Showing papers on "Dielectric published in 2000"
TL;DR: In this article, the dielectric properties of isostructural compounds of the type A 2/3 Cu 3 Ti 4 O 12 (A =trivalent rare earth or Bi) have been presented.
1,825 citations
TL;DR: It is shown that a large piezoelectric response can be driven by polarization rotation induced by an external electric field, and the computations suggest how to design materials with better performance, and may stimulate further interest in the fundamental theory of dielectric systems in finite electric fields.
Abstract: Piezoelectric materials, which convert mechanical to electrical energy (and vice versa), are crucial in medical imaging, telecommunication and ultrasonic devices. A new generation of single-crystal materials, such as Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) and Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), exhibit a piezoelectric effect that is ten times larger than conventional ceramics, and may revolutionize these applications. However, the mechanism underlying the ultrahigh performance of these new materials-and consequently the possibilities for further improvements-are not at present clear. Here we report a first-principles study of the ferroelectric perovskite, BaTiO3, which is similar to single-crystal PZN-PT but is a simpler system to analyse. We show that a large piezoelectric response can be driven by polarization rotation induced by an external electric field. Our computations suggest how to design materials with better performance, and may stimulate further interest in the fundamental theory of dielectric systems in finite electric fields.
1,789 citations
TL;DR: In this paper, the authors describe a material, cubic CaCu 3 Ti 4 O 12, which exhibits a large dielectric response, the temperature-dependence of which has not been seen, to our knowledge, in any existing material.
1,006 citations
TL;DR: In this article, a gate dielectric film with metal contents ranging from ∼3 to 30 at. % Hf and Zr has been investigated, and the results show that Hf exhibits excellent electrical properties and high thermal stability in direct contact with Si, while Al electrodes produce very good electrical properties, but also react with the silicates.
Abstract: Hafnium and zirconium silicate (HfSixOy and ZrSixOy, respectively) gate dielectric films with metal contents ranging from ∼3 to 30 at. % Hf, or 2 to 27 at. % Zr (±1 at. % for Hf and Zr, respectively, within a given film), have been investigated, and films with ∼2–8 at. % Hf or Zr exhibit excellent electrical properties and high thermal stability in direct contact with Si. Capacitance–voltage measurements show an equivalent oxide thickness tox of about 18 A (21 A) for a 50 A HfSixOy (50 A ZrSixOy) film deposited directly on a Si substrate. Current–voltage measurements show for the same films a leakage current of less than 2×10−6 A/cm2 at 1.0 V bias. Hysteresis in these films is measured to be less than 10 mV, the breakdown field is measured to be EBD∼10 MV/cm, and the midgap interface state density is estimated to be Dit∼1–5×1011 cm−2 eV−1. Au electrodes produce excellent electrical properties, while Al electrodes produce very good electrical results, but also react with the silicates, creating a lower e l...
1,001 citations
15 Aug 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the graphite die set in a spark plasma system (SPS) is heated by a pulse direct current, which induces good effects on materials in the die.
Abstract: The graphite die set in spark plasma system (SPS) is heated by a pulse direct current. Weak plasma, discharge impact, electric field and electric current, which are based on this current, induce good effects on materials in the die. The surface films of aluminum and pure WC powders are ruptured by the spark plasma. Pure AlN powder is sintered without sintering additives in the electric field. The spark plasma leaves discharge patterns on insulators. Organic fibers are etched by the spark plasma. Thermosetting polyimide is consolidated by the spark plasma. Insoluble polymonomethylsilane is rearranged into the soluble one by the spark plasma. A single crystal of CoSb3 is grown from the compound powders in the electric field by slow heating. Coupled crystals of eutectic powder are connected with each other in the electric field.
953 citations
TL;DR: In this paper, an electric-field assisted assembly technique was used to position individual nanowires suspended in a dielectric medium between two electrodes defined lithographically on a SiO2 substrate.
Abstract: This letter describes an electric-field assisted assembly technique used to position individual nanowires suspended in a dielectric medium between two electrodes defined lithographically on a SiO2 substrate. During the assembly process, the forces that induce alignment are a result of nanowire polarization in the applied alternating electric field. This alignment approach has facilitated rapid electrical characterization of 350- and 70-nm-diameter Au nanowires, which had room-temperature resistivities of approximately 2.9 and 4.5×10−6 Ω cm.
933 citations
858 citations
TL;DR: In this paper, the dispersion of the electromagnetic modes with film thickness and width has been assessed and the effects caused by varying the difference between the superstrate and substrate dielectric constants on the characteristics of the modes have been determined.
Abstract: The purely bound electromagnetic modes of propagation supported by asymmetric waveguide structures, comprised of a thin lossy metal film of finite width on a dielectric substrate and covered by a different dielectric superstrate, have been characterized at optical wavelengths. The dispersion of the modes with film thickness and width has been assessed and the effects caused by varying the difference between the superstrate and substrate dielectric constants on the characteristics of the modes have been determined. The modes are quite different from those supported by corresponding slab structures or similar finite-width symmetric waveguides. Unlike these limiting cases, the dispersion with film thickness can exhibit an unusual oscillatory character which is explained by a switching or swapping of the constituent interface modes. In addition, the four fundamental modes supported can evolve such that none has a diminishing attenuation with diminishing film thickness. This rather complex evolution of modes is unique to asymmetric finite-width structures. Under certain conditions, a long-ranging mode having a field distribution that is suitable to excitation using an end-fire technique can be supported. The long-ranging mode has a cutoff thickness below which it is no longer propagated, and its attenuation near cutoff decreases very rapidly, much more so than the attenuation related to the long-ranging mode in a comparable symmetric waveguide. Furthermore, its cutoff thickness is larger than that of the ${s}_{b}$ mode in the corresponding asymmetric slab waveguide, which implies that decreasing the film width increases the sensitivity of the mode to the asymmetry in the structure. This result is interesting and potentially useful in that the propagation characteristics of the mode can be affected by a smaller change in the dielectric constant of the substrate or superstrate compared with the ${s}_{b}$ mode guided by the corresponding slab structure.
835 citations
TL;DR: In this article, a nonlinear, high-strain, Mooney-Rivlin model was used to determine the expected strain response for a given applied field pressure, and it was determined that the electrostatic forces between the free charges on the electrodes are responsible for the observed response.
737 citations
TL;DR: A simple electrostatic technique is reported that creates and replicates lateral structures in polymer films on a submicrometre length scale, based on the fact that dielectric media experience a force in an electric field gradient.
Abstract: The wavelength of light represents a fundamental technological barrier to the production of increasingly smaller features on integrated circuits. New technologies that allow the replication of patterns on scales less than 100 nm need to be developed if increases in computing power are to continue at the present rate. Here we report a simple electrostatic technique that creates and replicates lateral structures in polymer films on a submicrometre length scale. Our method is based on the fact that dielectric media experience a force in an electric field gradient. Strong field gradients can produce forces that overcome the surface tension in thin liquid films, inducing an instability that features a characteristic hexagonal order. In our experiments, pattern formation takes place in polymer films at elevated temperatures, and is fixed by cooling the sample to room temperature. The application of a laterally varying electric field causes the instability to be focused in the direction of the highest electric field. This results in the replication of a topographically structured electrode. We report patterns with lateral dimensions of 140 nm, but the extension of the technique to pattern replication on scales smaller than 100 nm seems feasible.
734 citations
TL;DR: In this article, a ceramic-powder polymer composite, making use of a relaxor ferroelectric polymer that has a high room-temperature dielectric constant as the matrix, is developed.
Abstract: A ceramic-powder polymer composite, making use of a relaxor ferroelectric polymer that has a high room-temperature dielectric constant as the matrix, is developed. The experimental data show that the dielectric constant of the composites with Pb(Mg1/3Nb2/3)O3–PbTiO3 powders can reach more than 250 with weak temperature dependence. In addition, the composites under a proper preparation procedure exhibit a high breakdown field strength (>120 MV/m), leading to a maximum energy storage density of more than 15 J/cm3. Experimental results also indicate that the high electron irradiation does not have much effect on the dielectric behavior of Pb(Mg1/3Nb2/3)O3–PbTiO3 powders, possibly due to the relaxor nature of the ceramic.
TL;DR: In this article, the dielectric properties of ultrathin hafnium oxide reoxidized with rapid thermal annealing (RTA) have been investigated and the leakage current was found to be less than 3×10−2 ǫA/cm2 at −1.5 V (i.e., ∼2 V below VFB).
Abstract: Dielectric properties of ultrathin hafnium oxide reoxidized with rapid thermal annealing (RTA) have been investigated. Capacitance equivalent oxide thickness (CET) of 45 A hafnium oxide was scaled down to ∼10 A with a leakage current less than 3×10−2 A/cm2 at −1.5 V (i.e., ∼2 V below VFB). Leakage current increase due to crystallization was not observed even after 900 °C rapid thermal annealing (RTA), but CET did increase after high temperature RTA due to the interfacial layer growth and possible silicate formation in the HfO2 film.
15 Aug 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a molecular orbital model is proposed to predict the behavior of pure materials in a microwave field, and experimental work as well as dielectric property measurements confirm the accuracy of this model in specific cases.
Abstract: Microwave energy (microwave frequency, in this case, includes radio frequencies and ranges from 0.3 MHz to 300 GHz) is being developed as a new tool for high-temperature processing of materials. Examples of the advantages associated with microwave processing include: rapid and uniform heating; decreased sintering temperatures; improved physical and mechanical properties; and, unique properties which are not observed in conventional processes. These advantages observed in materials processed using microwave energy are being attributed to ‘microwave effects’ which are particular to this technology. Researchers at the University of Florida are working to identify and to qualitatively and quantitatively define the mechanisms of microwave–material interactions. A new model has been developed based on the molecular orbital model which predicts the behavior of specific pure materials in a microwave field. Experimental work as well as dielectric property measurements confirm the accuracy of this model in specific cases.
TL;DR: In this paper, a self-consistent two-dimensional modeling of the temporal and spatial development of a microdischarge and discharge step is investigated numerically, and the results lead to an understanding of the dynamics of DBDs.
Abstract: Dielectric barrier discharges (DBDs) occur in configurations which are characterized by a dielectric layer between conducting electrodes. Two basic configurations can be distinguished: a volume discharge (VD) arrangement with a gas gap; and a surface discharge (SD) arrangement with surface electrode(s) on a dielectric layer and an extensive counter electrode on its reverse side. At atmospheric pressure the DBD consists of numerous microdischarges (VD) and discharge steps (SD), respectively, their number being proportional to the amplitude of the voltage. These events have a short duration in the range of some 10 ns transferring a certain amount of charge within the discharge region. The total transferred charge determines the current and hence the volt-ampere characteristic of each arrangement. The microdischarges (discharge steps) have a complicated spatial structure. The discharge patterns on the dielectric surface depend on the polarity and amplitude of the applied voltage as well as on the specific capacity of the dielectric. Experimental findings on DBDs in air and oxygen are presented and discussed. On the basis of a self-consistent two-dimensional modelling the temporal and spatial development of a microdischarge and discharge step are investigated numerically. The results lead to an understanding of the dynamics of DBDs. Although in VD arrangements cathode-directed streamers appear especially in electronegative gases, their appearance is rather unlikely in SD arrangements. The application of DBDs for plasma-chemical reactions is determined by the productivity, with which the energy of the electric field can be converted into internal states of atoms and/or molecules. Depending on the desired product it could be both the generation of internal electronic states of molecules or atoms and dissociation products of molecules. The discharge current and current density of DBDs in both the SD and VD arrangements as well as the energy release and energy density distribution in the discharge region are presented. As an example the effectiveness of the energy conversion into ozone production is detailed. Some peculiarities of the discharge parameters, for instance the correlation between discharge patterns (microdischarges or discharge steps) and surface charge density, are discussed.
TL;DR: A review of the literature on size effects in ferroelectric materials, with an emphasis on thin film perovskite ferroelectrics, can be found in this paper.
Abstract: ▪ Abstract This paper reviews the literature on size effects in ferroelectric materials, with an emphasis on thin film perovskite ferroelectrics. The roles of boundary conditions, defect chemistry, electrode interfaces, surface layers, and microstructure in controlling the measured properties of ferroelectric films, as well as the observed deviation from bulk properties are discussed. Examples of the manifestation of size effects in terms of the low and high field dielectric properties, the piezoelectric effect, and the leakage behavior of films are given.
TL;DR: Inorganic solids with wide bandgaps are usually classified as electrical insulators and are used in industry as insulators, dielectrics, and optical materials as mentioned in this paper, however, interest in these wide-gap oxides as conductive materials has not been strong.
Abstract: Inorganic solids with wide bandgaps are usually classified as electrical insulators and are used in industry as insulators, dielectrics, and optical materials. Many metallic oxides have wide bandgaps because of the significant contribution of ionic character to the chemical bonds between metallic cations and oxide ions. Their ionic nature simultaneously suppresses the formation of easily ionizable shallow donors or acceptors and enhances the localization of electrons and positive holes. Thus it is understandable that interest in these wide-gap oxides as conductive materials has not been strong.
TL;DR: The glass transitionTemperature T(g) and the temperature T(alpha) corresponding to the peak in the dielectric loss due to the alpha process have been simultaneously determined as functions of film thickness d through dielectrics measurements for polystyrene thin films supported on glass substrate.
Abstract: The glass transition temperature T(g) and the temperature T(alpha) corresponding to the peak in the dielectric loss due to the alpha process have been simultaneously determined as functions of film thickness d through dielectric measurements for polystyrene thin films supported on glass substrate. The dielectric loss peaks have also been investigated as functions of frequency for a given temperature. A decrease in T(g) was observed with decreasing film thickness, while T(alpha) was found to remain almost constant for d>d(c) and to decrease drastically with decreasing d for d
TL;DR: In this article, the determination of effective dielectric properties of hetereogeneous materials, in particular media with lossy constituents that have complex permittivity parameters, is discussed.
Abstract: This article discusses the determination of effective dielectric properties of hetereogeneous materials, in particular media with lossy constituents that have complex permittivity parameters. Several different accepted mixing rules are presented and the effects of the structure and internal geometry of the mixture on the effective permittivity are illustrated. Special attention is paid to phenomena that the mixing process causes in the character of the macroscopic dielectric response of the mixture when the losses of one or several of the components are high or when there is a strong dielectric contrast between the component permittivities.
TL;DR: SiLK resin this article is a solution of a low-molecular-weight aromatic thermosetting polymer, which is used in the fabrication of interconnect structures such as the one shown in the Figure.
Abstract: For faster, smaller, and higher performance integrated circuits, a low dielectric constant insulator is required to replace silicon dioxide. Here the properties of a new dielectric—SiLK resin, a solution of a low-molecular-weight aromatic thermosetting polymer—are reviewed and examples of its application in the fabrication of interconnect structures, such as the one shown in the Figure, are given.
TL;DR: In this article, a review of the general requirements for process integration and material properties of low-k dielectrics are discussed, focusing on the challenge in developing materials with low dielectric constant but strong thermomechanical properties.
Abstract: ▪ Abstract As integrated circuit (IC) dimensions continue to decrease, RC delay, crosstalk noise, and power dissipation of the interconnect structure become limiting factors for ultra-large-scale integration of integrated circuits. Materials with low dielectric constant are being developed to replace silicon dioxide as interlevel dielectrics. In this review, the general requirements for process integration and material properties of low-k dielectrics are first discussed. The discussion is focused on the challenge in developing materials with low dielectric constant but strong thermomechanical properties. This is followed by a description of the material characterization techniques, including several recently developed for porous materials. Finally, the material characteristics of candidate low-k dielectrics will be discussed to illustrate their structure-property relations.
TL;DR: The absorption dipole orientation of single fluorescent molecules is determined by mapping the spatial distribution of the squared electric field components in a high-numerical-aperture laser focus and holds promise to monitor rotational diffusion of single molecules in complex environments.
Abstract: The absorption dipole orientation of single fluorescent molecules is determined by mapping the spatial distribution of the squared electric field components in a high-numerical-aperture laser focus. Annular illumination geometry and the vicinity of a plane dielectric/air interface strongly enhance the longitudinal field component and the transverse fields perpendicular to the polarization direction. As a result, all three excitation field components in the focus are of comparable magnitude. The scheme holds promise to monitor rotational diffusion of single molecules in complex environments.
Patent•
29 Nov 2000TL;DR: In this paper, a method of forming an interlayer dielectric on a semiconductor device is disclosed, where a phosphorous doped oxide layer is deposited on the semiconductor devices to fill gaps and provide phosphorous for gettering.
Abstract: A method of forming an interlayer dielectric on a semiconductor device is disclosed. First, a phosphorous doped oxide layer is deposited on the semiconductor device to fill gaps and provide phosphorous for gettering. Then, an undoped oxide layer is deposited and planarized using chemical mechanical polishing (CMP). The undoped oxide layer is denser than the phosphorous doped oxide layer, so the undoped oxide layer can be polished more uniformly than the phosphorous doped oxide layer and can serve as a polish stop for a subsequent tungsten plug polish. Also, the denser undoped oxide layer serves as a more effective moisture barrier than the doped oxide layer. Overall fabrication process complexity can be reduced by performing both oxide depositions in a single operation with no intervening densification or CMP steps.
TL;DR: In this paper, the authors demonstrate an equivalent oxide thickness of about 21 A for a 50 A ZrSixOy film sputterdeposited directly on a Si substrate, as measured by capacitance-voltage techniques, with a hysteresis shift less than 10 mV.
Abstract: Zirconium silicate (ZrSixOy) gate dielectric films with ∼3–5 at. % Zr exhibit excellent electrical properties and high thermal stability in direct contact with Si. We demonstrate an equivalent oxide thickness of about 21 A for a 50 A ZrSixOy film sputter-deposited directly on a Si substrate, as measured by capacitance–voltage techniques, with a hysteresis shift less than 10 mV. Leakage currents for these films are very low, approximately 1×10−6 A/cm2 at 1.0 V bias in accumulation. Films ramped to hard breakdown exhibit breakdown fields Ebd ∼10 MV/cm. Excellent electrical properties are obtained with Au electrodes, in particular.
TL;DR: The present paper reports the results of an extensive numerical analysis of electromagnetic fields in random dielectric materials, and shows how the effective permittivity of a mixture with random inclusion positionings is distributed.
Abstract: The present paper reports the results of an extensive numerical analysis of electromagnetic fields in random dielectric materials. The effective permittivity of a two-dimensional (2-D) dielectric mixture is calculated by FDTD simulations of such a sample in a TEM waveguide. Various theoretical bounds are tested in light of the numerical simulations. The results show how the effective permittivity of a mixture with random inclusion positionings is distributed. All possible permittivity values lie between Wiener limits, and according to FDTD simulations the values are almost always between Hashin-Shtrikman limits. Calculated permittivity distribution is also compared with theoretical mixture models. No model seems to be able to predict the simulated behavior over the whole range of volume fraction.
TL;DR: In this article, the electrical characteristics of SiOx/ZrO2 and Si Ox/Ta2O5 gate dielectric stacks were investigated and the current density was shown to be strongly temperature dependent at low voltage (below about 2 V).
Abstract: The electrical characteristics of SiOx/ZrO2 and SiOx/Ta2O5 gate dielectric stacks are investigated. The current–density JG in these dielectric stacks is shown to be strongly temperature dependent at low voltage (below about 2 V), the more so in the ZrO2 stack. On the other hand, JG is much less temperature dependent at higher voltage. These results are consistent with a model which takes into account the direct tunneling of electrons across the SiOx layer and the trap-assisted tunneling of electrons through traps with energy levels below the conduction band of the high permittivity dielectric layer. The energy levels and densities of these electron trapping centers are estimated by fitting this trap-assisted tunneling model to the experimental results.
TL;DR: SrTiO3 has been grown epitaxially by molecular beam epitaxy on Si The capacitance of this 110 A dielectric film is electrically equivalent to less than 10 A of SiO2 This structure has been used to make capacitors and metal oxide semiconductor field effect transistors as discussed by the authors.
Abstract: SrTiO3 has been grown epitaxially by molecular beam epitaxy on Si The capacitance of this 110 A dielectric film is electrically equivalent to less than 10 A of SiO2 This structure has been used to make capacitors and metal oxide semiconductor field effect transistors The interface trap density between the SrTiO3 and the Si is 64×1010 states/cm2 eV and the inversion layer mobility is 221 and 62 cm2/V s for n- and p-channel devices, respectively The gate leakage in these devices is two orders of magnitude smaller than a similar SiO2 gate dielectric field effect transistor
TL;DR: In the crystallographic structure of the V66E mutant, a chain of water molecules was seen that hydrates the buried Glu-66 and links it with bulk solvent, providing compelling and unprecedented experimental evidence that solvent penetration can contribute significantly to the high apparent polarizability inside proteins.
TL;DR: An all-dielectric coaxial waveguide that can overcome problems of polarization rotation and pulse broadening in the transmission of optical light is presented here.
Abstract: An all-dielectric coaxial waveguide that can overcome problems of polarization rotation and pulse broadening in the transmission of optical light is presented here. It consists of a coaxial waveguiding region with a low index of refraction, bounded by two cylindrical, dielectric, multilayer, omnidirectional reflecting mirrors. The waveguide can be designed to support a single mode whose properties are very similar to the unique transverse electromagnetic mode of a traditional metallic coaxial cable. The new mode has radial symmetry and a point of zero dispersion. Moreover, because the light is not confined by total internal reflection, the waveguide can guide light around very sharp corners.
TL;DR: In this article, the pump-probe signals near the plasmon resonance of the nanoparticles reveal the importance of electron-electron scattering during several hundreds of femtoseconds.
TL;DR: In this article, the application of new dielectric materials with μ, ϵ, and low loss to antennas is investigated, and a zero-order analysis reveals the advantages and limitations of these materials for patch antennas.
Abstract: The application of new dielectric materials with μ, ϵ, and low loss to antennas is investigated. A zero-order analysis reveals the advantages and limitations of these materials for patch antennas. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26, 75–78, 2000.