Analysis Of Field-effect Transistors Research Articles

Enhanced Thermopower of Saturated Molecules by Noncovalent Anchor-Induced Electron Doping of Single-Layer Graphene Electrode.

Enhancing thermopower is a key goal in organic and molecular thermoelectrics. Herein, it is shown that introducing noncovalent contact with a single-layer graphene (SLG) electrode improves the thermopower of saturated molecules as compared to the traditional gold-thiolate covalent contact. Thermoelectric junction measurements with a liquid-metal technique reveal that the value of Seebeck coefficient in large-area junctions based on n-alkylamine self-assembled monolayers (SAMs) on SLG is increased up to fivefold compared to the analogous junction based on n-alkanethiolate SAMs on gold. Experiments with Raman spectroscopy and field-effect transistor analysis indicate that such enhancements benefit from the creation of new in-gap states and electron doping through noncovalent interaction between the amine anchor and the SLG electrode, which leads to a reduced energy offset between the Fermi level and the transport channel. This work demonstrates that control of interfacial bonding nature in molecular junctions improves the Seebeck effect in saturated molecules.

Modelo compacto con capacidad de predicción de parámetros físicos para amplificadores de RF

En el presente trabajo se ha presentado un análisis de transistores de efecto de campo usando fuentes de voltaje pulsadas. Se han realizado medidas de microondas en dispositivos de tecnología HEMT’s y LDMOS poniendo en evidencia la diferencia entre el comportamiento estático y dinámico de dichos dispositivos. En base a las medidas se ha realizado un procesamiento de datos derivando una nueva ecuación con la capacidad de reproducir ambos tipos de comportamiento con elevada precisión y en diferentes puntos de operación. Consecuentemente el trabajo aporta un nuevo modelo basado en un circuito no lineal de cuatro terminales. La relevancia de este modelo es la capacidad de predecir los efectos físicos como la dispersión frecuencial y la movilidad electrónica del dispositivo semiconductor. Esto es importante pues la dispersión frecuencial es uno de los problemas más importantes de los sistemas de comunicación modernos que genera efectos memoria limitando la capacidad de transmitir señales de gran ancho de banda. El hecho de poder predecir la movilidad electrónica y la dispersión frecuencial ayudan al diseñador de circuitos a mejorar su calidad y tiempo de diseño. Además, permite a la industria de fabricación de componentes de RF ahorrar costos de producción pues esta técnica permite predecir el comportamiento de los circuitos antes de implementarlos. La metodología para la obtención del modelo compacto ha sido validada a través de la implementación de un amplificador de potencia en tecnología LDMOS usando la técnica propuesta. El modelo propuesto es abierto puesto que la nueva técnica propuesta se puede implementar en cualquiera de los modelos convencionales usados actualmente en el ámbito industrial y académico.

Nonlinear Analysis of High-Frequency FETs by a Hybrid Backward/Forward—FDTD Method

A hybrid backward/forward finite-difference time-domain (FDTD) method is suggested for efficient analysis of field-effect transistors (FETs) in the nonlinear regime. The distributed model is exploited wherein the FET is considered as a nonlinear active multiconductor transmission line. The Curtice cubic model is used to investigate the nonlinearity. Results are compared to the leap-frog (LF) FDTD. It is observed that stability of the method is not restricted to the Courant–Friedrichs–Lewy condition. The time gain of eight is achieved compared to the LF-FDTD with tolerable accuracy. The presented method is accurate enough with the week nonlinearity assumption.

Synthetic molecules for disruption of the MYC protein-protein interface

MYC is a key transcriptional regulator involved in cellular proliferation and has established roles in transcriptional elongation and initiation, microRNA regulation, apoptosis, and pluripotency. Despite this prevalence, functional chemical probes of MYC function at the protein level have been limited. Previously, we discovered 5a, that binds to MYC with potency and specificity, downregulates the transcriptional activities of MYC and shows efficacy in vivo. However, this scaffold posed intrinsic pharmacokinetic liabilities, namely, poor solubility that precluded biophysical interrogation. Here, we developed a screening platform based on field-effect transistor analysis (Bio-FET), surface plasmon resonance (SPR), and a microtumor formation assay to analyze a series of new compounds aimed at improving these properties. This blind SAR campaign has produced a new lead compound of significantly increased in vivo stability and solubility for a 40-fold increase in exposure. This probe represents a significant advancement that will not only enable biophysical characterization of this interaction and further SAR, but also contribute to advances in understanding of MYC biology.

Time domain analysis of field effect transistors using unconditionally stable finite difference method

In this study, an unconditionally stable finite difference time domain algorithm for time domain analysis of the active multiconductor transmission lines is presented. The results of the proposed algorithm are compared with the results of the conventional algorithm. While the results of the proposed algorithm have a very good accuracy, the CPU time of the proposed algorithm is less than (about 90%) that of the conventional one. The amplification matrixes of the proposed and conventional algorithms are extracted and numerical stability of them are investigated. The spectral radius of the presented algorithm is smaller than one for any temporal step sizes and the proposed algorithm is unconditionally stable.

Controlled doping of silicon nanocrystals investigated by solution-processed field effect transistors.

The doping of semiconductor nanocrystals (NCs), which is vital for the optimization of NC-based devices, remains a significant challenge. While gas-phase plasma approaches have been successful in incorporating dopant atoms into NCs, little is known about their electronic activation. Here, we investigate the electronic properties of doped silicon NC thin films cast from solution by field effect transistor analysis. We find that, analogous to bulk silicon, boron and phosphorus electronically dope Si NC thin films; however, the dopant activation efficiency is only ∼10(-2)-10(-4). We also show that surface doping of Si NCs is an effective way to alter the carrier concentrations in Si NC films.

Analysis of field effect transistors with arbitrary change distribution : R. R. Bockemuehl, Proc. I.E.E.E., ED-10, No. 1, p. 31 (1963)

Analysis of field effect transistors with arbitrary change distribution : R. R. Bockemuehl, Proc. I.E.E.E., ED-10, No. 1, p. 31 (1963)

Analysis of field effect transistors with arbitrary charge distribution

Solutions of field effect equations in which carrier density and space-charge distributions are considered in general form show that the LF terminal characteristics are not strongly dependent on the shape of the distribution curves. General expressions for mutual transconductance, output conductance, junction capacitance and current amplification are derived as functions of the depletion layer thickness at the device boundaries. These expressions are not explicitly dependent on charge distribution. Relationships between the small-signal and dc terminal characteristics depend on the shape of the charge distribution curves but cannot be varied by more than a factor of two. The shape of the device is shown to have secondary importance.