Comparison of near-interface traps in Al2_2O3_3/4H-SiC and Al2_2O3_3/SiO2_2/4H-SiC structures

Aluminum oxide (Al2O3) has been grown by atomic layer deposition on n-type 4H-SiC with and without a thin silicon dioxide (SiO2) intermediate layer. By means of Capacitance Voltage and Thermal Dielectric Relaxation Current measurements, the interface properties have been investigated. Whereas for the samples with an interfacial SiO2 layer the highest near-interface trap density is found at 0.3 eV below the conduction band edge, Ec, the samples with only the Al2O3 dielectric exhibit a nearly trap free region close to Ec. For the Al2O3/SiC interface, the highest trap density appears between 0.4 to 0.6 eV below Ec. The results indicate the possibility for SiC-based MOSFETs with Al2O3 as the gate dielectric layer in future high performance devices.Comment: 3 figures. Applied Physics Letters, accepted for publicatio

RESEARCH ON THE INFLUENCE OF IRRIGATION ON THE BIOCHEMICAL COMPOSITION OF FRUITS SWEET PEPPER IN THE CONDITIONS OF SANDY SOILS IN SOUTHERN OLTENIA

The role of water in plant life is particularly important if it is taken into account that all biological processes can only take place in the presence of water. Using water, translocation of nutrient ions from the soil into the plant and the assimilated substances from the leaf to the fruit and the other organs of the plant takes place. Sweet pepper is a great water consumer, has higher requirements than tomatoes. This high water consumption can also be justified by the temperature requirements during vegetation, therefore it also has a greater sweat. In order to determine the biochemical composition of the sweet pepper fruits, autochthonous varieties was studied in the conditions of thermal stress and water stress from CCDCPN Dăbuleni. The irrigation regime influences the total production of the sweet peppervarieties studied, as well as their biochemical composition. The best results on the biochemical composition were obtained in the Amaradia variety (11.23% total dry matter, 7.8% soluble dry matter, 6.50% carbohydrates and 115.28 mg C vitamin) in the irrigated version with the minimum ceiling .Analyzing the influence of the irrigation ceiling on the biochemical composition of the fruit, it was found that the best results were obtained at irrigation at the minimum ceiling. The greatest difference can be seen in the C vitamin content, which drops a lot in the irrigation option at the technological ceiling (from 103.85mg to 30.87mg). The production results have highlighted the role of irrigation in obtaining productions sweet pepper economically efficient. In normal irrigation, all cultivars recorded large yields over 40.0 t / ha, the Andrada variety recording 55.09 t / ha, with a difference from the statistically insured witness Between the amount of total dry substance in sweet pepper and production, correlations have been established depending on the irrigation variant. In the irrigated version at the minimum level, the dry matter content of the fruit increases with the increase of the production, and in the irrigated variant at the technological ceiling, the total dry substance content decreases with the increase of the production

Metal-Ferroelectric-Metal heterostructures with Schottky contacts I. Influence of the ferroelectric properties

A model for Metal-Ferroelectric-Metal structures with Schottky contacts is proposed. The model adapts the general theories of metal-semiconductor rectifying contacts for the particular case of metal-ferroelectric contact by introducing: the ferroelectric polarization as a sheet of surface charge located at a finite distance from the electrode interface; a deep trapping level of high concentration; the static and dynamic values of the dielectric constant. Consequences of the proposed model on relevant quantities of the Schottky contact such as built-in voltage, charge density and depletion width, as well as on the interpretation of the current-voltage and capacitance-voltage characteristics are discussed in detail.Comment: 14 pages with 4 figures, manuscript under revision at Journal of Applied Physics for more than 1 year (submitted May 2004, first revision September 2004, second revision May 2005

Competition between ferroelectric and semiconductor properties in Pb(Zr0.65Ti0.35)O-3 thin films deposited by sol-gel

Asymmetric metal–ferroelectric–metal (MFM) structures were manufactured by sol–gel deposition of a lead zirconate-titanate (PZT with Zr/Ti ratio 65/35) film on Pt-coated Si, with a Au top electrode. The average remnant polarization of 9 µC/cm2 and the coercive field of 39 kV/cm were obtained from the hysteresis loop measurements. A detailed analysis of the polarization–electric field (P–E), capacitance–voltage (C–V), and current–voltage (I–V) measurement results allowed us to estimate the near-electrode space-charge region thickness (roughly half of the film thickness at zero voltage), net doping concentration (around 1018 cm–3), built-in potential (in the 0.4–0.8 V range, depending on the injecting electrode), and dynamic dielectric constant (5.2). The current logarithm–voltage dependence for the field-enhanced Schottky emission obeys a "1/4" law. The spectral distribution of the short circuit current measured under continuous light illumination in the 290–800 nm range exhibits a cutoff wavelength at 370 nm and a maximum sensitivity at about 340 nm. The estimated band-gap energy of the PZT material is 3.35 eV. The MFM structure is discussed in terms of two back-to-back Schottky diodes with a ferroelectric material in between. It is concluded that the semiconductor properties of the films are not negligible and, in certain conditions, are dominating over the ferroelectric one

Cryo-EM analysis of Ebola virus nucleocapsid-like assembly

This protocol describes the reconstitution of the filamentous Ebola virus nucleocapsid-like assembl

Influence of long-range dipolar interactions on the phase stability and hysteresis shapes of ferroelectric and antiferroelectric multilayers

Phase transition and field driven hysteresis evolution of a two-dimensional Ising grid consisting of ferroelectric-antiferroelectric multilayers that take into account the long range dipolar interactions were simulated by a Monte-Carlo method. Simulations were carried out for a 1+1 bilayer and a 5+5 superlattice. Phase stabilities of components comprising the structures with an electrostatic-like coupling term were also studied. An electrostatic-like coupling, in the absence of an applied field, can drive the ferroelectric layers towards 180º domains with very flat domain interfaces mainly due to the competition between this term and the dipole-dipole interaction. The antiferroelectric layers do not undergo an antiferroelectric-to-ferroelectric transition under the influence of an electrostatic-like coupling between layers as the ferroelectric layer splits into periodic domains at the expense of the domain wall energy. The long-range interactions become significant near the interfaces. For high periodicity structures with several interfaces, the interlayer long-range interactions substantially impact the configuration of the ferroelectric layers while the antiferroelectric layers remain quite stable unless these layers are near the Neel temperature. In systems investigated with several interfaces, the hysteresis loops do not exhibit a clear presence of antiferroelectricity that could be expected in the presence of anti-parallel dipoles, i. e., the switching takes place abruptly. Some recent experimental observations in ferroelectric-antiferroelectric multilayers are discussed where we conclude that the different electrical properties of bilayers and superlattices are not only due to strain effects alone but also long-range interactions. The latter manifests itself particularly in superlattices where layers are periodically exposed to each other at the interfaces

Synthesis of New Methionine Derivatives for the Treatment of Paracetamol - Induced Hepatic Injury

The direct pharmacological properties of amino acids and the possibility of using them as carriers for other active pharmacological substances are well known. Methionine, being able to yield the methyl group, is very important in the treatment of hepatic diseases. Paracetamol acute poisoning causes liver injury in both humans and animals. The study is designed to synthesize some new methionine derivatives and to establish a possible correlation between the new structure and the pharmacological properties. To this end, acute experimental poisoning with PanadolВ® (paracetamol) was performed while, for the treatment of liver injury caused by this compound, two original synthesis derivatives of methionine, namely N-(m-nitrobenzoyl)- L-methionine and N-(m-aminobenzoyl)-L-methionine, were used. Male Wistar rats were administered PanadolВ® (paracetamol) per oral (7500 mg/kg). N-(m-nitrobenzoyl)-L-methionine (m-NBM) 50 mg/kg and N-(m-aminobenzoyl)-L-methionine (m-ABM) 50 mg/kg were given intraperitoneally, 30 minutes after PanadolВ® administration. Biochemical parameters such as SGOT, SGPT, serum bilirubin and glycemia were estimated to assess the liver function. PanadolВ® (paracetamol) poisoning produced an increase in serum transaminases, bilirubin and glicemia. These effects were reduced by treatment with m-NBM and especially m-ABM. These biochemical observations were supplemented by histopathological examination of liver sections. The results obtained with m-ABM were comparable with those reported on methionine, which is a recognised antidote in paracetamol poisoning