Download or read book An Investigation Into Controlling the Growth Modes of Ferroelectric Thin Films Using Pulsed Laser Deposition and RHEED written by Sean Robert Craig McMitchell and published by . This book was released on 2008 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Investigation Into Controlling the Growth Modes of Ferroelectric Thin Films Using Pulsed Laser Deposition and RHEED written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin film ferroelectricss are widely considered for tunable microwave applications, the reduced small dimensions leading to low tuning voltages. The incipient ferroelectric strontium titanate is an ideal solution for tunable microwave devices, particularly in conjunction with high temperature superconductors. It has no spontaneous polarisation yet possesses a large permittivity at low temperatures that is sensitive to an electric field bias with relatively low loss. For such applications it is essential to use a low loss substrate such as magnesium oxide. In general, thin films have less favourable dielectric properties compared with their bulk counterparts due to differences in microstructure. strontium titanate films on MgO substrate prove difficult to grow due to the high lattice mismatch and issues connected with chemical incompatibility at the film/substrate interface. It has been shown here that it is possible to engineer the growth mode of this system, altering the strain and the defect concentration. These are both known factors influencing the dielectric properties of thin films. Reflection high energy electron diffraction (RHEED) in combination with interval pulsed laser deposition (PLD) has been used to achieve a two dimensional, layer-by-layer growth mode. Crucial to this was the deposition of a unit-cell thick titanium dioxide buffer layer on the surface, the deposition of which was also controlled by RHEED. The growth mode and microstructure of films grown using standard PLD with and without the buffer layer and films grown by interval PLD with and without the buffer layer have been compared by analysis of the RHEED data and transmission electron microscopy. This is the first time layer-by-layer growth has been achieved in this highly-mismatched epitaxial systems. The results point the way towards control of defects in oxide thin films from which microstructure-property relationships may be more clearly determined.
Download or read book Current Research in Pulsed Laser Deposition written by Liviu Duta and published by MDPI. This book was released on 2021-08-30 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: Despite its limitation in terms of surface covered area, the PLD technique still gathers interest among researchers by offering endless possibilities for tuning thin film composition and enhancing their properties of interest due to: (i) the easiness of a stoichiometric transfer even for very complex target materials, (ii) high adherence of the deposited structures to the substrate, (iii) controlled degree of phase, crystallinity, and thickness of deposited coatings, (iv) versatility of the experimental set-up which allows for simultaneous ablation of multiple targets resulting in combinatorial maps or consecutive ablation of multiple targets producing multi-layered structures, and (v) adjustment of the number of laser pulses, resulting in either a spread of nanoparticles, islands of materials or a complete covering of a surface. Moreover, a variation of PLD, known as Matrix Assisted Pulsed Laser Evaporation, allows for deposition of organic materials, ranging from polymers to proteins and even living cells, otherwise difficult to transfer unaltered in the form of thin films by other techniques. Furthermore, the use of laser light as transfer agent ensures purity of films and pulse-to-pulse deposition allows for an unprecedented control of film thickness at the nm level. This Special Issue is a collection of state-of-the art research papers and reviews in which the topics of interest are devoted to thin film synthesis by PLD and MAPLE, for numerous research and industry field applications, such as bio-active coatings for medical implants and hard, protective coatings for cutting and drilling tools withstanding high friction and elevated temperatures, sensors, solar cells, lithography, magnetic devices, energy-storage and conversion devices, controlled drug delivery and in situ microstructuring for boosting of surface properties.
Download or read book Handbook of Laser Micro and Nano Engineering written by KOJI SUGIOKA. and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook provides a comprehensive review of the entire field of laser micro and nano processing, including not only a detailed introduction to individual laser processing techniques but also the fundamentals of laser-matter interaction and lasers, optics, equipment, diagnostics, as well as monitoring and measurement techniques for laser processing. Consisting of 11 sections, each composed of 4 to 6 chapters written by leading experts in the relevant field. Each main part of the handbook is supervised by its own part editor(s) so that high-quality content as well as completeness are assured. The book provides essential scientific and technical information to researchers and engineers already working in the field as well as students and young scientists planning to work in the area in the future. Lasers found application in materials processing practically since their invention in 1960, and are currently used widely in manufacturing. The main driving force behind this fact is that the lasers can provide unique solutions in material processing with high quality, high efficiency, high flexibility, high resolution, versatility and low environmental load. Macro-processing based on thermal process using infrared lasers such as CO2 lasers has been the mainstream in the early stages, while research and development of micro- and nano-processing are becoming increasingly more active as short wavelength and/or short pulse width lasers have been developed. In particular, recent advances in ultrafast lasers have opened up a new avenue to laser material processing due to the capabilities of ultrahigh precision micro- and nanofabrication of diverse materials. This handbook is the first book covering the basics, the state-of-the-art and important applications of the dynamic and rapidly expanding discipline of laser micro- and nanoengineering. This comprehensive source makes readers familiar with a broad spectrum of approaches to solve all relevant problems in science and technology. This handbook is the ultimate desk reference for all people working in the field.
Download or read book Fundamental Mechanisms of Roughening and Smoothing During Thin Film Deposition written by and published by . This book was released on 2016 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this research program, we have explored the fundamental limits for thin film deposition in both crystalline and amorphous (i.e. non-crystalline) materials systems. For vacuum-based physical deposition processes such as sputter deposition, the background gas pressure of the inert gas (usually argon) used as the process gas has been found to be a key variable. Both a roughness transition and stress transition as a function of pressure have been linked to a common mechanism involving collisions of energetic particles from the deposition source with the process inert gas. As energetic particles collide with gas molecules in the deposition process they lose their energy rapidly if the pressure (and background gas density) is above a critical value. Both roughness and stress limit important properties of thin films for applications. In the area of epitaxial growth we have also discovered a related effect; there is a critical pressure below which highly crystalline layers grow in a layer-by-layer mode. This effect is also though to be due to energetic particle thermalization and scattering. Several other important effects such as the observation of coalescence dominated growth has been observed. This mode can be likened to the behavior of two-dimensional water droplets on the hood of a car during a rain storm; as the droplets grow and touch each other they tend to coalesce rapidly into new larger circular puddles, and this process proceeds exponentially as larger puddles overtake smaller ones and also merge with other large puddles. This discovery will enable more accurate simulations and modeling of epitaxial growth processes. We have also observed that epitaxial films undergo a roughening transition as a function of thickness, which is attributed to strain induced by the crystalline lattice mismatch with the substrate crystal. In addition, we have studied another physical deposition process called pulsed laser deposition. It differs from sputter deposition due to the pulsed nature of the deposition where particles arrive at the growth surface in an interval of a few microseconds. We have observed effects such as transient formation of two dimensional islands on elemental crystalline surfaces. Pulsed deposition may also lead to non-equilibrium phases in some cases, such as the observation anomalously high tetragonality for ferroelectric thin films. All of the results described above feature in-situ synchrotron X-ray scattering as the main experimental method, which has become an indispensable technique for observing the kinetics of structures forming in real-time. We have also investigated in-situ coherent X-ray scattering and have developed methods to characterize temporal correlations that are not possible to observe with low-coherence X-rays. A high profile result of this work is a new technique to monitor defect propagation velocities in thin films. This has practical significance since defects limit the properties of thin films and it is desirable to understand their properties and origin in order to control them for practical applications. More broadly, amorphous thin films and multilayers have applications in optical devices, including mirrors and filters. Epitaxial thin films and multilayers have applications in electronic devices such as ferroelectric multilayers for non-volatile data storage, and thermoelectric nanostructures for energy conversion. Our progress in this project points the way for improved deposition methods and for improved simulation and modeling of thin film deposition processes for nanoscale control of materials with novel applications in these areas.
Download or read book Integration of Multi functional Oxide Thin Film Heterostructures with III V Semiconductors written by Md Shafiqur Rahman and published by . This book was released on 2017 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Integration of multi-functional oxide thin films with semiconductors has attracted considerable attention in recent years due to their potential applications in sensing and logic functionalities that can be incorporated in future system-on-a-chip devices. III-V semiconductor, for example, GaAs, have higher saturated electron velocity and mobility allowing transistors based on GaAs to operate at a much higher frequency with less noise compared to Si. In addition, because of its direct bandgap a number of efficient optical devices are possible and by oxide integrating with other III-V semiconductors the wavelengths can be made tunable through hetero-engineering of the bandgap. This study, based on the use of SrTiO3 (STO) films grown on GaAs (001) substrates by molecular beam epitaxy (MBE) as an intermediate buffer layer for the hetero-epitaxial growth of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and room temperature multiferroic BiFeO3 (BFO) thin films and superlattice structures using pulsed laser deposition (PLD). The properties of the multilayer thin films in terms of growth modes, lattice spacing/strain, interface structures and texture were characterized by the in-situ reflection high energy electron diffraction (RHEED). The crystalline quality and chemical composition of the complex oxide heterostructures were investigated by a combination of X-ray diffraction (XRD) and X-ray photoelectron absorption spectroscopy (XPS). Surface morphology, piezo-response with domain structure, and ferroelectric switching observations were carried out on the thin film samples using a scanning probe microscope operated as a piezoresponse force microscopy (PFM) in the contact mode. The magnetization measurements with field cooling exhibit a surprising increment in magnetic moment with enhanced magnetic hysteresis squareness. This is the effect of exchange interaction between the antiferromagnetic BFO and the ferromagnetic LSMO at the interface. The integration of BFO materials with LSMO on GaAs substrate also facilitated the demonstration of resistive random access memory (ReRAM) devices which can be faster with lower energy consumption compared to present commercial technologies. Ferroelectric switching observations using piezoresponse force microscopy show polarization switching demonstrating its potential for read-write operation in NVM devices. The ferroelectric and electrical characterization exhibit strong resistive switching with low SET/RESET voltages. Furthermore, a prototypical epitaxial field effect transistor based on multiferroic BFO as the gate dielectric and ferromagnetic LSMO as the conducting channel was also demonstrated. The device exhibits a modulation in channel conductance with high ON/OFF ratio. The measured nanostructure and physical-compositional results from the multilayer are correlated with their corresponding dielectric, piezoelectric, and ferroelectric properties. These results provide an understanding of the heteroepitaxial growth of ferroelectric (FE)-antiferromagnetic (AFM) BFO on ferromagnetic LSMO as a simple thin film or superlattice structure, integrated on STO buffered GaAs (001) with full control over the interface structure at the atomic-scale. This work also represents the first step toward the realization of magnetoelectronic devices integrated with GaAs (001).
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1556 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ferroelectric Thin Films written by and published by . This book was released on 2005 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thin Film Growth Techniques for Low Dimensional Structures written by R.F.C. Farrow and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work represents the account of a NATO Advanced Research Workshop on "Thin Film Growth Techniques for Low Dimensional Structures", held at the University of Sussex, Brighton, England from 15-19 Sept. 1986. The objective of the workshop was to review the problems of the growth and characterisation of thin semiconductor and metal layers. Recent advances in deposition techniques have made it possible to design new material which is based on ultra-thin layers and this is now posing challenges for scientists, technologists and engineers in the assessment and utilisation of such new material. Molecular beam epitaxy (MBE) has become well established as a method for growing thin single crystal layers of semiconductors. Until recently, MBE was confined to the growth of III-V compounds and alloys, but now it is being used for group IV semiconductors and II-VI compounds. Examples of such work are given in this volume. MBE has one major advantage over other crystal growth techniques in that the structure of the growing layer can be continuously monitored using reflection high energy electron diffraction (RHEED). This technique has offered a rare bonus in that the time dependent intensity variations of RHEED can be used to determine growth rates and alloy composition rather precisely. Indeed, a great deal of new information about the kinetics of crystal growth from the vapour phase is beginning to emerge.
Download or read book Pulsed Laser Deposition of Ferroelectric Thin Films in Conjunction with Superconducting Oxides written by and published by . This book was released on 1994 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The possibility of combining ferroelectrics and superconductors has been of interest for use in memory storage devices. Additionally, superconductors offer crystal structures compatible to the epitaxial growth of the ferroelectric, Ba(0.6)Sr(0.4)TiO3 (BSTO), which is cubic at this stoichiometry. BSTO has a lattice constant of 3.94 A as compared to the superconducting Pr(2-x)Ce(x)CuO4 tetragonal single crystal which also has a lattice constant of a=3.94 A. (minor variations with Cerium content). In this study, ferroelectric thin films of BSTO were deposited on single crystals of Pr2CuO4 and Pr(2-x)Ce(x)CuO4. The optical constants of the substrates, single crystals of Pr2CuO4 and Pr(2-x)Ce(x)CuO4, were determined using Variable Angle Spectroscopic Ellipsometry (VASE) and the composition and crystal structure were examined using Rutherford Backscattering Spectrometry (RBS) with ion beam channeling. The substrate/film interfaces and the compositional variation in the films were also studied with RBS and with SEM/EDS. Glancing angle x-ray diffraction was used to verify the epitaxial nature of the films. The effect of the deposition parameters (laser repetition rate, oxygen backfill pressure, and deposition geometry) on the quality of the films was experimented with previously and only the optimized parameters were used. (jg).
Download or read book Ferroelectric Thin Films XII Volume 784 written by and published by . This book was released on 2004-04-09 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt: The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners. This book, first published in 2004, offers scientific and technological information on ferroelectric thin films from an international mix of academia, industry and government organizations.
Download or read book Advances in Research and Development written by and published by Academic Press. This book was released on 1997-11-14 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: Significant progress has occurred during the last few years in device technologies and these are surveyed in this new volume. Included are Si/(Si-Ge) heterojunctions for high-speed integrated circuits, Schottky-barrier arrays in Si and Si-Ge alloys for infrared imaging, III-V quantum-well detector structures operated in the heterodyne mode for high-data-rate communications, and III-V heterostructures and quantum-wells for infrared emissions.
Download or read book Fabrication of Thin Films by Pulsed Laser Deposition for Clean Energy Applications written by Xiaojun Zhang and published by . This book was released on 2011 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pulsed laser deposition (PLD) is a physical vapor deposition technique for thin film fabrication. Compared with other techniques, pulsed laser deposition technique has advantages such as stoichiometry, flexibility, versatility, lower deposition temperature, ability to grow metastable materials. Because of these advantages, pulsed laser deposition has been widely used in materials research. In this dissertation, pulsed laser deposition has been used to grow thin films for solid oxide fuel cell, light-emitting diode, and solar cell applications. Firstly, yttria-stabilized zirconia (YSZ) and cerium dioxide (CeO2) thin films are deposited in oxygen-deficient environments; their properties are compared to those deposited in oxygen-rich environments. Oxygen-deficient films are highly (001)-oriented, which corresponds to a surface that is expected to be forbidden based on Tasker's theoretical calculation of stoichiometric ionic crystals. A model considering non-stoichiometry-induced surface relaxation and surface atomic density is proposed to explain the orientation phenomenon observed under oxygen-deficient deposition conditions. This model is consistent with previous experimental results for indium tin oxide (ITO), SnO2 and NiO thin films deposited under similar conditions. Detailed studies of the preferred orientation of these oxygen-deficient ionic crystals are of direct relevance to the fabrication of films for use in solid oxide fuel cells. Secondly, undoped, Cu-doped, Se-enriched, Cu2Se-doped, Ag-doped, Ag2Se-doped, and nitrogen-doped ZnSe films have been grown on fused quartz substrates by pulsed laser deposition. It is found that adding a small amount (~2 mol%) of Cu2Se can significantly improve crystallinity and (111) texturing of ZnSe films. While the other films are highly resistive, Cu2Se-doped ZnSe films are p-type conducting with hole concentrations of ~ cm-3 and resistivity of ~0.098 ohm*cm (compared with previous reports of ~ cm-3 and 0.75 ohm*cm, respectively). The successful heavy p-type doping of ZnSe films is attributed to substitution of Zn atoms with Cu while limiting selenium-vacancy-associated compensating defects with additional selenium. Nitrogen doping has turned ZnSe films more favorable to wurtzite structures. Two newly observed Raman peaks at 555 cm-1 and 602 cm-1 are assigned to N local vibrational modes of hexagonal ZnSe structures. The nitrogen-doped ZnSe films are not conductive, which might be due to compensating defects arising from the presence of native defects or other impurities. This work is of importance to solve doping difficulties and contact problems of wide-bandgap semiconductors. Finally, batch growth of thin films by pulsed laser deposition has been tried. Using the natural temperature gradient, films with different deposition temperatures have been fabricated together. With change of deposition temperatures, ZnSe films are shown to have problems associated with crystalline defects, selenium loss, or phase separation. ZnSe films with improved crystallinity and no phase separation have been achieved using a 16 mol% Se enriched target. Multi-plume pulsed laser deposition has been proposed and discussed. With directionality of PLD plumes and non-uniformity of PLD films, this system is supposed to be more suitable for high-throughput compound thin film fabrication, which makes it very promising for efficient materials optimization and exploration. High-throughput fabrication of compound thin films has been successfully achieved using this system.
Download or read book Development of Lead free Piezoelectric Thin Films by Pulsed Laser Deposition written by Maryam Abazari Torghabeh and published by . This book was released on 2010 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Handbook of Nanophysics written by Klaus D. Sattler and published by CRC Press. This book was released on 2010-09-17 with total page 782 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many bottom-up and top-down techniques for nanomaterial and nanostructure generation have enabled the development of applications in nanoelectronics and nanophotonics. Handbook of Nanophysics: Nanoelectronics and Nanophotonics explores important recent applications of nanophysics in the areas of electronics and photonics. Each peer-reviewed c
Download or read book Ferroelectric Thin Films IV Volume 361 written by Bruce Tuttle and published by . This book was released on 1995-08-08 with total page 658 pages. Available in PDF, EPUB and Kindle. Book excerpt: Papers from the fall 1994 symposium present research and developments from academia, government, organizations, and industry in ferroelectric thin films, organized in sections on characterization, layered structure ferroelectrics, photonic phenomena, process integration, dram thin film technology, solution deposition, and piezoelectric and IR thin film technology. Highlights include the first public technical disclosures of Y1 nonvolatile memory material. Annotation copyright by Book News, Inc., Portland, OR
Download or read book Ferroelectric Domain Walls written by Jill Guyonnet and published by Springer Science & Business Media. This book was released on 2014-04-08 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using the nano metric resolution of atomic force microscopy techniques, this work explores the rich fundamental physics and novel functionalities of domain walls in ferroelectric materials, the nano scale interfaces separating regions of differently oriented spontaneous polarization. Due to the local symmetry-breaking caused by the change in polarization, domain walls are found to possess an unexpected lateral piezoelectric response, even when this is symmetry-forbidden in the parent material. This has interesting potential applications in electromechanical devices based on ferroelectric domain patterning. Moreover, electrical conduction is shown to arise at domain walls in otherwise insulating lead zirconate titanate, the first such observation outside of multiferroic bismuth ferrite, due to the tendency of the walls to localize defects. The role of defects is then explored in the theoretical framework of disordered elastic interfaces possessing a characteristic roughness scaling and complex dynamic response. It is shown that the heterogeneous disorder landscape in ferroelectric thin films leads to a breakdown of the usual self-affine roughness, possibly related to strong pinning at individual defects. Finally, the roles of varying environmental conditions and defect densities in domain switching are explored and shown to be adequately modelled as a competition between screening effects and pinning.
