Preparation and optical characterization of Cu2ZnGeSe4 thin films

Cu2ZnGeSe4 (CZGSe) films have been fabricated by ion beam sputtering onto glass substrates at a substrate temperature of 300 and 420 K. CZGSe films were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, scanning electron microscopy and by the method of normal incidence transmittance and reflectance. XRD studies reveal an improved crystallinity of the polycrystalline CZGSe films with tetragonal structure when the substrate temperature was increased. The refraction index and extinction coefficient were extracted from the optical measurements. Spectral dependence of the absorption coefficient and the energy band gaps values of CZGSe films were also determinedFinancial supports from IRSES PVICOKEST 269167, MICINN projects (KEST-PV; ENE2010- 21541-C03-01/-02/-03) and FRCFB 13.820.05.11/BF projects are acknowledged. RC also acknowledges financial support from Spanish MINECO within the program Ramón y Cajal (RYC-2011-08521

ОПТИЧЕСКИЕ ХАРАКТЕРИСТИКИ ТОНКИХ ПЛЕНОК ДИОКСИДА КРЕМНИЯ, ПОЛУЧЕННЫХ ПРЯМЫМ ОСАЖДЕНИЕМ ИЗ ИОННЫХ ПУЧКОВ

Influence of fractional pressure of monosilane and argon intermixture and substrate temperature on optical performances of thin-film coatings from the silicon dioxide, received by direct deposition from ion beams on substrates from a glass and silicon with use of the end Hall accelerator as a ion source is investigated. It is positioned, that the magnification of fractional pressure of monosilane and argon intermixture of results in to growth of deposition rate and a refractivity and decrease in an optical transmission of coatings. Rise in substrate temperature promoted improvement of optical performances of silicon dioxide layers that explains magnification of adatoms mobility and chemical interaction boost between silicon and oxygen.Исследовано влияние парциального давления смеси моносилана и аргона и температуры подложки на оптические характеристики тонкопленочных покрытий из диоксида кремния, полученных прямым осаждением из ионных пучков на подложках из стекла и кремния с использованием торцевого холловского ускорителя в качестве источника ионов. Установлено, что увеличение парциального давления смеси моносилана и аргона приводит к росту скорости нанесения и коэффициента преломления и снижению оптического пропускания покрытий. Повышение температуры подложки способствовало улучшению оптических характеристик слоев диоксида кремния, что объясняется увеличением подвижности адатомов и стимулированием химического взаимодействия между кремнием и кислородом

Transitions in bacterial communities along the 2000 km salinity gradient of the Baltic Sea

Salinity is a major factor controlling the distribution of biota in aquatic systems, and most aquatic multicellular organisms are either adapted to life in saltwater or freshwater conditions. Consequently, the saltwater–freshwater mixing zones in coastal or estuarine areas are characterized by limited faunal and floral diversity. Although changes in diversity and decline in species richness in brackish waters is well documented in aquatic ecology, it is unknown to what extent this applies to bacterial communities. Here, we report a first detailed bacterial inventory from vertical profiles of 60 sampling stations distributed along the salinity gradient of the Baltic Sea, one of world's largest brackish water environments, generated using 454 pyrosequencing of partial (400 bp) 16S rRNA genes. Within the salinity gradient, bacterial community composition altered at broad and finer-scale phylogenetic levels. Analogous to faunal communities within brackish conditions, we identified a bacterial brackish water community comprising a diverse combination of freshwater and marine groups, along with populations unique to this environment. As water residence times in the Baltic Sea exceed 3 years, the observed bacterial community cannot be the result of mixing of fresh water and saltwater, but our study represents the first detailed description of an autochthonous brackish microbiome. In contrast to the decline in the diversity of multicellular organisms, reduced bacterial diversity at brackish conditions could not be established. It is possible that the rapid adaptation rate of bacteria has enabled a variety of lineages to fill what for higher organisms remains a challenging and relatively unoccupied ecological niche

Investigation of the process of reactive ion-beam sputtering of gallium arsenide using optical emission spectroscopy

Целью данной работы являлось исследование процесса -реактивного ионно-лучевого распыления арсенида галлия с использованием оптического эмиссионного анализа плазмы в области мишени для определения оптимальных условий формирования собственных оксидов GaAs. Источником ионов являлся плазмотрон на базе ускорителя с анодным слоем, который генерировал поток ускоренных ионов аргона и кислорода с энергией 400–1200 эВ. Мишень была изготовлена из арсенида галлия, легированного теллуром. При распылении GaAs ионами Ar+ в спектре обнаружены интенсивные линии GaI (2874,2 Å, 2943,6 Å, 4033,0 Å и 4172,1 Å), атомарного аргона ArI, ионов аргона, а также линии FeI. Появление линий железа может быть объяснено распылением полюсных наконечников магнитной системы ионного источника. Увеличение ускоряющего напряжения с 1 до 3 кВ приводит к росту интенсивности пиков атомарного галлия GaI (4172,1 Å) в 2,38 раза, линии GaI (4033,0 Å) – в 3,25 раза, линии GaI (2943,6 Å) – в 3,4 раза, линии GaI (2874,2 Å) – в 5 раз. Установлено, что увеличение парциального давления кислорода приводит к резкому уменьшению пиков GaI (4033,0 Å) и GaI (4172,1 Å) из-за химического взаимодействия галлия и кислорода. Распыление в чистом кислороде снижает интенсивность этих пиков в 8 и 5 раз соответственно. Интенсивность пиков атомарного галлия GaI (2874,2 Å) и GaI (2943,6 Å) снизилась в 2 и 1,78 раза соответственно. При наличии положительного потенциала на мишени интенсивность всех линий атомарного галлия монотонно снижается с увеличением потенциала. В эмиссионном спектре были обнаружены линии атомарного кислорода ОI (7774,2 Å) и молекулярных положительных ионов O+2 (6418,7 Å, 6026,4 Å, 5631,9 Å и 5295,7 Å). При наличии положительного потенциала на мишени наблюдалось монотонное снижение интенсивности вышеуказанных линий кислорода. Это свидетельствует об интенсификации процессов химического взаимодействия кислорода с элементами мишени и, соответственно, о снижении свободных активных частиц кислорода.The aim of this work was to study the process of reactive ion-beam sputtering of gallium arsenide using optical emission analysis of plasma in the target region to determine the optimal conditions for the formation of intrinsic GaAs oxides. The ion source was a plasmatron based on an anode layer accelerator (UAS), which generated a stream of accelerated argon and oxygen ions with an energy of 400–1200 eV. The target was made from tellurium doped gallium arsenide. Intense GaI lines (2874.2 Å, 2943.6 Å, 4033.0 Å and 4172.1 Å), atomic argon ArI, argon ions, and also FeI lines were detected in the spectrum upon sputtering of GaAs by Ar+ ions. The appearance of iron lines can be explained by the sputtering of the pole tips of the magnetic system of the ion source. An increase in the accelerating voltage from 1 to 3 kV leads to an increase in the intensity of the peaks of atomic gallium GaI (4172.1 Å) by 2.38 times, the GaI line (4033.0 Å) by 3.25 times, the GaI line (2943.6 Å) 3.4 times, GaI lines (2874.2 Å) 5 times. It was found that an increase in the partial pressure of oxygen leads to a sharp decrease in the peaks of GaI (4033.0 Å) and GaI (4172.1 Å) due to the chemical interaction of gallium and oxygen. Sputtering in pure oxygen reduces the intensity of these peaks by 8 and 5 times, respectively. The intensities of the peaks of atomic gallium GaI (2874.2 Å) and GaI (2943.6 Å) decreased in 2 and 1.78 times, respectively. In the presence of a positive potential on the target, the intensity of all lines of atomic gallium monotonically decreases with increasing potential. In the emission spectrum, lines of atomic oxygen OI (7774.2 Å) and molecular positive ions O+2 (6418.7 Å, 6026.4 Å, 5631.9 Å and 5295.7 Å) were detected. In the presence of a positive potential on the target, a monotonic decrease in the intensity of the above oxygen lines was observed. This indicates an intensification of chemical interaction of oxygen with target elements and, accordingly, a decrease in the free active oxygen particles

OPTICAL PERFORMANCES OF SILICON DIOXIDE THIN FILMS RECEIVED BY DIRECT DEPOSITION FROM ION BEAMS

Influence of fractional pressure of monosilane and argon intermixture and substrate temperature on optical performances of thin-film coatings from the silicon dioxide, received by direct deposition from ion beams on substrates from a glass and silicon with use of the end Hall accelerator as a ion source is investigated. It is positioned, that the magnification of fractional pressure of monosilane and argon intermixture of results in to growth of deposition rate and a refractivity and decrease in an optical transmission of coatings. Rise in substrate temperature promoted improvement of optical performances of silicon dioxide layers that explains magnification of adatoms mobility and chemical interaction boost between silicon and oxygen

Transmittance spectra of Cu2ZnSnS4 thin films

Thin films of the quaternary compound semiconductor Cu2ZnSnS4 (CZTS) were produced by ion beam sputtering at substrate temperatures of 323 K, 423 K, and 573 K. The chemical and structural properties of the thin films were studied by electron microprobe analysis and grazing incidence x-ray diffraction. It was shown that, similarly to the corresponding crystals, the main phase in the thin films was Cu2ZnSnS4 with a tetragonal lattice and the space group l4Їl4Ї . The transmittance spectra near the fundamental absorption edge were used to establish the energies and nature of optical transitions. The energies of crystal-field splitting (Δcr) and spin–orbit splitting (Δso) of the valence band of the Cu2ZnSnS4 quaternary compound were calculated on the basis of the Hopfield quasi-cubic model

Transmittance Spectra of Cu2ZnSnS4 Thin Films

Thin films of the quaternary compound semiconductor Cu2ZnSnS4 CZTS were produced by ion beam sputtering at substrate temperatures of 323 K, 423 K, and 573 K. The chemical and structural properties of the thin films were studied by electron microprobe analysis and grazing incidence x ray diffraction. It was shown that, similarly to the corresponding crystals, the main phase in the thin films was Cu2ZnSnS4 with a tetragonal lattice and the space group l 4 . The transmittance spectra near the fundamental absorption edge were used to establish the energies and nature of optical transitions. The energies of crystal field splitting Dcr and spin orbit splitting Dso of the valence band of the Cu2ZnSnS4 quaternary compound were calculated on the basis of the Hopfield quasi cubic mode

Changes in genetic structure of North American Bythotrephes populations following invasion from Lake Ladoga, Russia

1. We used allozyme electrophoresis to compare Bythotrephes longimanus (Crustacea: Onychopoda: Cercopagididae) from recently founded North American populations with those from native European populations, and to examine changes in genetic structure of North American populations over time. 2. The genetic structure of North American populations in 1996 was similar to that of European populations, because of the disappearance of founder effects which distinguished North American from European populations in 1989. 3. The Lake Ladoga, Russia population was more closely related to North American populations than to other European populations, consistent with non-genetic evidence implicating Lake Ladoga as the source of North American populations. 4. Our results provide additional evidence of the presence of an invasion corridor that allows Urasian and Ponto-Caspian species to be introduced into North American freshwater ecosystems, and show that founder effects can erode over time following establishment of invasive species

Functional response of midsummer planktonic and benthic communities in the Neva Estuary (eastern Gulf of Finland) to anthropogenic stress

Long-term hydrobiological research has shown that the functioning of the ecosystem of the Neva Estuary, one of the largest Baltic estuaries, has changed greatly since the beginning of the 20th century. Ineffective local water management in St. Petersburg during thelast twenty years has stimulated the development of a natural "biological plug" in the salt barrier zone in the inner part ofthe estuary and has altered the ecosystem's functioning. These changes include an increase in primary production, in the primary production:organic matter decomposition ratio, and in pelagic-benthic coupling. It has also given rise to filamentous algae blooms and intensive secondary pollution in the coastal zone of the Neva Estuary. The primary production of phytoplankton in the inner part of the estuary has reached 2.3 gC m^-2, that of the filamentous algae <i>Cladophora glomerata</i> 5.5 gC m^-2 these figures are much higher than in other regions of the Gulf of Finland

Preparation and optical characterization of Cu2ZnGeSe4 thin films

Cu2ZnGeSe4 (CZGSe) films have been fabricated by ion beam sputtering onto glass substrates at a substrate temperature of 300 and 420 K. CZGSe films were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, scanning electron microscopy and by the method of normal incidence transmittance and reflectance. XRD studies reveal an improved crystallinity of the polycrystalline CZGSe films with tetragonal structure when the substrate temperature was increased. The refraction index and extinction coefficient were extracted from the optical measurements. Spectral dependence of the absorption coefficient and the energy band gaps values of CZGSe films were also determinedFinancial supports from IRSES PVICOKEST 269167, MICINN projects (KEST-PV; ENE2010- 21541-C03-01/-02/-03) and FRCFB 13.820.05.11/BF projects are acknowledged. RC also acknowledges financial support from Spanish MINECO within the program Ramón y Cajal (RYC-2011-08521