Charge Density

An analytical threshold-voltage model of short-channel undoped symmetrical double-gate metal-oxide-semiconductor field-effect transistors including positive or negative interface charges near the drain is presented. The threshold-voltage model is derived based on an analytical solution for the potential distribution along the channel in the subthreshold region. Both potential and threshold-voltage models are compared with the Atlas simulation results, with variables being the device dimensions, the interface-charge region length and the interface-charge density. A good agreement between the model and simulation results has been observed by calibrating as a constant parameter the gate voltage included in the position of the minimum potential and the carrier charge-sheet density at the potential minimum that is adequate to achieve the turn-on condition.

Gel Polymer Electrolytes (GPE) based on agar and containing LiClO4 have been prepared, characterized and applied to electrochromic devices. The ionic conductivity revealed the best result of 6.5 × 10−5 S/cm for the sample with 17 wt.% of LiClO4, which increased to 5.4 × 10−4 S/cm at 72°C. The GPE have been used in electrochromic devices (ECD) with K-glass/WO3/GPE/CeO2-TiO2/K-glass configuration. The ECD changed transmittance values up to 30% between the colored and transparent states. The charge density measurements revealed an increase of 5.5 to 7.5 mC/cm2 from the first to 500th cycles and then a decrease to 4.4 mC/cm2 during the next 4500 cycles. Coloration efficiency (η) of 25 cm2/C was obtained.

Zinc Phosphide (Zn3P2) films were deposited by vacuum evaporation under a pressure of 1.3 × 10− 5 m bar onto well-cleaned glass substrates. I–V measurements show Ohmic and non-ohmic behavior for lower and higher fields, respectively. The field-lowering coefficient was calculated theoretically and experimentally and it was found that the possible conduction mechanism in these films is Richardson–Schottky type. The activation energy decreases as the voltage increases. The zero-field activation energy was found to be 0.97 eV and this zero field activation energy decreases with an increase in film thickness. The capacitance measurements were made at room temperature. The flat band potential was found to be ∼ 1.5 V. The ionized charge density and the total number of interface states were calculated and the values were found to be 5.30 × 1016/cm3 and 4.18 × 1017 cm− 2 eV− 1 respectively.

Chirally stacked N-layer graphene systems with N >= 2 exhibit a variety of distinct broken symmetry states in which charge density contributions from different spins and valleys are spontaneously transferred between layers. We explain how these states are distinguished by their charge, spin, and valley Hall conductivities, by their orbital magnetizations, and by their edge state properties. We argue that valley Hall states have [N/2] edge channels per spin-valley.

Keywords: TMS method Comparative studies SEM images with EDS Charge density TGA/DTA analysis The organic–inorganic composite ion exchange membranes, i.e. PVC based Cu 3 (PO4) 2 and polystyrene supported Ni 3 (PO4) 2 were chemically prepared by sol–gel method. The physico-chemical nature was determined by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA) characterization. Both the membranes were found to be crystalline in nature and no sign of visible cracks is there. The theoretical value of the potential was determined by Teorell–Meyer–Sievers method, electrochemical properties were measured by potentiometer. The observed potential for both the membranes was little different and positive, the potential offered by the electrolytes was in the order of KCl > NaCl > LiCl. The transport number, mobility ratio, distribution coefficient, charge effectiveness, and the fixed charge density of the ions were calculated by potential observation. The order of surface charge density of both the membranes was found to be LiCl b NaCl b KCl.

Permeation of ions from one electrolytic solution to another, through a protein channel, is a biological process of considerable importance. Permeation occurs on a time scale of micro- to milliseconds, far longer than the femtosecond time scales of atomic motion. Direct simulations of atomic dynamics are not yet possible for such long-time scales; thus, averaging is unavoidable. The question is

Combustion simulation in two-stroke engines becomes necessary not only for engine performance prediction but also for scavenge evaluation, since in-cylinder pressure and temperature are highly influenced by combustion process evolution. Combustion simulation by using a Wiebe function is appropriate to be included in a 1D engine code for providing design criteria with fast and accurate calculations; the main drawback is the determination of the four Wiebe parameters needed to build up the in-cylinder heat release.This paper deals with a detailed methodology for heat release determination in two-stroke engines under a wide range of running conditions; obtained empirical data will serve for building ad-hoc Wiebe functions, whose four parameters will be finally correlated with engine related parameters derived from 1D simulations. Two different engines, with three exhaust systems each, varying engine speed and spark-ignition timing were used to obtain correlations far from particular situations.A multiple regression analysis stated that charge density, residual gas fraction, spark timing and mean piston speed were the significant engine parameters that influence on Wiebe parameters. Finally, two scenarios were considered regarding Wiebe parameters: (a) specific correlations different for each engine gave coefficient of multiple determination values higher than 98% when predicting indicated mean effective pressure, (b) a global correlation used for both engines provided R2 values of 93% in the 50 cc and 91% in the 125 cc engine.►Measurements for combustion characterization are obtained in 50 and 125 cc 2S engines. ►Heat release rates are reproduced by using Wiebe functions. ►Correlations for Wiebe parameters are given for small two-stroke engines. ►Correlations depend on engine parameters so phenomenological approach is attained.

The use of a passivating layer can reduce or even eliminate surface effects responsible for limiting both the RF current and breakdown voltage of AlGaN/GaN HEMTs. To study the effect of passivation on electrical characteristics of GaN-based devices, we have developed a macroscopic model of strain in SiN/AlGaN/GaN heterostructure, considering the system as a free-standing one. Basing on the strain results, we have calculated the strain map for a SiN-passivated structure and the electron sheet charge density in the channel. Results have been compared with experimental measurements and with an alternative passivation model.

More recently STM experimets present firm evidence of some kind of charge modulation in underdoped cuprates. The peculiar observations of the above experiments are located in the so called pseudo-gap region of the phase diagram, just over the superconducting-dome. The model that will be used captures in a simple way the idea that the pseudo-gap phase is formed of bound fermion pairs which are close to a CDW instability but generally do not have long range order due to quenched disorder. Thus the charge degrees of freedom will be modeled by an Ising order parameter in the presence of quenched disorder, so representing a charge glassy phase. This glassy phase will be in competition with a superconducting phase modeled by a complex order parameter. As a first step we will study the model in one dimension without disorder to familiarize with it and also to search for a possible explanation of the Giant Proximity Effect (GPE). After that we will investigate numerically the ground state properties of the 2-dimensional lattice model, focusing our attention especially on the stiffness and magnetization of the system in the xy plane. We will show that disorder can induce superconductivity in a CDW phase. This picture is really interesting because it could show how an insulating system can produce a superconducting phase thank to the interplay with impurites.

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