(Au, Ag)/Al0.08In0.08Ga0.84N/ (Au, Ag) Metal-semiconductor-metal (MSM) Photodetectors

Metal-semiconductor-metal (MSM) photodetectors (PDs) based on gold and silver (Au, Ag)/Al0.08In0.08Ga0.84N (commercial sample)/ (Au, Ag) have been fabricated and characterized. The effect of annealing temperature of As deposit, 400, 500, and 600 0C for 30 min on the topography and electrical properties of Au contact on Al0.08In0.08Ga0.84N thin film have been characterized and optimized using Current-Voltage (I-V) characteristic. Schottky barrier height (SBH) and ideality factor (n) of Au/ Al0.08In0.08Ga0.84N interface were 1.223 eV and 1.773 at 50 0C annealing temperature for 30 min respectively, and it is found that contact has a high-quality surface. Also, with the same procedure, the effect of annealing time of 15, 30, 45 minutes, and 1 hour have been studied and optimized. The results revealed that the best annealing time is 30 min which has the highest SBH. Au contact compared with Ag contact used to first time as best our knowledge with the optimal condition to select the best metal for MSM photodetectors (PDs). The ideal characterization of Au, Ag/AlInGaN/Au, Ag MSMPDs on Si substrate depend on responsivities of 0.201 and 0.153 A W-1, quantum efficiencies of 71% and 57%, and NEPs of 3.55×10-4 and 1.45×10-3W-1, respectively have been also studied compared. The height SBH and QE for the samples grown on Si was at Au contact which proposed to use in such optoelectronic devices.

A Novel Characterization and Performance Measurement of Memristor Devices for Synaptic Emulators in Advanced Neuro-Computing

The advanced neuro-computing field requires new memristor devices with great potential as synaptic emulators between pre- and postsynaptic neurons. This paper presents memristor devices with TiO2 Nanoparticles (NPs)/Ag(Silver) and Titanium Dioxide (TiO2) Nanoparticles (NPs)/Au(Gold) electrodes for synaptic emulators in an advanced neurocomputing application. A comparative study between Ag(Silver)- and Au(Gold)-based memristor devices is presented where the Ag electrode provides the improved performance, as compared to the Au electrode. Device characterization is observed by the Scanning Electron Microscope (SEM) image, which displays the grown electrode, while the morphology of nanoparticles (NPs) is verified by Atomic Force Microscopy (AFM). The resistive switching (RS) phenomena observed in Ag/TiO2 and Au/TiO2 shows the sweeping mechanism for low resistance and high resistance states. The resistive switching time of Au/TiO2 NPs and Ag/TiO2 NPs is calculated, while the theoretical validation of the memory window demonstrates memristor behavior as a synaptic emulator. Measurement of the capacitor–voltage curve shows that the memristor with Ag contact is a good candidate for charge storage as compared to Au. The classification of 3 × 3 pixel black/white image is demonstrated by the 3 × 3 cross bar memristor with pre- and post-neuron system. The proposed memristor devices with the Ag electrode demonstrate the adequate performance compared to the Au electrode, and may present noteworthy advantages in the field of neuromorphic computing.

Investigation of the Screen-printable Ag/Cu Contact for Si Solar Cells Using Microstructural, Optical and Electrical Analyses

ABSTRACTIn a bid to further reduce the cost of the front Ag contact metallization in Si solar cells, Cu is the potential alternative to replace the Ag in the Ag paste. However, this requires an understanding of the contact mechanism of screen-printable Ag/Cu paste in Si solar cell through rapid thermal process. The pastes with different weight percent of Cu (0 wt%, 25 wt% and 50 wt%) were used and the Voc of the cells was reduced with the increasing weight percent of Cu. This is because the presence of Cu in the paste changed the microstructure of the Ag/Cu/Si contact through Cu doping of the glass frits and hence increasing the Tg of the glass. The increased Tg of the glass impeded the uniform spreading of the molten glass and resulted in poor wetting and etching of the SiNx, which impacted the contact as evident in ideality factor of less than unity. This also led to the formation of agglomerated Ag crystallites with features of 700 nm in length and 200 nm in depth, which is close to the p-n junction, of which depth is ∼300 nm. However, the interface glass layer acted as an effective diffusion barrier layer to prevent Cu atoms from diffusing into the Si emitter, which is quite remarkable for Cu not to diffuse into silicon at high temperature. Further investigation of the Ag/Cu contacts with the conductive AFM in conjunction with the SEM and STEM analyses revealed that the growth of Ag crystallites in the Si emitter is responsible for carrier conduction the gridlines as with the pure Ag paste.

Thermoelectric Properties of Thin Films of Germanium-Gold Alloy Obtained by Magnetron Sputtering

In this paper, the electric and thermoelectric properties of thin films of germanium–gold alloy (Ge–Au) are discussed in terms of choosing the optimal deposition process and post-processing conditions to obtain Ge–Au layers with the best thermoelectric parameters. Thin films were fabricated by magnetron sputtering using the Ge–Au alloy target onto glass substrates at two various conditions; during one of the sputtering processes, the external substrate bias voltage (Ub = −150 V) was used. After deposition thin films were annealed in the atmosphere of N2 at various temperatures (473, 523 and 573 K) to investigate the influence of annealing temperature on the electric and thermoelectric properties of films. Afterwards, the thermocouples were created by deposition of the NiCrSi/Ag contact pads onto Ge–Au films. In this work, particular attention has been paid to thermoelectric properties of fabricated thin films—the thermoelectric voltage, Seebeck coefficient, power factor PF and dimensionless figure of merit ZT were determined.

Vamp-7–dependent secretion at the immune synapse regulates antigen extraction and presentation in B-lymphocytes

Recognition of surface-tethered antigens (Ags) by B-cells leads to the formation of an immune synapse that promotes Ag uptake for presentation onto MHC-II molecules. Extraction of immobilized Ags at the immune synapse of B-cells relies on the local secretion of lysosomes, which are recruited to the Ag contact site by polarization of their microtubule network. Although conserved polarity proteins have been implicated in coordinating cytoskeleton remodeling with lysosome trafficking, the cellular machinery associated with lysosomal vesicles that regulates their docking and secretion at the synaptic interface has not been defined. Here we show that the v-SNARE protein Vamp-7 is associated with Lamp-1+ lysosomal vesicles, which are recruited and docked at the center of the immune synapse of B-cells. A decrease in Vamp-7 expression does not alter lysosome transport to the synaptic interface but impairs their local secretion, a defect that compromises the ability of B-cells to extract, process, and present immobilized Ag. Thus our results reveal that B-cells rely on the SNARE protein Vamp-7 to promote the local exocytosis of lysosomes at the immune synapse, which is required for efficient Ag extraction and presentation.

Counter-anion role in the formation of two supramolecular complexes: [Ag2(DPP)2](ClO4)2·CH3CN and [Ag2(DPP)2(NO3)2] {DPP isN-[(diphenylphosphanyl)methyl]pyridin-4-amine}

The title compounds, bis{μ-N-[(diphenylphosphanyl)methyl]pyridin-4-amine-κ2N1:P}disilver bis(perchlorate) acetonitrile monosolvate, [Ag2(C18H17N2P)2](ClO4)2·CH3CN, (1), and bis{μ-N-[(diphenylphosphanyl)methyl]pyridin-4-amine-κ2N1:P}bis[(nitrato-κ2O,O)silver], [Ag2(C18H17N2P)2(NO3)2], (2), each contain disilver macrocyclic [Ag2(C18H17N2P)2]2+cations lying about inversion centres. The cations are constructed by twoN-[(diphenylphosphanyl)methyl]pyridin-4-amine (DPP) ligands linking two Ag+cations in a head-to-tail fashion. In (1), the unique Ag+cation has a near-linear coordination geometry consisting of one pyridine N atom and one P atom from two different DPP ligands. Two ClO4−anions doubly bridge two metallomacrocycles through Ag...O and N—H...O weak interactions to form a chain extending in thecdirection. The half-occupancy acetonitrile molecule lies with its methyl C atom on a twofold axis and makes a weak N...Ag contact. In (2), there are two independent [Ag(C18H17N2P)]+cations. The nitrate anions weakly chelate to each Ag+cation, leading to each Ag+cation having a distorted tetrahedral coordination geometry consisting of one pyridine N atom and one P atom from two different DPP ligands, and two chelating nitrate O atoms. Each dinuclear [Ag2(C18H17N2P)2(NO3)2] molecule acts as a four-node to bridge four adjacent equivalent molecules through N—H...O interactions, forming a two-dimensional sheet parallel to thebcplane. Each sheet contains dinuclear molecules involving just Ag1 or Ag2 and these two types of sheet are stacked in an alternating fashion. The sheets containing Ag1 all lie nearx= {1 \over 2}, {3 \over 2}, {5 \over 2}etc, while those containing Ag2 all lie nearx= 0, 1, 2etc. Thus, the two independent sheets are arranged in an alternating sequence atx= 0, {1 \over 2}, 1, {3 \over 2}etc. These two different supramolecular structures result from the different geometric conformations of the templating anions which direct the self-assembly of the cations and anions.