摘要:

Ferroic crystals have domain walls which can be moved by electric field (ferroelectrics), magnetic fields (ferromagnets), mechanical stress (ferroelastics) or a higher order phenomenon involving a combination of the three (secondary ferroics). Because of the large contribution movable domain walls make to piezoelectricity, permittivity, permeability, and to elastic compliance, these materials are used as transducers, capacitors, transformers, sensors and actuators. A basic understanding of size effects is critical to the development of these devices, which are being made in smaller and smaller sizes in the form of thin films, fiber-filled composites, and multilayer ceramics with submicron grain sizes.

ISSN:1058-4587    

DOI:10.1080/10584589808238761

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A brief review is given of ferroelectric thin-film memory technology, emphasizing up-to-date comparisons among different materials, including lead zirconate-titanate (PZT), barium-strontium titanate (BST), and strontium bismuth tantalate (SBT) for both DRAMS and non-volatile RAMS.

ISSN:1058-4587    

DOI:10.1080/10584589808238762

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Numerous epitaxial LiNbO3films,i.e., LiNbO3(0001)/Al2O3(0001), LiNbO3(0001)/Al2O3(1120), and LiNbO3(1120)/Al2O3(1120) films, were grown by pulsed laser deposition. Low deposition temperatures below 450°C were used in order to reduce a Li deficient phase, LiNb3O8. Structural properties of the films, including twin formation, were investigated by X-ray -2 scan and pole figure techniques. Nonlinear optical properties of these films were investigated using the Marker fringe and the Senarmont methods. The nonlinear optical coefficients related to the SHG,i.e., d31andd33, were measured and their values were found to be very close to the LiNbO3single crystal values. It was also found that the SHG -scan can provide information on twin formations and in-plane orientation of the film. Electro-optic (EO) properties of the films were also studied. Films with different orientations display large differences in their EO properties: the epitaxial LiNbO3(0001) films show little EO effects, but the LiNbO3(1120) film shows a large quadratic EO behavior with an effective coefficient of 2.38×10×15m2/V2.

ISSN:1058-4587    

DOI:10.1080/10584589808238763

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Ferroelectric (FE) thin films have been widely studied, especially for their electrical and ferroelectric properties, such as nonvolatile FE memory and ultrahigh density DRAMs. FE films also give rise to a variety of interesting and unique optical applications, such as electro-optic switches, passive and active waveguides, second harmonic generation, optical data storage, optical diodes and photovoltaic devices. Their dielectric properties have been extensively optimized but the optical and electro-optical aspects have not been satisfactorily explored. This paper will review the latest advances in the optical and electro-optical properties of FE films, highlighted by data obtained from our laboratories. Optical (refractive index and waveguiding loss) and electro-optical (linear (r33) and quadratic (R33) electro-optic coefficients) properties will be presented. Optimization of these properties by precise tailoring of chemistry, processing conditions and microstructure is discussed. Low optical loss,i.e., < 2dB/cm and an exceptionally highr33value of 315pm/V from PLZT films were obtained.

ISSN:1058-4587    

DOI:10.1080/10584589808238764

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Thin films of ferroelectric materials of PbTiO3, Pb(Zr, Ti)O3, BaTiO3and TiO2-xwere prepared by metalorganic chemical vapor deposition (MOCVD) on various substrates of SrTiO3, fused silica glass, p-Si, p-InSb, n-InP, p-GaAs, indium tin oxide-coated soda lime glass, Pt/Ti/SiO2/Si, RuO2/SiO2/Si and Pt/RuO2/SiO2/Si substrates. Low temperature growth at substrate temperature below 500°C of dielectric/ferroelectric thin films viain-situMOCVD process was carried out to study structural and electrical properties.

ISSN:1058-4587    

DOI:10.1080/10584589808238765

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The oxide class in general includes an enormous number of compounds with widely ranging properties. Study of oxide hetero-structures promises to lead to both new areas of physics research and new generation of devices. However, the growth of oxide thin films presents some unique challenges due to the presence of large number of phases present in the phase diagrams. Epitaxial thin films of various ferroelectric perovskite-type oxides have been successfully grown using the metalorganic chemical vapor deposition (MOCVD) technique. The design of MOCVD processes and equipment requires great care. In this talk, MOCVD growth strategies will be presented largely by using numerical models, which can simulate the complicated fluid mechanics and mass transfer taking place in the reaction chamber. The equilibrium and the dynamical properties of epitaxial ferroelectric thin films have been predicted by using a theory based on a free-energy functional of the Landau-Ginzburg-Devonshire type. Good agreement between the predictions of this model and the experimental results was obtained for thickness-dependent properties such as the relative domain population, spontaneous strain and coercive field.

ISSN:1058-4587    

DOI:10.1080/10584589808238766

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this talk we treat domain patterns that develop in epitaxial ferroelectric (FE) films. The models are applicable to ferroelectric films grown epitaxially in their paraelectric cubic state (PE) on single crystal substrates. We explicitly treat misfit strain relaxation by both misfit dislocations and by domain pattern formation. We have developed temperature dependent stability maps that predict the energetically favorable domain structure that will form at the PE → FE transition. The stability maps incorporate the role of: (i) the substrate lattice parameter; (ii) differential thermal expansion; (iii) cooling rate; (iv) depolarizing fields and electrode geometry; and (v) applied electric fields. We treat the formal defect description both the …a1/a2/a1/a2… and the …a1/c/a1/c… domain patterns and show rigorous mechanics solutions for the elastic energy of both configurations. As a result of the PE → FE transition, the crystal axes of individual domain are rotated in the far-field. The concepts of the domain stability map, the relative coherency strain, and far field rotation of crystals axes in the domain are verified by three independent measurements (integrated x-ray peak intensity, partitioning of crystals tilts, and domain volume fraction by TEM) for MOCVD PbTiO3films grown on MgO(001), SrTiO3(001), LaAlO3(001) and SrRuO3/SrTiO3(001).

ISSN:1058-4587    

DOI:10.1080/10584589808238767

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Over the past five years extensive research and development efforts have conclusively proven that perovskite metallic oxide (e.g., La-Sr-Co-O) contacts to PZT thin films yields excellent ferroelectric properties and reliability including fatigue and imprint free capacitors. Currently, our effort is focused on process integration approaches to grow the LSCO/PNZT/LSCO capacitors on top of a poly-Si plug with conducting barrier layers, lowering the operating voltage from 5V to 2.5V and understanding the microscopic details of imprint and fatigue phenomena in ferroelectric capacitors. In collaboration with researchers at Sandia National Laboratories, Radiant Technologies, Virginia Tech. and Raytheon, a robust high density Ferroelectric RAM process is being developed. These research efforts have provided us with a comprehensive understanding of the origins of imprint and fatigue within the framework of a novel process that yields robust capacitors with switched polarization values in the range of 15–25 μC/cm2(for an operating voltage of 3–5V). In this presentation we will present an overview of our progress in these areas.

ISSN:1058-4587    

DOI:10.1080/10584589808238768

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Ferroelectric thin films have been receiving great attention for the applications in emerging areas. The MOD(Metal-Organic Deposition) processing could be successfully applied for processing the well controlled epitaxial ferroelectric films at relatively low temperatures. Examples are K(Ta, Nb)O3and LiNbO3film processings. Epitaxial films of K(Ta, Nb)O3could be synthesized by the reaction control of metal alkoxides on Pt(100)/MgO(100) substrates. The structures of the precursor solutions were analyzed to control the crystallization. The chemically modified metal alkoxide precursor with a chelate ligand could be utilized for micro-patterned LiNbO3epitaxial films using ultra-violet irradiation. The combination of micro-patterning will afford the novel break-through to the development of the integrated functional materials.

ISSN:1058-4587    

DOI:10.1080/10584589808238769

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this paper, we report the preparation and characteristics of Ca and La doped PbTiO3(PCLT) thin film on Pt/Ti/SiO2/Si substrate by laser ablating a ceramic/metal target. The deposited film is polycrystalline and exhibits good ferroelectric hysteresis loop, low leakage, and good pyroelectric properties. The pyroelectric coefficient of the film is high as 8.81 × 10×8C/cm2K and the effective dielectric constant of the film is about 352. So the figure of merit of the film is high as 0.78 × 10×10Ccm/J, indicating that PCLT is a promising material for pyroelectric application.

ISSN:1058-4587    

DOI:10.1080/10584589808238770

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor