Variation Of Dielectric Research Articles

Crystallization Kinetics Study on Orthogonal Ordering in N-(p-n-Alkyoxybenzylidene)-p-n-Alkylanilines (nO.m Compounds) by Thermal and Electrical Techniques. Part I

A systematic kinetic study of crystallization among two smectogens of higher homologues of the benzylidene aniline series nO.m, viz. 4O.12 and 8O.12, has been carried out by thermal microscopy, differential scanning calorimetry (DSC), and dielectric studies. The crystallization kinetics was studied by two techniques, viz. the traditional thermal analysis, i. e. DSC, and electrical studies, i. e. capacitance and dielectric loss variation measurements with temperature. The DSC thermograms were run from the crystallization temperature to the isotropic melting temperature for different time intervals. The liquid crystalline behaviour together with the rate of crystallization of smectic ordering in newly synthesized nO.m compounds were discussed in relation to the kinetophase (which occurs prior to crystallization). The molecular mechanism and dimensionality of crystal growth were computed using the Avrami equation. The characteristic crystallization time (t∗) at each crystallization temperature was deduced from the individual plots of logtand ΔH. Further, it was observed that the data obtained from DSC and dielectric studies were in good agreement.

Damage Detection of FRP-Strengthened Concrete Structures Using Capacitance Measurements

In this study, a new concept for detecting air voids, water intrusion, and glue infiltration damages in fiber-reinforced polymers (FRPs)-strengthened concrete structures was developed. The concept, based on detecting the local dielectric permittivity variations, was employed to design coplanar capacitance sensors (CCSs) to detect such defects. An analytical model was used to introduce the sensor operation theory and analyze the influence of different sensor parameters on the output signals and to optimize sensor design. Two dimensional finite element (FE) simulations were performed to assess the validity of the analytical results and to evaluate other sensor design-related parameters. To experimentally verify the FE model, dielectric properties of various materials involved in FRP-strengthened concrete systems were measured. In addition, two concrete specimens strengthened with FRP laminates and containing preinduced defects were constructed and inspected in a laboratory setting. Good agreement was found ...

Study of gate dielectric permittivity variation with different equivalent oxide thickness on channel engineered deep sub-micrometer n-MOSFET device for mixed signal applications

The impact of high permittivity gate dielectrics with different equivalent oxide thickness (EOT) for conventional, low and high tilt angle halo implants on the performance of 100 nm n-MOSFETs device is studied using device simulator Synopsys ISE-TCAD. In this paper, we systematically increase the value of gate dielectric (3.9–50) and investigate its effects on conventional, low angle of tilt (10 o) and high angle of tilt (50 o) halo implants for different device parameters of 100 nm n-MOSFETs using two different EOT viz. 1.5 nm and 2.0 nm. The impact of gate dielectric permittivity along with the different angles of halo implants on short channel performance contributing to the DIBL, the subthreshold swing, I ON/ I OFF ratio, and the threshold voltage V T are studied for two different EOT thicknesses. The device has been investigated for digital performance parameters like the variation of substrate–body voltage on DIBL, I OFF, I ON and the threshold voltage V T for sub 100 nm technology generation. It has also been investigated for analog performance like trans-conductance generation factor (gm/ I D) and overall gain (gm R 0).

Ionic conductivity by correlated barrier hopping in NH4I doped chitosan solid electrolyte

Abstract Chitosan–NH 4 I and chitosan–NH 4 I–EC films have been prepared by solution cast technique. The sample containing 45 wt% ammonium iodide (NH 4 I) exhibited the highest room temperature conductivity of 3.7×10 −7 S cm −1 . The conductivity of the sample increased to 7.6×10 −6 S cm −1 when 40 wt% ethylene carbonate (EC) was added to the 55 wt% chitosan-45 wt% NH 4 I sample. The conductivity–temperature relationship is Arrhenian. From dielectric loss variation with frequency, the power law exponent was obtained. The temperature dependence of the power law exponent for chitosan–NH 4 I system follows the correlated barrier hopping (CBH) model while conduction mechanism of the plasticized system can be represented by the small polaron hopping (SPH) model.

Crystallization kinetics study on tilted ordering in N-(p-n-alkyoxybenzylidene)-p-n-alkylanilines (nO.m compounds) by thermal and electrical techniques. Part I

Abstract A systematic kinetic study of crystallization among two smectogens of higher homologues of the benzylidene aniline nO.m series viz. 15O.12 and 15O.16 has been carried out by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and dielectric studies. The crystallization kinetics was studied by two techniques viz. the traditional thermal analysis (DSC) and dielectric technique viz. capacitance and dielectric loss variation with temperature. The DSC thermograms were run from crystallization temperature to the isotropic melt for different time intervals. The liquid crystalline behaviour together with the rate of crystallization of smectic ordering in newly synthesized nO.m compounds were discussed in relation to the kinetophase (which occurs prior to the crystallization). The molecular mechanism and dimensionality in the crystal growth were computed from the Avrami equation. The characteristic crystallization time (t*) at each crystallization temperature was deduced from the individual plots of log t and ΔH. Further, it was observed that the data obtained from DSC, POM and dielectric studies were in good agreement with one another.

Crystallization Kinetics Study on Tilted Ordering in N-(p-n-Alkoxybenzylidene)-p-n-Alkylanilines (nO·m Compounds) by Thermal and Electrical Techniques Part II

A systematic kinetic study of crystallization among two smectogens of higher homologues of the benzylideneaniline nO·m series viz 15O.8 and 15O.10 has been carried out by thermal microscopy, differential scanning calorimetry (DSC), and dielectric studies. The crystallization kinetics was studied by two techniques viz the traditional thermal analysis (DSC) and electrical studies viz capacitance and dielectric loss variation with temperature. The DSC thermograms were run from crystallization temperature to the isotropic melt for different time intervals. The liquid crystalline behavior together with the rate of crystallization of smectic ordering in newly synthesized nO·m compounds were discussed in relation to the kinetophase (which occurs prior to the crystallization). The molecular mechanism and dimensionality in the crystal growth were computed from the Avrami equation. The characteristic crystallization time (t*) at each crystallization temperature was deduced from the individual plots of log t and ΔH. Further, it was observed that the data obtained from DSC and dielectric studies were in good agreement with one another.

Planar infrared binary phase reflectarray

A reflective, binary phase reflectarray is demonstrated in the infrared, at a wavelength of 10.6 microm. The unique aspect of this work, at this frequency band, is that the specific desired phase shift is achieved using an array of subwavelength metallic patches on top of a ground-plane-backed dielectric stand-off layer. This is an alternative to the usual method of constructing a reflective Fresnel zone plate by means of a given thickness of dielectric. This initial demonstration of the reflectarray approach at infrared is significant in that there is inherent flexibility to create a range of phase shifts by varying the dimensions of the patches. This will allow for a multilevel phase distribution, or even a continuous variation of phase, across an optical surface with only two-dimensional lithography, avoiding the need for dielectric height variations.

Study of the relaxor behavior in BaTi 1− xHf xO 3 (0.20 ≤ x ≤ 0.30) ceramics

The influence of Hf doping on the structure and dielectric properties of BaTiO 3 has been studied. For this purpose Ba(Ti 1− x Hf x )O 3 ceramics were prepared through solid-state reaction route at close compositions, having x = 0.20, 0.22, 0.23 and 0.30. The study was aimed to locate the exact hafnium concentration for normal to relaxor crossover in these ceramics. X-ray diffraction followed by Rietveld refinement, reveals the formation of single phase with Pm3 m cubic structure. Temperature and frequency dependence of real ( ɛ′) and imaginary ( ɛ″) parts of the dielectric permittivity have been studied in the temperature range of 90–350 K, at frequencies between 0.1 kHz and 100 kHz. The dielectric permittivity variations with temperature show deviation from Curie–Weiss behavior and strong frequency dispersion. The deviation from Curie–Weiss behavior, discontinuous jump along with the change in the slope of T m vs Hf concentration plot, and the degree of relaxation ( γ) approaching ∼2, indicate a crossover from normal to relaxor ferroelectrics. Substitution of Hf 4+ for Ti 4+ in BaTiO 3 introduces structural disorder, causing perturbations like local electric and strain fields. These perturbations reduce the long-range polar order resulting in relaxor behavior.

Properties of microcavities in two-dimensional photonic quasicrystals with octagonal rotational symmetry

It is now well established that two-dimensional structures with dielectric variations based on quasicrystalline tilings are able to support photonic band gaps. Here, we have investigated the properties of the localized defect modes with frequencies within the photonic band gap for a certain kind of two-dimensional octagonal photonic quasicrystal with lattice vacancies breaking the quasi-periodic symmetry. The eigenfrequencies of such localized modes are given as a function of filling fractions for four distinct microcavity designs, and the electromagnetic field profiles of the localized modes are explored. The calculations of the eigenfrequencies and electromagnetic field profiles were performed using a supercell approximation in a plane wave method.

Study of the influence of the dielectric layer thickness in a CNT-FED

An experimental investigation is carried out to study the influences of the dielectric layer thickness variation on the field emission characteristics and luminance distribution in a CNT-FED fabricated by screen-printing. Two steps are contained in the investigation: (1) the dielectric layer thickness fluctuations are presented with an ultrasonic thickness gauge, and (2) a simulation model is constructed to study the corresponding influences of the dielectric layer thickness fluctuations on the field emission characteristics and luminance uniformity on the screen. Our findings indicate that the dielectric layer thickness fluctuations are mainly larger than 5 μm, which mean the dielectric layer thickness fluctuation is an important cause of the non-uniform luminance distribution according to the analysis results from our simulation model. From the simulation results, we also determine the tolerance of the dielectric layer thickness in a CNT-FED to achieve uniform luminance and spot size on the screen.

Supercooled water relaxation dynamics probed with heterodyne transient grating experiments

We report results from a heterodyne-detected transient grating experiment on liquid and supercooled water in a wide temperature range, from -17.5 to 90 degrees C. The measured signal covers an extremely large time window with an excellent signal-to-noise ratio that enables the investigation in a single experiment of the sound speed and attenuation, thermal diffusivity, and temperature dependence of the dielectric constant. The experimental data clearly show the effect of the density and the temperature fluctuations on the water dielectric function. In order to describe the experimental results, we introduce a comprehensive hydrodynamic model taking into account the coupled density and temperature variables and their relevance in the definition of the spontaneous and forced dielectric variations. We use this model to describe the measured signal in transient grating experiments, including the heating and the electrostrictive sources produced by the laser excitation. The fitting procedure enables the safe extraction of several dynamic properties of liquid and supercooled water: the sound velocity and its damping, the thermal diffusivity, and the ratio between the dielectric thermodynamic derivatives. The measured parameters are compared to the literature data and discussed in the complex scenario of water physics.

Semiempirical Electromagnetic Modeling of Crack Detection and Sizing in Cement-Based Materials Using Near-Field Microwave Methods

Detection and characterization of cracks in cement-based materials is an integral part of damage evaluation for health monitoring of civil structures. Microwave signals are able to penetrate inside of dielectric materials (e.g., cement-based materials) and are sensitive to local, physical, geometrical, and dielectric variations in a structure. This makes microwave nondestructive testing and evaluation (NDT&E) techniques suitable for inspection and health monitoring of civil structures. Near-field microwave NDT&E techniques offer the added advantage of providing high spatial resolution, requiring simple hardware that may be portable, low power, fast, real time, and robust. Additionally, these techniques are noncontact and one-sided. Besides the need for robust detection, electromagnetic modeling of a microwave probe response to a crack is also an important issue. Such a model can be used to obtain optimal measurement parameters and serve as the foundation for extracting important crack information such as its width and depth. In this paper, the utility of open-ended rectangular waveguide probes for detecting surface-breaking cracks in cement-based materials is discussed. Subsequently, the development of a semiempirical model capable of simulating the crack response is presented. The model described here translates the magnitude and phase of the reflection coefficient as a function of scanning distance into the complex reflection plane and takes advantage of the common shape of these signals for predicting a similar signal from an unknown crack. Finally, this empirical model is used to estimate crack dimensions from a set of measurements.

SLOT-LINE FERROELECTRIC PHASE-SHIFTERS AND PHASE-ARRAY ANTENNA ON THEIR BASE

ABSTRACT The experimental characteristics of the microwave phase-shifter based on the slot-line including ferroelectric film are presented. The tuning of the microwave signal phase at the slot-line output was provided due to the ferroelectric film dielectric permittivity variations under the DC control voltage application across the line slot. Phase shifter tested served as a basis for the 8-elemetns phase array antenna. The scanning sector of the steerable antenna was 60 deg and beam width was 13 deg.

Water molecule clusters measured at water/air interfaces using atomic force microscopy

During the tip approach to hydrophobic surfaces like the water/air interface, the measured interaction force reveals a strong attraction with a range of approximately 250 nm at some points along the interface. The range of this force is approximately 100 times larger than the measured for gold (approximately 3 nm) and 10 times larger than the one for hydrophobic silicon surfaces (approximately 25 nm). At other points the interface exerts a medium range repulsive force growing stepwise as the tip approaches the interface plane, consequently the hydrophobic force is a strong function of position. To explain these results we propose a model where the force on the tip is associated with the exchange of a small volume of the interface with a dielectric permittivity epsilon(int) by the tip with a dielectric permittivity epsilon(tip). By assuming a oscillatory spatial dependence for the dielectric permittivity it is possible to fit the measured force profiles. This dielectric spatial variation was associated with the orientation of the water molecules arrangement in the interfacial region. Small nanosized hydrogen-bond connected cages of water molecules present in bulk water at the interface are oriented by the interfacial electric field generated by the water molecules broken bonds, one broken hydrogen bond out of every four. This interfacial field orients small clusters formed by approximately 100 water molecules into larger clusters (approximately 100 nm). In the limit of small (less than 5 nm thick) water molecule cages we have modeled the static dielectric permittivity (epsilon) as the average response of those cages. In these regions the dielectric permittivity for water/air interfaces decreases monotonically from the bulk value epsilon approximately 80 to approximately 2 at the interface. For regions filled with medium size cages, the tip senses the structure of each cage and the static dielectric permittivity is matched to the geometrical features of these cages sized approximately 25 to 40 nm. Interfacial electric energy density values were calculated using the electric field intensity and the dielectric permittivity obtained by the fitting of the experimental points. The integration of the electric energy density along the interfacial region gives a value of 0.072 J m(-2) for interfacial energy density for points where the hydrophobic force has a range of approximately 250 nm. Regions formed by various clusters result in lower values of the interfacial energy density.

Scalability and Electrical Properties of Germanium Oxynitride MOS Dielectrics

In this letter, we present a fundamental study on the scalability and electrical properties of germanium oxynitride dielectrics for metal-oxide-semiconductor device applications. The nitrogen depth profile within the oxynitride dielectric layers was first monitored using angle-resolved x-ray photoemission spectroscopy and the dielectric permittivity variation was therefore identified. After thinning down the lower permittivity portion of these dielectrics, we successfully scaled down the capacitance-based equivalent SiO/sub 2/ thickness, in Ge MOS capacitors, to 1.9 nm without suffering from gate leakage. We have also investigated the effects of thermal annealing on various capacitor electrical properties. For instance, we measured a flat-band voltage shift of as much as -0.8 V from the ideal value on as-deposited capacitors and the recovery of the theoretical value, with acceptably small amount of oxide fixed charge, after subsequent thermal annealing. Lastly, we have benchmarked the performance of these oxynitride insulators with the advanced high-/spl kappa/ dielectrics on Ge and discussed the impacts on future scaling.

Synthesis and characterization of PLZT thin films obtained by pulsed laser deposition

Thin films of Pb1-xLax(Zr0.65Ti0.35)1-x/4O3 with x=0.09 (PLZT 9/65/35) have been grown by pulsed laser deposition (PLD) and by PLD assisted by radio frequency (RF) discharge in oxygen which increases the plasma reactivity and reduces the oxygen vacancies in films and at the film-bottom electrode interface. Significant compositional, structural and dielectric differences have been found among samples grown in the same deposition conditions excepting for RF power. Films grown by RF-assisted PLD have less pyrochlore and are more oriented. For these films dielectric permittivity vs. temperature variation was typical of relaxor ferroelectrics and the temperature of the dielectric maximum was close to that obtained in bulk, but the permittivity value was much lower. This was attributed mainly to the influence of a low permittivity interface layer and to the detrimental effect of pyrochlore phase, still present in small quantities even in the films obtained by RF-PLD. The dielectric behavior of films grown without RF discharge was very different: no dielectric anomaly was observed, only a step increase above 180 °C. Moreover much higher dielectric loss was measured for these films.

Rapid Method to Account for Process Variation in Full-Chip Capacitance Extraction

Full-chip capacitance extraction programs based on lookup techniques, such as HILEX/CUP , can be enhanced to rigorously account for process variations in the dimensions of very large scale integration interconnect wires with only modest additional computational effort. HILEX/CUP extracts interconnect capacitance from layout using analytical models with reasonable accuracy. These extracted capacitances are strictly valid only for the nominal interconnect dimensions; the networked nature of capacitive relationships in dense, complex interconnect structures precludes simple extrapolations of capacitance with dimensional changes. However, the derivatives, with respect to linewidth variation of the analytical models, can be accumulated along with the capacitance itself for each interacting pair of nodes. A numerically computed derivative with respect to metal and dielectric layer thickness variation can also be accumulated. Each node pair's extracted capacitance and its gradient with respect to linewidth and thickness variation on each metal and dielectric layer can be stored in a file. Thus, instead of storing a scalar value for each extracted capacitance, a vector of 3I+1 values will be stored for capacitance and its gradient, where I is the number of metal layers. Subsequently, this gradient information can be used during circuit simulation in conjunction with any arbitrary vector of interconnect process variations to perform sensitivity analysis of circuit performance.

Transient grating experiment on supercooled water

We measured the acoustic and thermal relaxation dynamics on supercooled water in the temperature range from 42 to −17°C by heterodyne-detected transient grating (TG) experiments. The TG signal shows some particular and interesting features that are produced by the anomalous behaviour of the thermodynamic parameters of water. In particular, the thermal diffusion effects disappear in the TG data for a temperature of about 0°C. We found that this effect has to be ascribed to the combination of two different physical phenomena: the anomalous temperature dependence of water density and the contribution to the TG signal from the dielectric variation induced directly by the temperature. This term is usually neglected in both light scattering and TG studies; our data show clearly a non-negligible thermal decay that has to be addressed. The data are analysed using a model based on a simple formulation of the linearized hydrodynamic equations. A Markovian approximation for the memory function is used, since the structural relaxation times are much faster than the other responses analysed.

Simultaneous surface acoustic wave and surface plasmon resonance measurements: Electrodeposition and biological interactions monitoring

We present results from an instrument combining surface acoustic wave propagation and surface plasmon resonance measurements. The objective is to use two independent methods, the former based on adsorbed mass change measurements and the latter on surface dielectric properties variations, to identify physical properties of protein layers, and more specifically their water content. We display mass sensitivity calibration curves using electrodeposition of copper leading to a sensitivity in liquid of 150±15 cm2/g for the Love mode device used here, and the application to monitoring biological processes. The extraction of protein layer thickness and protein to water content ratio is also presented for S-layer proteins under investigation. We obtain, respectively, 4.7±0.7 nm and 75±15%.

Semiconductor Dopant Profile and Dielectric Characterization with Scanning Capacitance Microscopy

ABSTRACTScanning capacitance microscopy (SCM) has been commonly used to image dopant gradients in silicon and other semiconductors. As a mobile, high-resolution (to 10 nm) metal-oxide-semiconductor (MOS) probe, SCM also is a non-destructive, contactless tool with which to examine local variations in dielectric thin film quality and local variations in semiconductor substrate properties. Virtually any measurement that can be made with fabricated metal electrodes can also be made with SCM. Two particular applications being pursued are characterization of high-κ dielectric films on silicon for next generation integrated circuits and characterization of native and deposited insulators on wide bandgap semiconductors.Local differential capacitance (ΔC) versus tip bias (Vdc) measurements can be made with SCM using an ac voltage to generate the differential capacitance signal. These measurements differ from conventional C-V measurements due to the 3-D nature of the scanning capacitance microscope tip and the method used to generate the differential capacitance signal. Theoretical predictions and experimental measurements are made of SCM differential capacitance versus dc bias voltage (ΔC-V) curves for MOS capacitors with various levels of fixed and interface traps. The goal of this work is to determine if quantitative interface trap distributions can be made using SCM and if variations in interface density can be observed near defects or device structures. The response of the SCM MOS capacitance measurement to a local electric field stress and optical pumping from the atomic force microscope (AFM) laser will also be discussed.