Field-effect-assisted photoconductivity in PbS films deposited on silicon dioxide

Cataloged from PDF version of article.Lead sulfide (PbS) thin films were deposited from a chemical bath onto SiO2/Si (n-type) substrates. Pseudo-metal-oxide-semiconductor devices were obtained by evaporating source and drain gold electrodes on a PbS surface and aluminum gate electrode on a Si substrate. Field-effect-assisted photoconductivity in the PbS layer was investigated at room temperature, in the 800-2700-nm-wavelength domain for different values and polarities of the drain and gate voltages. The best results were obtained for a positive gate, when both semiconductors are in depletion. An enhancement of about 25% of the photoconductive signal is obtained compared with the case when the gate electrode is absent or is not used. A simple model is proposed that explains the behavior of the dark current and photoconductive signal in PbS film with changing the gate voltage. (C) 2002 American Institute of Physics

Highly (111)-oriented Ge thin films on insulators formed by Al-induced crystallization

Remarkable current-enhanced photoconductivity in oxygen-deficient La7/8Sr1/8MnO3−δ thin film Appl. Phys. Lett. 101, 042413 (2012) Ideal transparent conductors for full spectrum photovoltaics J. Appl. Phys. 111, 123505 (2012) Insights on the influence of surface roughness on photovoltaic properties of state of the art copper indium gallium diselenide thin films solar cells J. Appl. Phys. 111, 114509 (2012) Additional information on J. Appl. Phys

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

Optimization of the Radiation Hardness of Silicon Pixel Sensors for High X-ray Doses using TCAD Simulations

The European X-ray Free Electron Laser (XFEL) will deliver 27000 fully coherent, high brilliance X-ray pulses per second each with a duration below 100 fs. This will allow the recording of diffraction patterns of single molecules and the study of ultra-fast processes. One of the detector systems under development for the XFEL is the Adaptive Gain Integrating Pixel Detector (AGIPD), which consists of a pixel array with readout ASICs bump-bonded to a silicon sensor with pixels of 200 {\mu}m \times 200 {\mu}m. The particular requirements for the detector are a high dynamic range (0, 1 up to 10E5 12 keV photons/XFEL-pulse), a fast read-out and radiation tolerance up to doses of 1 GGy of 12 keV X-rays for 3 years of operation. At this X-ray energy no bulk damage in silicon is expected. However fixed oxide charges in the SiO2 layer and interface traps at the Si-SiO2 interface will build up. As function of the 12 keV X-ray dose the microscopic defects in test structures and the macro- scopic electrical properties of segmented sensors have been investigated. From the test structures the oxide charge density, the density of interface traps and their properties as function of dose have been determined. It is found that both saturate (and even decrease) for doses above a few MGy. For segmented sensors surface damage introduced by the X-rays increases the full depletion voltage, the surface leakage current and the inter-pixel capacitance. In addition an electron accumulation layer forms at the Si-SiO2 interface which increases with dose and decreases with applied voltage. Using TCAD simulations with the dose dependent damage parameters obtained from the test struc- tures the results of the measurements can be reproduced. This allows the optimization of the sensor design for the XFEL requirements

Study of X-ray Radiation Damage in Silicon Sensors

The European X-ray Free Electron Laser (XFEL) will deliver 30,000 fully coherent, high brilliance X-ray pulses per second each with a duration below 100 fs. This will allow the recording of diffraction patterns of single complex molecules and the study of ultra-fast processes. Silicon pixel sensors will be used to record the diffraction images. In 3 years of operation the sensors will be exposed to doses of up to 1 GGy of 12 keV X-rays. At this X-ray energy no bulk damage in silicon is expected. However fixed oxide charges in the insulating layer covering the silicon and interface traps at the Si-SiO2 interface will be introduced by the irradiation and build up over time. We have investigated the microscopic defects in test structures and the macroscopic electrical properties of segmented detectors as a function of the X-ray dose. From the test structures we determine the oxide charge density and the densities of interface traps as a function of dose. We find that both saturate (and even decrease) for doses between 10 and 100 MGy. For segmented sensors the defects introduced by the X-rays increase the full depletion voltage, the surface leakage current and the inter-pixel capacitance. We observe that an electron accumulation layer forms at the Si-SiO2 interface. Its width increases with dose and decreases with applied bias voltage. Using TCAD simulations with the dose dependent parameters obtained from the test structures, we are able to reproduce the observed results. This allows us to optimize the sensor design for the XFEL requirements

The Use of Infrared Spectroscopy in the Investigation of Urolithiasis Ulilizarea spectroscopiei în infraroşu pentru investigarea urolitiazei

Abstract Infrared (IR) spectroscopy is a modern physical-chemical method suitable for the investigation of kidney stones composition. The application of this method in our wor

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

Cryo-EM structure of a helicase loading intermediate containing ORC-Cdc6-Cdt1-MCM2-7 bound to DNA

In eukaryotes, the Cdt1-bound replicative helicase core MCM2-7 is loaded onto DNA by the ORC-Cdc6 ATPase to form a prereplicative complex (pre-RC) with an MCM2-7 double hexamer encircling DNA. Using purified components in the presence of ATP-γS, we have captured in vitro an intermediate in pre-RC assembly that contains a complex between the ORC-Cdc6 and Cdt1-MCM2-7 heteroheptamers called the OCCM. Cryo-EM studies of this 14-subunit complex reveal that the two separate heptameric complexes are engaged extensively, with the ORC-Cdc6 N-terminal AAA+ domains latching onto the C-terminal AAA+ motor domains of the MCM2-7 hexamer. The conformation of ORC-Cdc6 undergoes a concerted change into a right-handed spiral with helical symmetry that is identical to that of the DNA double helix. The resulting ORC-Cdc6 helicase loader shows a notable structural similarity to the replication factor C clamp loader, suggesting a conserved mechanism of action

ИНЖЕКЦИОННЫЙ ОТЖИГ РАДИАЦИОННЫХ ДЕФЕКТОВ МЕЖДОУЗЕЛЬНОГО ТИПА В ЛЕГИРОВАННЫХ БОРОМ КРИСТАЛЛАХ КРЕМНИЯ

Using the same n+–p diode structures, the effect of injection of minority charge carriers on the annealing of various interstitial defects has been studied in silicon irradiated with α-particles. It has been found that the self-interstitial silicon atoms (Sii) possess the highest sensitivity to forward current injection. At a liquid nitrogen temperature and a forward current density of 10–20 mA/cm2, the time constant for Sii annealing is about a few seconds. To activate the interstitial boron atoms at Т ≤ 140 K, substantially higher direct current densities are required (≥ 100 mA/cm2). However, it has been found that the forward current injection not only enhances, but even causes the retardation of interstitial carbon annealing. It is suggested that only the reactions of interstitial atoms, characterized by a strong electron-phonon coupling, can be enhanced by recombination processes.  С использованием одних и тех же n+–p диодных структур проведено изучение влияния инжекции электронов в p-область диода на отжиг в ней простейших дефектов междоузельного типа, созданных облучением α-частицами. Обнаружено, что собственные междоузельные атомы Si обладают наиболее высокой чувствительностью к инжекции. При температуре жидкого азота и плотности прямого тока 10–20 мА/см2 постоянная времени их отжига составляет единицы секунд. Для активации атомов междоузельного бора при Т ≤ 140 К требуются более высокие плотности прямого тока (≥ 100 мА/см2). В отличие от двух предыдущих случаев, пропускание прямого тока через n+–p-переход не только ускоряет, но даже замедляет отжиг междоузельного углерода. Высказано предположение, что только реакции междоузельных атомов, которые характеризуются сильным электрон-фононным взаимодействием, могут быть ускорены в результате рекомбинационных процессов.