Geometric current component in charge-pumping measurements

A semi-analytical-model is proposed to predict the geometric component in charge pumping (CP) measurements for transistors. It is based on contributing of active CP-area and low-level voltage (V L ) of the gate signal, thermal diffusion, drift field, and self-induced drift field. The calculated I CP -V L characteristics with geometric component model are found in good correlation with the experimental I CP -V L data and are more accurate than the calculated CP without geometric component. This modeling approach can be extended for MOSFET stress reliability evaluation such as negative bias temperature instability (NBTI) and radiation degradations.

In this paper, we study the interface traps during program/erase (P/E) cycles. By using charge pumping measurement, the charge pumping currents (ICP) of the serial P/E cycled states are compared to the initial one. The ICP decreases after the programmed operation under a constant temperature within 5 P/E cycles. The observation on the recovery of the interface states has been attributed to the hot electron injection stress.

Evaluation of energy recovery potential of solar thermoelectric generators using a three-dimensional transient numerical model

A numerical study on the diffusiophoresis of a droplet in an electrolyte medium is carried out by solving the full set of coupled governing equations, which are based on the conservation principle. Diffusiophoresis is considered for monovalent as well as non-z:z electrolytes and mixed electrolytes. The numerical model is supplemented with a semianalytic simplified model based on first-order perturbation analysis, which agrees with the numerical model for a low to moderate range of surface potential. The mobility for a low-viscosity fluid at a thinner Debye length is dominated by the chemiphoresis part, which creates the mobility to become an even function of the surface charge density for a monovalent electrolyte. Such a pattern in mobility does not appear in a non-z:z asymmetric electrolyte. At a thinner Debye length, diffusiophoresis becomes independent of the diffusion field, hence the mobility is independent of the composition of electrolytes in a mixed monovalent electrolyte solution. Our results show that the size-based sorting of droplets is efficient when a mixed electrolyte is considered. We have also addressed the finite ion size effects by considering a modified ion transport equation. One of the key features of the present study is the simplified semianalytical model for the diffusiophoresis of a droplet in a z:z electrolyte as well as in non-z:z and mixed electrolytes, which is shown to be valid up to a moderate range of surface potential for a finite Debye length.

This study presents several one-dimensional mathematical models derived to simulate the distribution of radionuclides in soil overlying uranium ore deposits. The migration of gaseous products away from the ore is simulated by mechanisms of molecular diffusion and advective transport. A homogeneous overburden containing no uranium or radium is assumed throughout. The study is intended to be a first step in analyzing the feasibility of detecting uranium ore by remote geochemical measurements. A steady-state diffusion model predicts the detectability of radon-222 and some of its daughter products several tens of meters from a uranium deposit. In reality this range would be shortened by the masking effect of radon generated in the overlying soil itself. Krypton-85 is found to be only marginally detectable even in the immediate vicinity of the ore. Xenon-133 would be detectable at half the range of /sup 222/Rn. The effect of soil gas motion as an additional transport mechanism is evaluated using both steady-state and transient models. A constant soil gas velocity of 1 x 10/sup -4/ cm/sec causes gaseous radioisotope activities to change by several orders of magnitude. Detectability of uranium could be significantly increased if long-term soil gas motion is confirmed. A transient numerical model is used to simulate barometric influences on the migration of /sup 222/Rn away from an ore deposit. It was found that near-surface effects are +-15% which would not appreciably affect the detectability of uranium by geochemical means.

The impacts of the gate length and width of the transistors on the single event upset (SEU) hardness of static random access memory (SRAM) cells has been investigated by SPICE simulations, biased on a partially depleted (PD) silicon-on-insulator (SOI) CMOS technology. The results show that increasing the gate width can dramatically enhance the linear energy transfer (LET) threshold of SEU, as compared with increasing the gate length. A new parameter, unit gate area LET threshold, is introduced for characterizing the change in efficiency of improving the SEU resistance with increasing the gate length and width of the transistors in a cell. The effect of decoupling capacitors on cell SEU LET threshold is also presented by making a comparison with that of the transistors with increased gate lengths.

Predicting wellbore dynamics in a steam-assisted gravity drainage system: Numeric and semi-analytic model, and validation

An analytical and experimental investigation has been performed to determine the thermal behavior of two glass-filled, decomposing polymer composites. A one-dimensional, transient numerical model has been developed to predict the overall thermally-induced response of these materials, without including the idealized assumption of local-thermal equilibrium. For both materials, the expansion characteristics and volumetric heat transfer coefficients were experimentally determined for input into the numerical model. The results of the numerical study with a prescribed surface heat flux of 279.7 kW/m$\\sp2$ indicate that local-thermal equilibrium does not exist in either H41N or MXBE-350. In fact, solid to gas temperature differences of 500$\\sp\\circ$C exist locally for MXBE-350. While for the tighter, more fibrous H41N differences as high as 200$\\sp\\circ$C are predicted locally for the times investigated. For H41N, pressures in excess of 10 atmospheres were predicted, and the existence of such high pressures has been verified experimentally. An investigation into the effects of the idealized assumption of local-thermal equilibrium revealed significant errors associated with the assumption for both materials. Solid temperature differences between the actual and idealized cases were as high as 100$\\sp\\circ$C and 180$\\sp\\circ$C locally for H41N and MXBE-350, respectively. As a result, measurable errors are evident in the mass loss and pressure profiles for the idealized case. The errors in the pressure and mass loss profiles are significant because spallation and/or cracking are highly dependent on stress concentration and material strength, which are linked to internal pressure and stage of decomposition, respectively. From the results of this study, it is evident that accurate numerical modeling can only be achieved when the idealized assumption of local-thermal equilibrium is not incorporated into the modeling scheme.

We have investigated the thermal degradation of oxide TFT with various gate length and width under various gate and drain voltages by using an infrared imaging system. An asymmetrical thermal distribution was observed at a local drain region in a TFT depending on bias stress. Threshold voltage shift was observed with stress time depending on the gate width. We discussed the degradation mechanism by analyzing the electrical properties and thermal distribution. We considered that the degradation phenomena are caused by a combination of Joule heating and the hot carrier effect. This model was confirmed by theoretical device simulation.

In the application of pulsating heat pipes (PHPs), the lengths of the adiabatic sections are usually determined by the distance between the heat source and the heat sink, and have important effects on the performance of PHPs. However, there was little research on the effect of the adiabatic section lengths on the performance of PHPs. In this work, a new transient numerical model was proposed to investigate the transient flow and the heat transfer for PHPs with various adiabatic section lengths of 60, 120, 180, and 240 mm. Based on the numerical results, the flow and the heat transfer characteristics of the PHPs were analyzed. It was found that the flow velocities in the PHP with different adiabatic lengths increased with the increase in the heat input, and the mean velocity was calculated to be in the range of 0.139–0.428 m/s, which was consistent with the previous experimental results. The start-up performance of the PHP was better with shorter adiabatic section length. Furthermore, the thermal resistances of the PHPs with different adiabatic section lengths were calculated to analyze the effects of the adiabatic section length on the performance of the PHP. The results showed that when the heat input was 20 W, the PHP with the adiabatic section of 60 mm showed the lowest thermal resistance, whereas the PHP with longer adiabatic section length presented lower thermal resistance at high heat input (≥25 W).

A simulator for calculating MESFET large-signal figures of merit and their sensitivities with respect to various device design, material and operational parameters has been developed. A study of an ion-implanted device with a 0.42- mu m gate length and 1.0-mm gate width is presented. The effects on maximum power-added efficiency, output power at the maximum power-added efficiency, and output power at 1-dB gain compression due to variation in implant peak doping density, implant range, implant straggle, gate length, gate width, and gate-drain breakdown voltage are presented. The data indicate that the device performance is most sensitive to changes in V/sub gdbd/ for values of V/sub gdbd/ less than 20 V. However, performance sensitivity goes to zero for V/sub gdbd/ greater than 20 V. RF performance is also sensitive to changes in the channel implant parameters. However, the simulated sensitivities are less than those for V/sub gdbd/. Over fairly broad ranges, device performance is less sensitive to changes in L/sub g/ and W/sub g/ but degrades rapidly at the extrema. >

A multi-gate n-type In0.53Ga0.47As MOSFET is fabricated using gate-first self-aligned method and air-bridge technology. The devices with different gate lengths were fabricated with the Al2O3 oxide layer with the thickness of 8 nm. In this letter, impact of gate length variation on device parameter such as threshold voltage, high and low voltage transconductance, subthreshold swing and off current are investigated at room temperature. Scaling the gate length revealed good enhancement in all investigated parameters but the negative shift in threshold voltage was observed for shorter gate lengths. The high drain current of 1.13 A/mm and maximum extrinsic transconductance of 678 mS/mm with the field effect mobility of 364 cm2/Vs are achieved for the gate length and width of 0.2 µm and 30µm, respectively. The source/drain overlap length for the device is approximately extracted about 51 nm with the leakage current in order of 10−8 A. The results of RF measurement for cut-off and maximum oscillation frequency for devices with different gate lengths are compared.

Research on thermochemical erosion and thermal protection properties of multiple interface nozzles in long-time working hybrid rocket motors

Heat transfer beneath ice-rink floors

Based on the Magneto-Hydro-Dynamic (MHD) theory, a united three-dimensional (3D) transient numerical model is developed to investigate the dynamic behaviors of arc plasma for a magnesium alloy AZ61A gas tungsten arc welding (GTAW) arc. The arc, electrode and workpiece are integrated into one calculation domain to avoid both presumed distribution of the current density at the electrode tip and the assumption of constant conditions of interface between welding arc and workpiece. The distributions of electric potential, current density, magnetic flux density, electromagnetic force, velocity, temperature, and pressure of the arc plasma in the 3D space are analyzed by using the numerical model. Results indicate that the maximum gradient of the electric potential in the whole arc space exists around the electrode tip, where the electric current density, electromagnetic force, and temperature are also the maximum. However, maximum pressure is found at the velocity stagnation, which is above the workpiece. Comparison between predicted temperature and measured one in arc region shows a good agreement.