320 research outputs found
Annealing-Induced Modifications in Physicochemical and Optoelectronic Properties of Ag-Doped Nanostructured CdS Thin Films
The Ag-doped nanostructured CdS thin films are grown by simple, cost effective chemical ion exchange technique at room temperature on ITO-coated glass substrate. These as grown thin films are annealed at 100, 200, 300, and 400°C in air atmosphere for 1 hour. To study the effect of annealing on physicochemical and optoelectronic properties, these as grown and annealed thin films are characterized for structural, compositional, morphological, optical, and electrical properties. X-ray diffraction (XRD) pattern reveals polycrystalline nature of these thin films with increase in crystallite size from 6.4 to 11.2 nm, from XRD the direct identification of Ag doping in CdS thin films cannot be judged, while shift in characteristics peak position of CdS is observed. The Raman spectrum represents increase in full width at half maxima and intensity of characteristic peak, confirming the material modification upon annealing treatment. Presence of Cd, Ag, and S in energy dispersive X-ray analysis spectra (EDAX) confirms expected elemental composition in thin films. Scanning electron microscopy (SEM) images represent grain growth and agglomeration upon annealing. Red shift in optical absorbance strength and energy band gap values from 2.28 to 2.14 eV is obtained. I-V response obtained from as grown and annealed thin films shows an enhancement in photosensitivity from 72% to 96% upon illumination to 100 mW/cm2 light source
Direct tunneling through high- amorphous HfO: effects of chemical modification
We report first principles modeling of quantum tunneling through amorphous
HfO dielectric layer of metal-oxide-semiconductor (MOS) nanostructures in
the form of n-Si/HfO/Al. In particular we predict that chemically modifying
the amorphous HfO 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- dielectric is revealed.Comment: 5 pages, 5 figure
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
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
MENUMBUHKAN KESADARAN DAN KOMPETENSI INTERKULTURAL DALAM KELOMPOK MASYARAKAT YANG BERAGAM DI KABUPATEN SIKKA MELALUI PROYEK INTERKULTURAL
Penelitian ini bertujuan untuk (1) memahami interkulturalitas sebagai salah satu cara mengelola keberagaman di tengah masyarakat dan (2) mengembangkan kesadaran serta kompetensi interkultural di tengah masyarakat yang plural di kabupaten Sikka melalui proyek interkultural yang terencana, sistematis, dan terjadwal. Metode yang digunakan dalam penelitian ini ialah deskriptif kualitatif. Subjek dalam penelitian ini mencakup lima kelompok sasar. Wujud data dalam penelitian ini berupa sumber data primer dan sekunder dari hasil wawancara, observasi partisipatoris, pembicaraan tidak resmi, dan focus group discussion dengan kelompok sasar. Selain itu, peneliti juga memperoleh data dari sejumlah referensi yang berhubungan dengan tema ini. Penelitian ini menemukan bahwa alih-alih dijadikan sebagai sumber konflik dalam kehidupan bersama, perbedaan dan keberagaman perlu diatur dan dikelola dengan baik sebagai potensi kultural dalam membangun kehidupan bersama yang damai, ramah, harmonis dan interaktif. Pendekatan interkultural menjadi salah satu pendekatan yang memprioritaskan semangat saling menghormati, membangun kesatuan dalam keragaman, membina interaksi, dialog timbal balik, menghidupkan semangat persaudaraan dan saling belajar lintas batas. Kesadaran demikian perlu dibina melalui proyek interkultural yang dirancang secara terencana, sadar, partisipatif, sistematis dan diterapkan secara tetap dan berkesinambungan demi mencapai kebaikan bersama
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
A review of selected topics in physics based modeling for tunnel field-effect transistors
The research field on tunnel-FETs (TFETs) has been rapidly developing in the last ten years, driven by the quest for a new electronic switch operating at a supply voltage well below 1 V and thus delivering substantial improvements in the energy efficiency of integrated circuits. This paper reviews several aspects related to physics based modeling in TFETs, and shows how the description of these transistors implies a remarkable innovation and poses new challenges compared to conventional MOSFETs. A hierarchy of numerical models exist for TFETs covering a wide range of predictive capabilities and computational complexities. We start by reviewing seminal contributions on direct and indirect band-to-band tunneling (BTBT) modeling in semiconductors, from which most TCAD models have been actually derived. Then we move to the features and limitations of TCAD models themselves and to the discussion of what we define non-self-consistent quantum models, where BTBT is computed with rigorous quantum-mechanical models starting from frozen potential profiles and closed-boundary Schr\uf6dinger equation problems. We will then address models that solve the open-boundary Schr\uf6dinger equation problem, based either on the non-equilibrium Green's function NEGF or on the quantum-transmitting-boundary formalism, and show how the computational burden of these models may vary in a wide range depending on the Hamiltonian employed in the calculations. A specific section is devoted to TFETs based on 2D crystals and van der Waals hetero-structures. The main goal of this paper is to provide the reader with an introduction to the most important physics based models for TFETs, and with a possible guidance to the wide and rapidly developing literature in this exciting research field
Gastrointestinal microbiota composition predicts peripheral inflammatory state during treatment of human tuberculosis
The composition of the gastrointestinal microbiota influences systemic immune responses, but how this affects infectious disease pathogenesis and antibiotic therapy outcome is poorly understood. This question is rarely examined in humans due to the difficulty in dissociating the immunologic effects of antibiotic-induced pathogen clearance and microbiome alteration. Here, we analyze data from two longitudinal studies of tuberculosis (TB) therapy (35 and 20 individuals) and a cross sectional study from 55 healthy controls, in which we collected fecal samples (for microbiome analysis), sputum (for determination of Mycobacterium tuberculosis (Mtb) bacterial load), and peripheral blood (for transcriptomic analysis). We decouple microbiome effects from pathogen sterilization by comparing standard TB therapy with an experimental TB treatment that did not reduce Mtb bacterial load. Random forest regression to the microbiome-transcriptome-sputum data from the two longitudinal datasets reveals that renormalization of the TB inflammatory state is associated with Mtb pathogen clearance, increased abundance of Clusters IV and XIVa Clostridia, and decreased abundance of Bacilli and Proteobacteria. We find similar associations when applying machine learning to peripheral gene expression and microbiota profiling in the independent cohort of healthy individuals. Our findings indicate that antibiotic-induced reduction in pathogen burden and changes in the microbiome are independently associated with treatment-induced changes of the inflammatory response of active TB, and the response to antibiotic therapy may be a combined effect of pathogen killing and microbiome driven immunomodulation
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