This paper tackles the issue of downscaling of an ohmic contact from the infinite approximation to nanometer dimensions. Using the finite-element simulation program, it is shown that small-size ohmic ...contacts on a wide-bandgap semiconductor exhibit nonlinear current-voltage dependence in case velocity saturation is introduced. Furthermore, the dependence becomes asymmetrical around zero bias. In addition, it is shown that in small-size contacts, a nonlocal tunneling is bound to occur even in pure ohmic contacts. This may explain the absence of linear I - V curves in the reported experiments with nanometer-scale contacts.
Bispecific antibody MEDI3902, targeting the Pseudomonas aeruginosa type 3 secretion system (PcrV) and Psl exopolysaccharide, is currently in phase 2b development for prevention of nosocomial ...pneumonia in patients undergoing mechanical ventilation. We surveyed a diverse collection of isolates to study MEDI3902 epitope conservation and protective activity.
P. aeruginosa clinical isolates (n = 913) were collected from diverse patients and geographic locations during 2003-2014. We conducted whole-genome sequencing; performed PcrV and Psl expression analyses via immunoblotting and enzyme-linked immunosorbent assay, respectively; performed crystallography to determine the MEDI3902 PcrV epitope, using anti-PcrV Fab and PcrV components (resolved at 2.8 Å); and evaluated MEDI3902 protective activity against select isolates in vitro and in vivo.
Intact psl operon and pcrV genes were present in 94% and 99% of isolates, respectively, and 99.9% of isolates contained at least one of the genetic elements. Anti-Psl binding was confirmed in tested isolates harboring a complete Psl operon or lacking nonessential psl genes. We identified 46 PcrV variant sequences, and MEDI3902-PcrV contact residues were preserved. MEDI3902 maintained potent in vivo activity against various strains, including strains expressing only a single target.
Psl and PcrV are highly prevalent in global clinical isolates, suggesting MEDI3902 can mediate broad coverage against P. aeruginosa.
Current simulation of symmetric contacts on CdTe Ruzin, A.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2011, Letnik:
658, Številka:
1
Journal Article
Recenzirano
This article presents the calculated current–voltage characteristics of symmetric Metal–Semiconductor–Metal configurations for Schottky, Ohmic, and injecting-Ohmic contacts on high resistivity CdTe. ...The results clearly demonstrate that in the wide band-gap, semi-insulating semiconductors, such as high resistivity CdTe, the linearity of the
I–
V curves cannot be considered a proof of the ohmicity of the contacts. It is shown that the linear
I–
V curves are expected for a wide range of contact barriers. Furthermore, the slope of these linear curves is governed by the barrier height, rather than the bulk doping concentration. Therefore the deduction of bulk's resistivity from the
I–
V curves may be false.
Effects of oxygen plasma treatment on Cd1−xZnxTe material and devices Brovko, A.; Amzallag, O.; Adelberg, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2021, Letnik:
1004
Journal Article
Recenzirano
Surface passivation in detectors is designed to improve the performance and stabilize the characteristics over time and ambient. In Cd1−xZnxTe radiation detectors, oxidation by plasma is a well-known ...passivation method, but its physics is not fully understood. This study focuses on the macroscopic and microscopic effects of plasma treatment. It is shown that plasma oxidation before contact deposition causes a considerable decrease in the device’s dark current and that this reduction is in a strong correlation with the lowering of the surface potential. X-ray photoelectron spectroscopy (XPS) measurements revealed a significant increase in TeO 2 fraction on the plasma-treated surface. The main conclusion of this study is that the plasma-related effects are not confined to the surface layer. Furthermore, the deep penetration of plasma treatment byproduct takes place over long time periods, which may lead to variations in device characteristics. The effects were corroborated by several characterization techniques. DC current–voltage measurements combined with layer-by-layer stripping indicate plasma signature deep into the bulk. Transient current technique (TCT) results demonstrate that the plasma treatment affects the electric field distribution millimeters into the bulk. Photo-induced current transient spectroscopy (PICTS) and thermoelectric emission spectroscopy (TEES) measurements reveal plasma-related traps in-depth of the CdZnTe crystals.
Grain boundaries (GBs) participate in the photovoltaic energy conversion process in polycrystalline solar cells as efficient photocurrent collectors and transporters, as shown by high‐ resolution ...characterization of CdTe GBs in CdTe/CdS cells (see Figure). This suggests that structural defects can be advantageous for device performance, if properly designed, even in devices whose operation is based on physics of ideal, perfect solids.
Objectives The purpose of this study was to characterize decreased susceptibility to tigecycline in clinical isolates of Escherichia coli obtained during Phase 3 clinical trials. Methods Gene ...expression was analysed by transcriptional profile analysis and RT-PCR. Transposon mutagenesis with IS903ϕkan was used for selection of transposon mutants. Transposon insertions were mapped by DNA sequencing and PCR analyses. The MICs were determined by broth microdilution. Results Both transcriptional profile analysis and Taqman RT-PCR demonstrated increased expression levels of MarA, a transcriptional activator, and AcrAB, an RND-type efflux pump, in the strains with elevated tigecycline MICs. Transposon mutagenesis generated nine mutants, the majority of which had either marA or acrB inactivated. Sequence analysis revealed a single nucleotide insertion in the open reading frame of the marR gene in less-susceptible strains of E. coli. Conclusions This study suggested that a loss of MarR functionality due to a frameshift mutation resulted in constitutive overproduction of MarA and AcrAB and, consequently, in decreased susceptibility to tigecycline in clinical isolates of E. coli.
The superior performance of certain polycrystalline (PX) solar cells compared to that of corresponding single‐crystal ones has been an enigma until recently. Conventional knowledge predicted that ...grain boundaries serve as traps and recombination centers for the photogenerated carriers, which should decrease cell performance. To understand if cell performance is limited by grain bulk, grain surface, and/or grain boundaries (GBs), we performed high‐resolution mapping of electronic properties of single GBs and grain surfaces in PX p‐CdTe/n‐CdS solar cells. Combining results from scanning electron and scanning probe microscopies, viz., capacitance, Kelvin probe, and conductive probe atomic force microscopies, and comparing images taken under varying conditions, allowed elimination of topography‐related artifacts and verification of the measured properties. Our experimental results led to several interesting conclusions: 1) current is depleted near GBs, while photocurrents are enhanced along the GB cores; 2) GB cores are inverted, which explains GB core conduction. Conclusions (1) and (2) imply that the regions around the GBs function as an extension of the carrier‐collection volume, i.e., they participate actively in the photovoltaic conversion process, while conclusion (2) implies minimal recombination at the GB cores; 3) the surface potential is diminished near the GBs; and 4) the photovoltaic and metallurgical junction in the n‐CdS/p‐CdTe devices coincide. These conclusions, taken together with gettering of defects and impurities from the bulk into the GBs, explain the good photovoltaic performance of these PX cells (at the expense of some voltage loss, as is indeed observed). We show that these CdTe GB features are induced by the CdCl2 heat treatment used to optimize these cells in the production process.
Polycrystallinity can be good for solar cells. Defects such as grain boundaries, which are thought to decrease performance of polycrystalline solar cells, can participate in, and help photovoltaic conversion, as we show for CdTe grain boundaries in polycrystalline thin film CdTe/CdS cells. The figure shows simultaneously collected topography and current maps of a CdTe surface.
Recent results from the RD-48 (ROSE) Collaboration Ruzin, A
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2000, Letnik:
447, Številka:
1
Journal Article
Recenzirano
The current status of the research carried out by the RD-48 (ROSE) Collaboration is presented. Results of macroscopic and microscopic experimental studies are described as well as the progress in ...modeling. Detectors with improved radiation hardness were achieved by oxygen enrichment of silicon. The oxygen concentration required to obtain the improvement is ∼10
17
cm
−3.
Simulation of compensated and overcompensated Cd1−xZnxTe Ruzin, A.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Letnik:
718
Journal Article
Recenzirano
Ohmic and Schottky contacts were simulated on Cd0.9Zn0.1Te compensated by deep traps under thermodynamic equilibrium conditions. It is demonstrated that addition of deep levels with specific electric ...properties can compensate and over-compensate the semiconductor. The pinning of the Fermi level to the trap energy is correct in concept, but needs to be carefully calculated for each case.
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