Inclusion of body doping in compact models for fully-depleted common double gate MOSFET adapted to gate-oxide thickness asymmetry

Since it is difficult to find the analytical solution of the governing Poisson equation for double gate MOSFETs with the body doping term included, the majority of the compact models are developed for undoped-body devices for which the analytical solution is available. Proposed is a simple technique to included a body doping term in such surface potential based common double gate MOSFET models also by taking into account any differences between the gate oxide thickness. The proposed technique is validated against TCAD simulation and found to be accurate as long as the channel is fully depleted.

Thermal diffusivity measurements on ternary Ge-Te-Tl glasses using Photo-thermal Deflection method: Effect of thallium addition

Photo-thermal Deflection (PTD) technique is used to investigate the thermal diffusivity (alpha) of Ge17Te83 - xTlx (0 <= x <= 13) glasses as a function of composition. The thermal diffusivity of these glasses is found to lie in the range 0.020 to 0.048 cm(2)/s, which is consistent with the memory type of electrical switching exhibited by these samples. Further, it is found that alpha shows an initial increase with Tl addition, followed by a decrease. The observed composition dependence of thermal diffusivity has been understood on the basis that the thallium atoms are incorporated as a covalent species for lower values of x, increasing the network rigidity; however, they enter as ionic species for higher x values, fragmenting the network. The initial increase in a is due to the increasing network rigidity and the subsequent decrease is because of the fragmentation of the network. Also, there is a strong correlation between the composition dependence of switching voltages observed earlier and the variation with composition of electrical resistivity and thermal diffusivity of Ge17Te83 - xTlx glasses obtained in the present study. (C) 2012 Elsevier B.V. All rights reserved.

Threshold voltage modeling under size quantization for ultra-thin silicon double-gate metal-oxide-semiconductor field-effect transistor

We report on the threshold voltage modeling of ultra-thin (1 nm-5 nm) silicon body double-gate (DG) MOSFETs using self-consistent Poisson-Schrodinger solver (SCHRED). We define the threshold voltage (V th) of symmetric DG MOSFETs as the gate voltage at which the center potential (Φ c) saturates to Φ c (s a t), and analyze the effects of oxide thickness (t ox) and substrate doping (N A) variations on V th. The validity of this definition is demonstrated by comparing the results with the charge transition (from weak to strong inversion) based model using SCHRED simulations. In addition, it is also shown that the proposed V t h definition, electrically corresponds to a condition where the inversion layer capacitance (C i n v) is equal to the oxide capacitance (C o x) across a wide-range of substrate doping densities. A capacitance based analytical model based on the criteria C i n v C o x is proposed to compute Φ c (s a t), while accounting for band-gap widening. This is validated through comparisons with the Poisson-Schrodinger solution. Further, we show that at the threshold voltage condition, the electron distribution (n(x)) along the depth (x) of the silicon film makes a transition from a strong single peak at the center of the silicon film to the onset of a symmetric double-peak away from the center of the silicon film. © 2012 American Institute of Physics.

Zinc Oxide Modified Au Electrode as Sensor for an Efficient Detection of Hydrazine

ZnO nanoparticles (ZnO NPs) prepared by microwave heating technique are used to modify a gold electrode (ZnO/Au) for the hydrazine detection study. The synthesized product is well characterized by various techniques. Detailed electrochemical investigation of the oxidation of hydrazine on the ZnO/Au electrode in 0.02 M phosphate buffer solution (PBS) of pH 7.4 was carried out. A very low detection limit of 66 nM (S/N=4) and a wide linearity in current for a concentration range from 66.0X10-3 to 415 mu M was achieved by amperometry. The electrode was found to be stable for over a month when preserved in PBS.

Covalently Linked, Water-Dispersible, Cyciodextrin: Reduced-Graphene Oxide Sheets

Reduced-graphene oxide (rGO) sheets have been functionalized by covalently linking beta-cyclodextrin (beta CD) cavities to the sheets via an amide linkage. The functionalized beta-CD:rGO sheets, in contrast to rGO, are dispersible over a wide range of pH values (2-13). Zeta potential measurements indicate that there is more than one factor responsible for the dispersibility. We show here that planar aromatic molecules adsorbed on the rGO sheet as well as nonplanar molecules included in the tethered beta-CD cavities have their fluorescence effectively quenched by the beta-CD:rGO sheets. The beta-CD:rGO sheets combine the hydrophobicity associated with rGO along with the hydrophobicity of the cyclodextrin cavities in a single water-dispersible material.

Effect of doping concentration on the structural and optical properties of pure and tin doped zinc oxide thin films by nebulizer spray pyrolysis (NSP) technique

Pure and tin doped zinc oxide (Sn:ZnO) thin films were prepared for the first time by NSP technique using aqueous solutions of zinc acetate dehydrate, tin (IV) chloride fendahydrate and methanol. X-ray diffraction patterns confirm that the films are polycrystalline in nature exhibiting hexagonal wurtzite type, with (0 0 2) as preferred orientation. The structural parameters such as lattice constant ('a' and `c'), crystallite size, dislocation density, micro strain, stress and texture coefficient were calculated from X-ray diffraction studies. Surface morphology was found to be modified with increasing Sn doping concentration. The ZnO films have high transmittance 85% in the visible region, and the transmittance is found to be decreased with the increase of Sn doping concentration. The corresponding optical band gap decreases from 3.25 to 3.08 eV. Room temperature photoluminescence reveals the sharp emission of strong UV peak at 400 nm (3.10 eV) and a strong sharp green luminescence at 528 nm (2.34 eV) in the Sn doped ZnO films. The electrical resistivity is found to be 10(6) Omega-cm at higher temperature and 10(5) Omega-cm at lower temperature. (C) 2012 Elsevier Ltd. All rights reserved.

Synthesis of zinc oxide porous structures by anodization with water as an electrolyte

We report a simple, reliable and one-step method of synthesizing ZnO porous structures at room temperature by anodization of zinc (Zn) sheet with water as an electrolyte and graphite as a counter electrode. We observed that the de-ionized (DI) water used in the experiment is slightly acidic (pH=5.8), which is due to the dissolution of carbon dioxide from the atmosphere forming carbonic acid. Porous ZnO is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence (PL) studies. The current-transient measurement is carried out using a Gamry Instruments Reference 3000 and the thickness of the deposited films is measured using a Dektak surface profilometer. The PL, Raman and X-ray photoelectron spectroscopy are used to confirm the presence of ZnO phase. We have demonstrated that the hybrid structures of ZnO and poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) exhibit good rectifying characteristics. The evaluated barrier height and the ideality factor are 0.45 eV and 3.6, respectively.

Ex Situ X-ray Diffraction, X-ray Absorption Near Edge Structure, Electron Spin Resonance, and Transmission Electron Microscopy Study of the Hydrothermal Crystallization of Vanadium Oxide Nanotubes: An Insight into the Mechanism of Formation

The nucleation and growth of vanadium oxide nanotubes (VOx-NT) have been followed by a combination of numerous ex situ techniques. long the hydrothermal process. Intermediate solid phases extracted at different reaction times have been characterized by powder X-ray diffraction, scanning and transmission electron microscopy, electron spin resonance, and V-K edge :X-ray absorption near-edge structure spectroscopy. The supernatant vanadate solutions extracted during the hydrothermal treatment have been studied by liquid V-51 NMR and flame. spectroscopy. For short durations of the hydrothermal synthesis, the initial V2O5-surfactant intercalate. is progressively transformed into VOx-NT whose crystallization starts to be detected after a hydrothermal treatment of 24 h. Upon heating from 24 h to 7 days, VOx-NT are obtained in larger amount and with an improved crystallinity. The detection of soluble amines and cyclic metavanadate V4O12](4-) in the supernatant solution along the hydrothermal process suggests that VOx-NT result from a dissolution precipitation mechanism. Metavanadate species V4O12](4-) could behave as molecular precursors in the polymerization reactions leading to VOx-NT.

Manifestation of intermediate phase in mechanical properties: Nano-indentation studies on Ge-Te-Si bulk chalcogenide glasses

Nano-indentation studies have been undertaken on bulk Ge15Te85-xSix glasses (0 <= x <= 9), to estimate hardness, H and elastic modulus, E. It is found that E and H increase initially with the increase in the atomic percent of Si. Further, a plateau is seen in the composition dependence of E and H in the composition range 2 <= x <= 6. It is also seen that the addition of up to 2 at% Si increases the density rho of the glass considerably; however, further additions of Si lead to a near linear reduction in rho, in the range 2 <= x <= 6. Beyond x=6, rho increases again with Si content. The variation of molar volume V-m brings out a more fascinating picture. A plateau is seen in the intermediate phase suggesting that the molecular structure of the glasses is adapting to keep the count of constraints fixed in this particular phase. The observed variations in mechanical properties are associated with the Boolchand's intermediate phase in the present glassy system, in the composition range 2 <= x <= 6, suggested earlier from calorimetric and electrical switching studies. The present results reveal rather directly the existence of the intermediate phase in elastic and plastic properties of chalcogenide glasses. (C) 2012 Elsevier Ltd. All rights reserved.

Near-infrared light-responsive graphene oxide composite multilayer capsules: a novel route for remote controlled drug delivery

A novel and simple route for near-infrared (NIR)-light controlled release of drugs has been demonstrated using graphene oxide (GO) composite microcapsules based on the unique optical properties of GO. Upon NIR-laser irradiation, the microcapsules were ruptured in a point-wise fashion due to local heating which in turn triggers the light-controlled release of the encapsulated anticancer drug doxorubicin (Dox) from these capsules.

Synthesis, characterisation, and DC conductivity of polyaniline-lead oxide composites

The polyaniline-PbO composites of various mass fractions were prepared by in situ polymerisation. The prepared samples were characterised by FTIR, and the dominant peaks confirmed the formation of polyaniline-PbO composites. The SEM study shows a granular agglomerated morphology, and increases with an increase in the lead oxide mass % in polyaniline. Direct current (DC) conductivity (sigma (DC)) was studied as a function of temperature (T). From these studies, it was found that conductivity increased at higher temperatures due to the polarons hopping from one localised state to another. DSC studies reveal, the decrease in peak temperature from 273A degrees C (pure PANI) to 169.2A degrees C, 193.5A degrees C, 218.4A degrees C, 235.2A degrees C, and 224.2A degrees C, respectively for the various mass fractions (10 %, 30 %, 20 %, 40 %, and 50 %) of polyaniline-PbO composites.

Thermally reversing window in Ge15Te85-xInx glasses: Nanoindentation and micro-Raman studies

Nanoindentation studies on Ge15Te85-xInx glasses indicate that the hardness and elastic modulus of these glasses increase with indium concentration. While a pronounced plateau is seen in the elastic modulus in the composition range 3 <= x <= 7, the hardness exhibits a change in slope at compositions x = 3 and x = 7. Also, the density exhibits a broad maximum in this composition range. The observed changes in the mechanical properties and density are clearly associated with the thermally reversing window in Ge15Te85-xInx glasses in the composition range 3 <= x <= 7. In addition, a local minimum is seen in density and hardness around x = 9, the chemical threshold of the system. Further, micro-Raman studies reveal that as-quenched Ge15Te85-xInx samples exhibit two prominent peaks, at 123 cm(-1) and 155 cm(-1). In thermally annealed samples, the peaks at 120 cm(-1) and 140 cm(-1), which are due to crystalline Te, emerge as the strongest peaks. The Raman spectra of polished samples are similar to those of annealed samples, with strong peaks at 123 cm(-1) and 141 cm(-1). The spectra of lightly polished samples outside the thermally reversing window resemble those of thermally annealed samples; however, the spectra of glasses with compositions in the thermally reversing window resemble those of as-quenched samples. This observation confirms the earlier idea that compositions in the thermally reversing window are non-aging and are more stable. (C) 2012 Elsevier B.V. All rights reserved.

Electrical transport characteristics of ZnO-Bi2O3-B2O3 glasses

Optically clear glasses in the ZnO-Bi2O3-B2O3 (ZBBO) system were fabricated via the conventional melt-quenching technique. Dielectric constant and loss measurements carried out on ZBBO glasses unraveled nearly frequency (1 kHz-10 MHz)-independent dielectric characteristics associated with significantly low loss (D = 0.004). However, weak temperature response was found with temperature coefficient of dielectric constant 18 +/- 4 ppm A degrees C-1 in the 35-250 A degrees C temperature range. The conduction and relaxation phenomena were rationalized using universal AC conductivity power law and modulus formalism respectively. The activation energy for relaxation determined using imaginary parts of modulus peaks was 2.54 eV which was close to that of the DC conduction implying the involvement of similar energy barriers in both the processes. Stretched and power exponents were temperature dependent. The relaxation and conduction in these glasses were attributed to the hoping and migration of Bi3+ cations in their own and different local environment.

Electron field emission from reduced graphene oxide on polymer film

Field emission of reduced graphene oxide coated on polystyrene film is studied in both parallel and perpendicular configurations. Low turn-on field of 0.6 V/lm and high emission current density of 200 mA/cm(2) are observed in perpendicular configuration (along the cross section), whereas a turn-on field of 6 V/lm and current density of 20 mu A/cm(2) are obtained in parallel configuration (top surface). The emission characteristics follow Fowler-Nordheim (FN) tunneling and the values of enhancement factor estimated from FN plots are 5818 (perpendicular) and 741 (parallel). Furthermore, stability and repeatability of the field emission characteristics in perpendicular configuration are presented. (C) 2013 American Institute of Physics. http://dx.doi.org/10.1063/1.4788738]

Detection of glycated hemoglobin using 3-Aminophenylboronic acid modified graphene oxide

This paper presents the chemical synthesis of 3-Aminophenylboronic acid (APBA) modified graphene oxide (GO) and its application to the electrochemical detection of glycated hemoglobin (GHb). The compound (GO-APBA) was synthesized by forming an amide linkage between the amino group (-NH2) of APBA and the carboxylic group (-COOH) of GO. The compound was characterized using IR spectroscopy. Detection of GHb was carried out using Electrochemical Impedance Spectroscopic (EIS) measurements with GO-APBA modified glassy carbon electrode as the working electrode.