Shrinking limits of silicon MOSFET's: Numerical study of 10-nm-scale devices

We have performed numerical modeling of dual-gate ballistic n-MOSFET's with channel length of the order of 10 nm, including the effects of quantum tunneling along the channel and through the gate oxide. Our analysis includes a self-consistent solution of the full (two-dimensional) electrostatic problem, with account of electric field penetration into the heavily-doped electrodes. The results show that transistors with channel length as small as 8 nm can exhibit either a transconductance up to 4,000 mS/mm or gate modulation of current by more than 8 orders of magnitude, depending on the gate oxide thickness. These characteristics make the devices satisfactory for logic and memory applications, respectively, though their gate threshold voltage is rather sensitive to nanometer-scale variations in the channel length.Comment: 8 pages, 10 figures. Submitted to Special Issue of Superlattices and Microstructures: Third NASA Workshop on Device Modeling, August 199

Direct tunneling through high-κ\kappa amorphous HfO2_2: effects of chemical modification

We report first principles modeling of quantum tunneling through amorphous HfO$_2$ dielectric layer of metal-oxide-semiconductor (MOS) nanostructures in the form of n-Si/HfO$_2$/Al. In particular we predict that chemically modifying the amorphous HfO$_2$ barrier by doping N and Al atoms in the middle region - far from the two interfaces of the MOS structure, can reduce the gate-to-channel tunnel leakage by more than one order of magnitude. Several other types of modification are found to enhance tunneling or induce substantial band bending in the Si, both are not desired from leakage point of view. By analyzing transmission coefficients and projected density of states, the microscopic physics of electron traversing the tunnel barrier with or without impurity atoms in the high-$\kappa$ dielectric is revealed.Comment: 5 pages, 5 figure

Antihistaminic activity of Ricinus communis roots using clonidine induced catalepsy in mice

Clonidine, an α2 adrenoreceptor agonist, induces dose dependent catalepsy in mice, which releases histamine from mast cells which is responsible for different asthmatic conditions. Ricinus communis Linn (Euphorbiaceae) is a medicinal plant; root is sweetish and has been used traditionally in the treatment of inflammation, pain fever, asthma, bronchititis and leprosy. In present study ethanol extract of R. communis roots (ERCR) at doses 100, 125 and 150 mg/kg intraperitoneally was evaluated for antihistaminic activity using clonidine induced catalepsy in mice. Finding of investigation showed that chlorpheniramine maleate and ERCR inhibit clonidine induced catalepsy significantly P < 0.001 when compare to control group. Present study concludes that ERCR possesses antihistaminic activity.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Computational Study of Tunneling Transistor Based on Graphene Nanoribbon

Tunneling field-effect transistors (FETs) have been intensely explored recently due to its potential to address power concerns in nanoelectronics. The recently discovered graphene nanoribbon (GNR) is ideal for tunneling FETs due to its symmetric bandstructure, light effective mass, and monolayer-thin body. In this work, we examine the device physics of p-i-n GNR tunneling FETs using atomistic quantum transport simulations. The important role of the edge bond relaxation in the device characteristics is identified. The device, however, has ambipolar I-V characteristics, which are not preferred for digital electronics applications. We suggest that using either an asymmetric source-drain doping or a properly designed gate underlap can effectively suppress the ambipolar I-V. A subthreshold slope of 14mV/dec and a significantly improved on-off ratio can be obtained by the p-i-n GNR tunneling FETs

A Three-Dimensional Quantum Simulation of Silicon Nanowire Transistors with the Effective-Mass Approximation

The silicon nanowire transistor (SNWT) is a promising device structure for future integrated circuits, and simulations will be important for understanding its device physics and assessing its ultimate performance limits. In this work, we present a three-dimensional quantum mechanical simulation approach to treat various SNWTs within the effective-mass approximation. We begin by assuming ballistic transport, which gives the upper performance limit of the devices. The use of a mode space approach (either coupled or uncoupled) produces high computational efficiency that makes our 3D quantum simulator practical for extensive device simulation and design. Scattering in SNWTs is then treated by a simple model that uses so-called Buttiker probes, which was previously used in metal-oxide-semiconductor field effect transistor (MOSFET) simulations. Using this simple approach, the effects of scattering on both internal device characteristics and terminal currents can be examined, which enables our simulator to be used for the exploration of realistic performance limits of SNWTs.Comment: 38 pages, 11 figures, submitted to Journal of Applied Physic

Digital power and performance analysis of inkjet printed ring oscillators based on electrolyte-gated oxide electronics

Printed electronic components offer certain technological advantages over their silicon based counterparts, like mechanical flexibility, low process temperatures, maskless and additive manufacturing possibilities. However, to be compatible to the fields of smart sensors, Internet of Things, and wearables, it is essential that devices operate at small supply voltages. In printed electronics, mostly silicon dioxide or organic dielectrics with low dielectric constants have been used as gate isolators, which in turn have resulted in high power transistors operable only at tens of volts. Here, we present inkjet printed circuits which are able to operate at supply voltages as low as <= 2 V. Our transistor technology is based on lithographically patterned drive electrodes, the dimensions of which are carefully kept well within the printing resolutions; the oxide semiconductor, the electrolytic insulator and the top-gate electrodes have been inkjet printed. Our inverters show a gain of similar to 4 and 2.3 ms propagation delay time at 1 V supply voltage. Subsequently built 3-stage ring oscillators start to oscillate at a supply voltage of only 0.6 V with a frequency of similar to 255 Hz and can reach frequencies up to similar to 350 Hz at 2 V supply voltage. Furthermore, we have introduced a systematic methodology for characterizing ring oscillators in the printed electronics domain, which has been largely missing. Benefiting from this procedure, we are now able to predict the switching capacitance and driver capability at each stage, as well as the power consumption of our inkjet printed ring oscillators. These achievements will be essential for analyzing the performance and power characteristics of future inkjet printed digital circuits

Switching Mechanism in Single-Layer Molybdenum Disulfide Transistors: an Insight into Current Flow across Schottky Barriers

In this article, we study the properties of metal contacts to single-layer molybdenum disulfide (MoS2) crystals, revealing the nature of switching mechanism in MoS2 transistors. On investigating transistor behavior as contact length changes, we find that the contact resistivity for metal/MoS2 junctions is defined by contact area instead of contact width. The minimum gate dependent transfer length is ~0.63 {\mu}m in the on-state for metal (Ti) contacted single-layer MoS2. These results reveal that MoS2 transistors are Schottky barrier transistors, where the on/off states are switched by the tuning the Schottky barriers at contacts. The effective barrier heights for source and drain barriers are primarily controlled by gate and drain biases, respectively. We discuss the drain induced barrier narrowing effect for short channel devices, which may reduce the influence of large contact resistance for MoS2 Schottky barrier transistors at the channel length scaling limit.Comment: ACS Nano, ASAP (2013

ROCSAT-1 telecommunication experiments

This paper addresses a telecommunication payload project approved by the R.O.C. NSPO's ROCSAT-1 space program. This project will enable several innovative experiments via the low-earth-orbit satellite ROCSAT-1, including multipath fading channel characterization, ionospheric scintillation measurement, real-time voice communications, and CDMA data communications. A unified L/S-band transponder payload is proposed for conducting these experiments in an efficient way. The results of these experiments would provide the evolving mobile communication communities with fruitful information