Electrical performance of conducting polymer (SPAN) grown on GaAs with different substrate orientations

This article reports the effect of n-type GaAs substrate orientation, namely (100), (311)A and (311)B, on the electrical properties of sulfonated polyaniline (SPAN)/GaAs heterojunction devices. In addition, the inhomogeneity of the interface between various GaAs substrates and SPAN is investigated in terms of barrier height and ideality factor by performing I–V measurements at different temperatures (20–420K). The I–V results indicate that the value of the rectification ratio (IF/IR) at 0.5V is higher for SPAN/(311)B GaAs samples than for SPAN/(100) GaAs and SPAN/(311)A GaAs samples. Moreover, the barrier height decreases and the ideality factor increases with decreasing temperature for all three heterostructure devices. The high value of mean barrier ˚¯ b of SPAN/(311)B (calculated from the plots of ˚b0 as a function of 1/2kT) confirms that the GaAs substrate orientation results in an increase of barrier homogeneities. Furthermore,the C-V characteristics were obtained at room temperature. The C-V measurements showed that the carrier distributions at the interface and away from the interface in high index (311) GaAs orientations are more uniform and have better barrier homogeneity than those grown on the conventional (100) GaAs substrates

Effect of Co-60 gamma-ray irradiation on electrical properties of Ti/Au/GaAs1-xNx Schottky diodes

Current-voltage (I-V), capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G/ω-V-f) measurements at room temperature are used to study 50 kGy 60Co γ-ray electrical properties irradiation dependence of Ti/Au/GaAs1−xNx Schottky diodes with 0.2%; 0.4%; 0.8% and 1.2% nitrogen dilution. This γ-ray irradiation induces a permanent damage that has increased ideality factor and series resistance for all samples. It was accompanied by a decrease in Schottky barrier height with nitrogen content up to 0.4%N and remained constant thereafter. Radiation was also found to degrade the reverse leakage current. At high frequency (1 MHz), capacitance and conductance decreased after radiation due to a decrease in net doping concentration. Interface state density and series resistance were determined from C-V-f and G/ω-V-f characteristics using Hill-Coleman methods. Interface states density exponentially decreased with increasing frequency confirming the behavior of interface traps response to ac signal. Series resistance increases after irradiation is attributed to carrier's removal effect and mobility degradation. It has two peaks in the accumulation and inversion region for some diodes (0.4%N, 0.8%N). γ-ray irradiation produced traps levels and recombination centers that reduce relaxation time. An increase in %N content can impede irradiation damage with even some compensation when the percent of diluted nitrogen is high (1.2%N)

Room temperature synthesis of porous gold nanostructures by controlled transmetallation reaction via chicken egg shell membrane

The formation of porous gold nanostructures in aqueous medium at room temperature using transmetallation reaction (TM reaction) that involves sacrificial silver nanoparticles and Au3+ ions (HAuCl4) controlled using a naturally available chicken egg shell membrane is reported in this article. The formation of porous gold nanostructures via TM reaction is inferred from UV-Vis absorption spectra. Crystallinity is confirmed by X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns. Porous gold tube like structures seen in the Field Emission Scanning Electron Microscopic (FESEM) images was confirmed by the Transmission Electron Microscopic (TEM) images. Energy dispersive spectroscopy (EDS) confirmed the presence of only gold in the final product. The porous gold nano structures could show fluorescence in Yeast cells, but the cell intake was limited. Glucose functionalized porous gold nanostructures could enter Yeast cells showing fluorescence, but the cells got killed. The synthesized porous nanostructures tagged with the cell permeant dye acridine orange (AO) was found to increase the fluorescence substantially in cell staining, compared to bare AO and AO tagged solid AuNPs. Present work illustrates the potential use of porous gold nanostructures in bio-imaging. (C) 2017 Elsevier B.V. All rights reserved

In-Situ X-Rays Diffraction and Multiscale Modeling of Shape Memory Alloys

International audienceIncreasing use of Shape Memory Alloys (SMA) for complex applications requires a robust modeling of phenomena governing their behavior. The development of micro-macro multiaxial model is relevant. Such approach relies the definition of transition scale rules, depending on the microstructure, and a description of the behavior of constituents. On the other hand, it requires experiments for identification of parameters such as enthalpies or kinetic constants and validation of the model. In this paper, in situ X-Ray Diffraction (XRD) measurements are performed during tensile tests and heating-cooling cycles. XRD permits monitoring of the average volume fraction of phases in presence. Results will be used for the validation of a multiscale and multiphased model

Ricinus communis pericarp activated carbon as an adsorbent for the removal of Pb(II) from aqueous solution and industrial wastewater

Environment Protection Engineering36183-94EPEN

Role of electron and phonon temperatures in the helicity-independent all-optical switching of GdFeCo

Ultrafast optical heating of the electrons in ferrimagnetic metals can result in all-optical switching (AOS) of the magnetization. Here we report quantitative measurements of the temperature rise of GdFeCo thin films during helicity-independent AOS. Critical switching fluences are obtained as a function of the initial temperature of the sample and for laser pulse durations from 55 fs to 15 ps. We conclude that nonequilibrium phenomena are necessary for helicity-independent AOS, although the peak electron temperature does not play a critical role. Pump-probe time-resolved experiments show that the switching time increases as the pulse duration increases, with 10 ps pulses resulting in switching times of ∼13 ps. These results raise new questions about the fundamental mechanism of helicity-independent AOS