Study of Electrical and Photoferroelectric Properties of Lead Zirconate Titanate Thin Films Prepared by Pulsed Laser Deposition for Ferroelectric Memories

Study of Electrical and Photoferroelectric Properties of Lead Zirconate Titanate Thin Films Prepared by Pulsed Laser Deposition for Ferroelectric Memories PDF Author: Jaichan Lee
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ISBN:
Category :
Languages : en
Pages : 396

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Scientific and Technical Aerospace Reports

Scientific and Technical Aerospace Reports PDF Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 694

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Development of Lead-free Piezoelectric Thin Films by Pulsed Laser Deposition

Development of Lead-free Piezoelectric Thin Films by Pulsed Laser Deposition PDF Author: Maryam Abazari Torghabeh
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ISBN:
Category : Ferroelectric devices
Languages : en
Pages : 193

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As a high performance piezoelectric material widely used in sensors, actuators and other electronic devices, lead zirconate titanate (PZT) ceramics have been the center of attention for many years. However, the toxicity of these materials and their exposure to the environment during processing steps, such as calcination, sintering, machining as well as problems in recycling and disposal have been major concerns regarding their usage all around the globe for the past couple of decades. Consequently, utilizing lead-based materials for many commercial applications have been recently restricted in Europe and Asia and measures are being taken in United States as well. Therefore, there is an urgent need for lead-free piezoelectrics whose properties are comparable to those of well-known PZT materials. Recently, the discovery of ultra-high piezoelectric activity in the ternary lead-free KNaNbO3-LiTaO3-LiSbO3 (KNN-LT-LS) and (Bi, Na)TiO3-(Bi, K)TiO3-BaTiO3 (BNT-BKT-BT) systems have given hope for alternatives to PZT. Furthermore, the demand for new generation of environment-friendly functional devices, utilizing piezoelectric materials, inspired a new surge in lead-free piezoelectric thin film research. In this study, an attempt has been made to explore the development of lead-free piezoelectric thin films by Pulsed Laser Deposition (PLD) on SrTiO3 substrate. While the growth and development process of KNN-LT-LS thin films was the primary goal of this thesis, a preliminary effort was also made to fabricate and characterize BNT-BKT-BT thin films. In a comprehensive and systematic process optimization study in conjunction with X-ray diffractometry, the phase evolution, stoichiometry, and growth orientation of the films are monitored as a function of deposition conditions including temperature and ambient oxygen partial pressure. Processing parameters such as substrate temperature and pressure are shown to be highly dominant in determining the phase and composition of the films. Oxygen partial pressure has shown to control the chemical composition of the films through solid-gaseous phase equilibrium and substrate temperature has mostly influenced the growth mode and microstructure. Findings of this study has shown that 300-500 nm single-phase epitaxial KNN-LT-LS and BNT-BKT-BT thin films could indeed be obtained at a temperature of 700-750 oC and 300-400 mTorr of oxygen partial pressure. Following a series of studies on effect of doping, it was revealed that addition of 1 mol% Mn to KNN-LT-LS composition resulted in a significant suppression of leakage current and enhancement of polarization saturation. A remanent polarization of 16 æC/cm2 and coercive field of 20 kV/cm were measured for such thin film, which are comparable to those of hard PZT counterparts. Also, a high remanent polarization and coercive field of 30 æC/cm2 and 95 kV/cm were achieved in 350 nm BNT-BKT-BT thin films. Longitudinal (d33) and transverse (e31, f) piezoelectric coefficients of KNN-LT-LS thin films were found to be 55 pm/V and -4.5 C/m2 respectively, prepared at the optimized conditions, whereas 350 nm BNT-BKT-BT thin films exhibited an e31, f of -2.25 C/m2. The results of this study present the great potential of KNN-LT-LS and BNT-BKT-BT thin films for piezoelectric MEMS devices and provide a baseline for future investigations on lead-free piezoelectric thin films.

American Doctoral Dissertations

American Doctoral Dissertations PDF Author:
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Category : Dissertation abstracts
Languages : en
Pages : 704

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Preparation, Microstructure, and Ferroelectric Properties of Laser-Deposited Thin Batio Sub3 and Lead Zirconate-Titanate Films

Preparation, Microstructure, and Ferroelectric Properties of Laser-Deposited Thin Batio Sub3 and Lead Zirconate-Titanate Films PDF Author: P. S. Brody
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ISBN:
Category :
Languages : en
Pages : 13

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Ferroelectric thin films of BaTiO3 and lead zirconate titanate, PbZro. 53Tio. 4703 (PZT), have been prepared by pulsed excimer laser deposition. The microstructure and crystallography of these films have been studied by scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDX), transmission electron microscopy (TEM), xray diffraction (XRD), and differential scanning calorimetry (DSC). Electrical properties, including remanent polarization, dielectric loss, and dielectric constant, have been measured. Also, switched remanent polarization has been measured under conditions of continuous cycling.

Ferroelectric Thin Films

Ferroelectric Thin Films PDF Author:
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Category : Ferroelectric thin films
Languages : en
Pages : 564

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Pulsed Laser Deposition of Lead Zirconate Titanate Thin Films

Pulsed Laser Deposition of Lead Zirconate Titanate Thin Films PDF Author: Lucymarie Mantese
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Category :
Languages : en
Pages : 146

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Ferroelectric Thin Films II

Ferroelectric Thin Films II PDF Author: Angus I. Kingon
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ISBN: 9781558991378
Category : Technology & Engineering
Languages : en
Pages : 616

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Piezoelectric and Ferroelectric Properties of Lead Zirconate Titanate Thin Films

Piezoelectric and Ferroelectric Properties of Lead Zirconate Titanate Thin Films PDF Author: Dong-Joo Kim
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ISBN:
Category : Microelectromechanical systems
Languages : en
Pages : 434

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Bismuth Magnesium Titante - Lead Titanate Thin FIlms for High Temperature Ferroelectric Memory

Bismuth Magnesium Titante - Lead Titanate Thin FIlms for High Temperature Ferroelectric Memory PDF Author: Carl Sebastian Morandi
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Category :
Languages : en
Pages :

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This work provides a comprehensive study on the development of 35Bi(Mg1/2Ti1/2)O3-65PbTiO3 thin films deposited by pulsed laser deposition, detailing the effects of processing variables on the film composition and resulting electrical properties. The primary application focus is on a potential high temperature ferroelectric layer for ferroelectric random access memory (FeRAM) devices. To assess whether 35BiMT-65PT thin films are of interest for this application, the films were assessed by determining the switchable polarization, the dielectric properties and their thickness dependence, the high temperature polarization and dielectric properties, and the retention characteristics.For pulsed-laser deposited 35BiMT-65PT films on 36 nm thick PbTiO3 or 16 nm thick 5 mol% La-doped PbTiO3 seed layers, the processing window for developing a perovskite structure was found to be wide. Within the detection limits of x-ray diffraction, scanning electron microscopy and transmission electron microscopy, the films were found to be phase pure perovskite for growth temperatures from 600 C to 700 C at O2(90%)/O3(10%) background pressures of 100-300 mTorr. Target compositions from 10 mol% to 85 mol% excess Pb produced phase pure perovskite films when depositing at 700 C and a 10 Hz laser repetition rate. The film composition was found to vary as a function of processing parameters. As the chamber pressure during deposition decreased, the film Mg and Pb concentration decreased, while the concentration of Bi increases. For films on 36 nm PbTiO3 seed layers, the remanent polarization, Pr, increased 64% to 21 C/cm2 and the polarization electric field loops rotated counterclockwise as the deposition pressure increased from 60 mTorr to 340 mTorr. Decreasing the seed layer thickness from 36 to 16 nm led to a decrease in Pr to 14 C/cm2. Adjusting the target composition allowed the deposition of films which had near-stoichiometric Bi and Mg concentrations, but in all cases, the grown films were lead deficient. These films had remanent polarizations of 18 to 20 C/cm2. If the lead content of the target was increased too far, the remanent polarization decreased, possibly due to the need to evolve more PbO from defective growth layers. Finally, the deposition rate showed no substantial effect on the film composition, but did have a significant impact on the ferroelectric properties. As the deposition rate decreased, the Pr increased to 22 C/cm2 presumably due to enhanced crystalline quality and time for atomic rearrangement. At laser frequencies of 5 Hz, a Mg-rich pyrochlore phase begins to form and films showed a maximum Pr 22 C/cm2. The optimal processing window for the maximum in ferroelectric properties shifts to higher PbO excess contents in the target as the deposition rate decreased. A film deposited at 5 Hz with a 65 mol% Pb, 20 mol% Bi, and 10 mol% Mg excess target had the maximum Pr 25 C/cm2. The processing-composition behavior is explained via preferential adsorption of Bi on the A-site, which results in lead vacancies.The dielectric, polarization and leakage properties of 35BiMT-65PT thin films with varying levels of A-site deficiency were investigated as a function of thickness and/or temperature. PbTiO3 seed layers utilized to nucleate the perovskite phase in A-site deficient films induced a thickness dependence to the ferroelectric hysteresis and dielectric permittivity. Adjusting for this, the dielectric response of the 35BiMT-65PT films is 960. The dielectric permittivity maximum was 430 C at 1 MHz for A-site deficient films. The transition temperature is independent of film thickness to 85 nm. Tan() remains less than 15% at 1 MHz, regardless of film thickness and temperature up to 585 C. High temperature polarization-electric field hysteresis measurements show charge injection with is exacerbated on increasing temperature, while PUND measurements show little temperature dependence of Pr up to temperatures of 200 C. Poole-Frenkel emission dominated the high field leakage behavior. The refractive index measured by ellipsometry is 2.58 at 633 nm. All samples show significant retention loss. As the stoichiometry improves, retention improves such that >40% of the initial P is retained over 280 min. at room temperature. To remove the influence of the PbTiO3 seed layers on the apparent thickness dependence of 35BiMT-65PT, films without a PbTiO3 seed layer were deposited. Similar to their seed layer counterparts, seedless films show phase purity within the same target composition range investigated for films on seed layers. Phase pure films show somewhat reduced thickness dependent dielectric properties with respect to seeded films. Pr measured at 10 kHz for seedless films was 22-25 C/cm2 until thicknesses of 200 nm and decreased to 15.5 C/cm2 for films that were 100 nm thick. I-V measurements of seedless films deposited under nominally the same conditions as seeded films resulted in higher leakage compared to seeded films. Deposition under an Ar/O2 atmosphere decreased the leakage behavior by up to five times. Films grown under the optimum 50%O2/50%Ar atmosphere demonstrate little temperature dependence in Pr up to 200 C. As temperature increases, the DC dielectric breakdown of strength of seedless films decreases faster compared to seeded films. Retention analysis shows similar behavior to that of seeded films.