Search

Currently, thermal interfacial materials (TIMs) play a great role to electronic and semiconductor devices working at high voltage, power and frequency. The urgent need for electrical insulating TIMs and relevant theory are not addressed yet. This study adopted an electrical insulating [alpha]-[Si.sub.3][N.sub.4] whisker as a filler to prepare [Si.sub.3][N.sub.4w]/silicone rubber. The results show that the elongation at break and thermal conductivity of silicone rubber are promoted from 91.6% and 0.343 to 402.9% and 1.011 W [m.sup.-1] [K.sup.-1], respectively, at a filler fraction of 8.0 vol%. It reveals a multiple percolation phenomenon which has not been previously observed in an electrical insulating TIMs. The thermal percolation threshold is decreased to 4.0 vol% with increasing aspect ratio of the whisker. The behavior of the dielectric strength is explained by a double percolation model. A phonon quasi-ballistic transportation mechanism based on Coulomb interactions is proposed for the TIMs. KEYWORDS fillers, percolation, silicone rubber, thermal conductivity, [alpha]-[Si.sub.3][N.sub.4] whiskers, 1 | INTRODUCTION Currently, the great increase in the current, voltage, frequency, integration, and miniaturization of semiconductors and electronics devices and systems, such as that in electric vehicles and charge [...]

Abstract Perfect crisscross chain arrangements with high inter-chain H-bonding structure of conjugated polyamides are capable of inter-chain proton transfer and this property of conjugated polyamides makes them semiconducting material. To [...]

Excitonic insulators (EIs) arise from the formation of bound electron-hole pairs (excitons).sup.1,2 in semiconductors and provide a solid-state platform for quantum many-boson physics.sup.3-8. Strong exciton-exciton repulsion is expected to stabilize condensed superfluid and crystalline phases by suppressing both density and phase fluctuations.sup.8-11. Although spectroscopic signatures of EIs have been reported.sup.6,12-14, conclusive evidence for strongly correlated EI states has remained elusive. Here we demonstrate a strongly correlated two-dimensional (2D) EI ground state formed in transition metal dichalcogenide (TMD) semiconductor double layers. A quasi-equilibrium spatially indirect exciton fluid is created when the bias voltage applied between the two electrically isolated TMD layers is tuned to a range that populates bound electron-hole pairs, but not free electrons or holes.sup.15-17. Capacitance measurements show that the fluid is exciton-compressible but charge-incompressible--direct thermodynamic evidence of the EI. The fluid is also strongly correlated with a dimensionless exciton coupling constant exceeding 10. We construct an exciton phase diagram that reveals both the Mott transition and interaction-stabilized quasi-condensation. Our experiment paves the path for realizing exotic quantum phases of excitons.sup.8, as well as multi-terminal exciton circuitry for applications.sup.18-20. So far only signatures of excitonic insulators have been reported, but here direct thermodynamic evidence is provided for a strongly correlated excitonic insulating state in transition metal dichalcogenide semiconductor double layers., Author(s): Liguo Ma [sup.1] , Phuong X. Nguyen [sup.1] , Zefang Wang [sup.1] , Yongxin Zeng [sup.2] , Kenji Watanabe [sup.3] , Takashi Taniguchi [sup.3] , Allan H. MacDonald [sup.2] [...]

We review the material properties that allowed amorphous silicon to become the dominant large area semiconductor and then point out how amorphous oxide semiconductors could displace a-Si in thin film transistors, and how phase change materials, such as GeSbTe alloys, have provided an optical storage technology and will provide a nonvolatile electrical storage technology based on their unique properties. PACS Nos.: 71.15.Mb, 71.23.Cq, 73.61.Jc. Nous passons en revue les proprietes du silicium amorphe qui lui ont permis de devenir un joueur si dominant dans les semi-conducteurs et nous soulignons comment les oxydes de semi-conducteurs amorphes pourraient remplacer a-Si dans les transistors en films minces et comment les materiaux a changement de phase, tel l'alliage GeSbTe, peuvent nous donner une technologie de stockage optique et nous fournir une technologie de stockage electrique non volatile, a cause de leurs uniques proprietes. [Traduit par la Redaction], Introduction This paper reviews the properties and usefulness of amorphous silicon (a-Si) versus other contender amorphous semiconductors over the history of the ICANS conference. Early ICANS conferences focused on the [...]

A highly sensitive competitive immunosensor based on the electrochemiluminescence (ECL) of quantum dots (QDs) was proposed by coupling with an enzymatic amplification. The fabrication process of the immunosensor was traced with atomic force microscopic images and electrochemical impedance spectra. The strong cathodic ECL emission of the immobilized QDs could be detected at a relatively low emission potential. The reduction of dissolved oxygen during the cathodic process provided a self-produced coreactant, [H.sub.2][O.sub.2], for the ECL emission. Using human IgG (HIgG) as a model protein, upon the immuno-recognition of the immobilized HIgG to its antibody labeled simply with horseradish peroxidase, the ECL intensity decreased due to the steric hindrance of the proteins to electron Iransfer. The decrease could be greatly amplified by an enzymatic cycle to consume the self-produced coreactant, leading to a wide calibration range of 0.05 ng [mL.sup.-1] ~ 5 [micro]g [mL.sup.-1] and a low limit of detection for the competitive immunoassay of HIgG. This immunosensor showed good stability and fabrication reproducibility. The immunoassays of practical samples showed acceptable results. This facile immunosensing strategy opened a new avenue for detection of proteins and application of QDs in ECL biosensing. 10.1021/ac1013942

Impurity-based p-type doping in wide--band-gap semiconductors is inefficient at room temperature for applications such as lasers because the positive-charge carriers (holes) have a large thermal activation energy. We demonstrate high-efficiency p-type doping by ionizing acceptor dopants using the built-in electronic polarization in bulk uniaxial semiconductor crystals. Because the mobile hole gases are field-ionized, they are robust to thermal freezeout effects and lead to major improvements in p-type electrical conductivity. The new doping technique results in improved optical emission efficiency in prototype ultraviolet light-emitting--diode structures. Polarization-induced doping provides an attractive solution to both p- and n-type doping problems in wide--band-gap semiconductors and offers an unconventional path for the development of solid-state deep-ultraviolet optoelectronic devices and wide--band-gap bipolar electronic devices of the future. 10.1126/science.1183226

Several mathematical models have been developed and tested to determine the impact of the generation volume on the different profiles of the electron beam-induced current (EBIC). A complete comparative analysis of the different models is also presented.

The article presents and examines a new physical model, which is employed to demonstrate the impact of structural relaxation (SR) of the chalcogenide materials on the reliability of phase-change memory (PCM) cells. The defect annihilation dynamics is also shown to be highly affected by the electrical characteristics of the cells.

The concept of using the threshold-voltage shift in disordered-semiconductor-based thin-film transistors is described to measure the time of occurrence of randomly spaced events of interest. The studies have shown that the analog clock very accurate while, at the same time, is very simple in design by using just one transistor.

An eight-band k*p model is used to calculate the electronic structure of highly scaled InSb and InAs nanowire (NW) field-effect transistors (FETs). The results from the analytical expressions for the transconductance, cutoff frequency, and gate delay time revealed that the gate delay times strongly depend on the drive current.

The advances in chemically synthesized semiconductor nanowires used as nanoelectronic devices and the basic nanowire field-effect transistor structures for both p- and n-channel homogeneous composition nanowires are reviewed. The application of thin-film nanowire transistor arrays on low-cost substrates for relatively high-frequency ring oscillators and completely transparent device arrays are discussed.

The current transportation mechanism of Hf[O.sub.2] gate dielectrics with a TaN metal gate and silicon surface fluorine implantation is examined. Effective trapping levels at 1.25 eV below the HfOF conduction band are observed.

A self-consistent extraction method is presented for coplanar waveguide (CPW) probed AlGaN high-electron mobility transistors (HEMTs). Findings reveal the achievement of consistent results for both small- and large periphery AlGaN HEMTs.

The performance of multi-walled carbon nanotube (MWCNT)-based interconnect is evaluated. Findings reveal the achievement of small signal delay at the intermediate and global levels.

The article explains an analytical equation, which has recently been developed for the charge collection from within a collecting junction well. The relationship between charge collected and other parameters of the collecting junction well is also studied.

The current-voltage (I-V) characteristics under forward biases obtained in small size (In, Ga)N-GaN multiquantum-well diodes are discussed. Findings reveal the capability of the diodes in detecting optical powers in the pW range under barrier illumination.

Electronic transport through II-VI semiconductors resonant-tunneling structures containing diluted magnetic impurities is demonstrated. A giant Zeeman splitting in the presence of a moderately low magnetic field arises due to the exchange interaction between the conduction electrons and the impurities and experimental data that are presented shows that devices can work as spin filters when the quantum well is magnetic.

The various injection contact technologies that are reported are summarized and their potential for practice device applications in terms of electrical efficiency is assessed. The results demonstrate that the key requirement to observe a significant magnetoresistence is a correct design of the semiconductor channel such that the spin polarization that is provided by the magnetic contacts can be preserved.

The finite element analysis was employed to study the steady current field distribution under the configuration of four point probe method for resistivity measurement in a diamond anvil cell (DAC). It was found that the finite size of the electrode could lead to significant errors in resistivity measurement for semiconducting samples and the probe spacing is a key factor in the resistivity measurement accuracy for samples in DAC.

The importance of the electrocrystallization approach in constructing and precisely controlling the morphology and stoichiometry of Co[[TCNQ].sub.2] (TCNQ = tetracyanoquinodimethane) based materials is presented. The findings show that the electrocrystallization process occurs through two distinctly different, potential-dependent nucleation-growth mechanisms.

The thermoelectric power factor of a nanoporous matrix material is investigated. The results have shown that the use of a good thermoelectric material instead of a dielectric as the matrix for thermoelectric nanocomposites might enhance the overall nanocomposite's power factor and might also be advantageous for power generation applications, where the main aim is to maximize the generated power.

The complex permittivity and resistivity of float-zone high-resistivity silicon were measured at microwave frequencies for temperatures from 10 up to 400 K employing dielectric-resonator and composite dielectric-resonator techniques. At temperatures below 25 K, where all free carriers are frozen out, loss-tangent values of the order of 2 x [10.sup.-4] were measured, suggesting the existence of hopping conductivity or surface charge carrier conductivity in this temperature range. Use of a composite dielectric-resonator technique enabled the measurement of materials having higher dielectric losses (or lower resistivities) with respect to the dielectric-resonator technique. The real part of permittivity of silicon proved to be frequency independent. Dielectric losses of high-resistivity silicon at microwave frequencies are mainly associated with conductivity and their behavior versus temperature can be satisfactory described by dc conductivity models, except at very low temperatures. Index Terms--Conductivity measurement, dielectric losses, dielectric resonators, permittivity measurement, silicon, semiconductor materials measurements.

We describe the results of a photocapacitance study of Metal-Insulator-Semiconductor (MIS) capacitors formed from semiconducting polymers. In this technique, capacitance-voltage (C-V) plots of the devices are obtained prior, during and after illumination with light of energy greater than the optical band gap of the semiconductor. When the capacitors are biased into depletion and simultaneously exposed to light, optically-generated minority electrons drift to and become trapped in states at the semiconductor-insulator interface, resulting in a significant shift of the C-V plot to more positive voltages. For devices employing a polysilsesquioxane insulator clear and unambiguous evidence is obtained for the formation of an inversion layer at the interface. Upon terminating the illumination, the devices relax back to the initially-obtained dark C-V plots as the trapped electrons are thermally excited from their trapping states. By tracking the voltage required to maintain a constant capacitance the dynamics of charge detrapping can be followed leading to an estimate for the energy of the interface state. Index Terms--Polymer electronics, MIS capacitors, photocapacitance, interface states.

A numerical model is described for the calculation of the opto-electronic properties of a semiconductor InAs-InAlGaAs quantum dash active material including the presence of wetting layer (WL) and the quantum mechanical coupling among dashes. The results reveal that WL plays a role in limiting the gain performance such as the maximum gain, the differential gain and the optical gain bandwidth.

The method for extracting the concentration and mobility of electrons and holes in semiconductor layers by making a rational polynomial fit to the conductivity tensor is described. It is shown that how to fit the conductivity tensor to a rational polynomial function of the magnetic field and how to find an inverse Laplace and fourier transformation from a partial fraction expansion of the rational polynomial fit.

The effect of aggregation on surfactant-suspended individual single-walled carbon nanotubes (SWNT) Raman spectroscopy was explored in the context of dielectrophoretic separation. Aggregation plays an important role in the apparent metallic to semiconductor SWNT ratios and can compromise conclusions based on Raman alone and must be combined with additional analytical method such as electrical characterization, chemical reactivity and absorption spectroscopy to qualify the efficacy of SWNT separation.

The optical absorption of GaAs nanorings under dc and ac electric fields with frequency at the tetrahertz range applied in the plane containing the nanoring is investigated. The applied lateral electric fields change the optical absorption spectra prominently and in the presence of tetrahertz electric fields, the optical spectra may be very different for diferent frequencies.

The influence of doping on the process of charge injection from a metal electrode into a model organic semiconductor is investigated. It was observed that the contact resistance, which was relevant figure of merit, was found to decrease dramatically upon doping beyond what is expected from theory and is seen in crystalline semiconductors.

Two representative methods, namely free carrier absorption and laser deflection measurements, are theoretically investigated. A consistent evaluation rule for extracting carrier and temperature gradients from the detector signals of deflection measurements is derived.

The study reports on the reproducible performance of single ZnO nanowire field-effect transistors (FETs) in standard global back-gate geometry. It describes a dynamic gate effect that seems to involve mobile surface charges and causes hysteresis in the transconductance, among other effects.

A proposition of a self-coordinated model of kinetics formation of electrostatic contrast in a corona discharge is done. Details of this model that takes into consideration a nonlinearity of current-voltage characteristics of the semiconductor, and thermoplastic and deformation of the thermoplastic layer are discussed.

This paper evaluates the electric stress enhancement due to surface protrusions on the tape of semiconductive shield compounds used in power cables. The results of a conventional grade and a supersmooth grade shield compounds are reported. Using a laser-scanning instrument, the shape of protrusions on the tape surface of these compounds can be quantitatively determined. An algorithm is developed to portray the geometry of a protrusion so as to allow the calculation of its stress enhancement. First the supersmooth grade shield compound is illustrated as much smoother than the conventional shield compound. Besides exhibiting a lower number of protrusions, the surface protrusions on a supersmooth shield compound also are much 'flatter' than those of the conventional shield compounds. Insulation thickness is confirmed to influence the stress enhancement and, consequently, different distributions of stress enhancement factor are observed with low voltage, say, 15 kV, and high voltage, say, 500 kV, applications. The conventional shield compound exhibits higher stress enhancement than the supersmooth grade compound in higher voltage cables, though the difference is much less with lower voltage settings. Since the total number of protrusions on the conventional shield surface is more than one order of magnitude higher, the supersmooth shield therefore can offer much better protection to a cable by minimizing the electric stress degradation in its insulation material. Index Terms--Electric stress enhancement, semiconductive shields, conventional grades, supersmooth grade, surface smoothness measurement, surface protrusions, quality control, quality assurance testing.

Silicon carbide (SiC) is an attractive semiconductor material for high-power electronic devices. The differences in the electrical properties between the experimental data and expected values are discussed.