottom electrode (BE). Therefore, to eliminate the undesired etch-damaged layer, we developed a novel etching technology using a ferroelectric (FE) sidewall spacer, which results in the enhancement of the remnant polarization after completing the capacitor etching process. Using the novel FE sidewall spacer, the sensing margin of bit-line-developed voltage was improved to 400 mV, which can guarantee highy reliable high-density ferroelectric random access memory (FRAM) devices.

Abstract

Ferroelectric thin film capacitors are promising candidates for non-volatile ferroelectric Random Access Memories (FeRAM's) as they exhibit a switchable polarization. There are three important failure-mechanisms influencing the performance of these capacitors and disturbing the long-term stability and reliability under operation conditions fatigue, retention, and imprint. The imprint effect of lead zirconate titanate (PZT) thin films was investigated in this paper. Establishing and maintaining a polarization state leads to a shift of the hysteresis loop on the voltage axis and also to a loss of polarization. The voltage shift as well as the loss of polarization can cause a failure of the ferroelectric memory cell (read and write failure). The experimental results obtained on PZT films are discussed in view of the predictions of imprint models proposed in the literature.

The integration of thin film ferroelectrics with silicon processing is being implemented for various types of devices. The technology is based on the sputtering or chemical deposition of lead-based perovskites such as lead zirconate titanate. Factors concerned with the integration of ferroelectric films with semiconductor processing are described. Major interests in Canada include nonvolatile ferroelectric random access memories for high-speed digital or long-term analog memory applications, high-density capacitors, electro-optic switches, and a wide range of sensors and actuators integrated into silicon.

The fabrication of ferroelectric nanocrystal materials such as Pb(Zr,Ti)O3 has been widely researched because of the development of high capacity ferroelectric random access memory devices (FeRAM) and ferroelectric domain physics at the nano scale. The ultra flat surface of electrically conductive materials such as Pt is required for the deposition of the ferroelectric nanocrystal substrate. In this paper, Pt deposition was performed using our newly developed sputtering method (low angle incidence sputtering) on an atomically flat sapphire substrate. Due to Volmer-Waber growth, the sputtered Pt grew into island crystals at the normal deposition rate. However, lateral growth of Pt occurred at a very low rate, and the ultra thin atomically flat Pt layer could be obtained on the atomically flat sapphire surface. The Pt thin layer was also evaluated using electrically conductive atomic force microscope (C-AFM) measurement, confirming electric conduction of the atomically flat Pt layer. The obtained atomically flat Pt layer is expected to be utilized for electrical evaluation of PbTiO 3 nanocrystal array.