Different Conditions Of Deposition Research Articles

Analysis of the vertical distribution of 137Cs and 239,240Pu in waterlogged and non-boggy soils by the sequential extraction method

Mobile capabilities of 137Cs, 239,240Pu and some stable element physicochemical forms were studied in soil layers at a depth of 6–8 cm (maximum concentrations of radionuclides) of non-boggy and waterlogged soil cores sampled on the shores of Lake Bedugnis (Lithuania). Soil samples were acidic with small amount of clay (muscovite). The radionuclide activity concentrations were about 2.5 times higher in non-boggy soil. It was explained by different conditions of deposition of radioactive fallout at these sampling sites and density of the soil samples. The value of the exchangeable fraction of radionuclides is shown to be an indicator of their migration capabilities in the soil. Under anaerobic conditions in waterlogged soil (stagnant pore water conditions) and due to the presence of clay admixture, ∼90% of 137Cs was concentrated in the residual fraction and its mobility was low. 239,240Pu was concentrated mainly in organic matter with rather large exchangeable fractions (∼9.6–∼13.9%). Under oxidizing conditions in non-boggy soil (dynamic pore water conditions in the case of rain), 239,240Pu was mostly concentrated in the oxide fraction. Its exchangeable fractions were less than those in waterlogged soil and, respectively, its mobility was lower. In non-boggy soils, exchangeable fractions of 137Cs were large and varied in the range of 10.1–12.2%, which indicated its high mobility. In the case, 137Cs adsorption by clay materials was reduced and its residual fraction did not exceed 71.3%. The obtained data show that in the area of Lake Bedugnis, the migration capabilities of 137Cs and 239,240Pu change in antiphase.

Zinc-hyperdoped silicon nanocrystalline layers prepared via nanosecond laser melting for broad light absorption

Current techniques for hyperdoping of Si wafer surface by femtosecond laser or ion implantation have encountered several problems for device fabrication, such as severe lattice defects, shallow doping depth, poor electrical activity of impurities, difficult collection of charge carriers, or weak compatibility with present complementary metal–oxidesemiconductor processes. To provide a new way to solve these problems, in this study, Zn-hyperdoped Si layers were prepared on polycrystalline Si substrates by vacuum evaporation and nanosecond (ns) laser melting under different conditions of deposition and laser treatment. As a result, the hyperdoped Si layers of up to micron-level thickness with a broad light absorption (above 90% from the ultraviolet to the visible range and up to 54% for the near-infrared spectrum) and good electrical transport properties (electron mobility of up to 88.5 cm2⋅V−1s−1 and sheet resistance of ~ 100 Ω⋅square−1) were obtained. These hyperdoped Si layers can be flexibly superimposed on the existing Si optoelectronic devices: Such tandem structure avoids the damage of substrate and provides both the layers and substrate properties. In addition, the variation in the microstructural characteristics of the Zn-hyperdoped Si layers consisting of surface and cross-section structures, Zn impurity distribution and concentration, and crystallinity were carefully studied to clarify the relationships between their preparation conditions, microstructures, and physical properties. The results show that a matching between the thickness of Si-Zn deposited layer and the ns-laser irradiation fluence is crucial to achieve a full melting process and to obtain excellent Zn-hyperdoped Si layers. Their near-infrared absorption and electrical transport properties are determined by the combined effects of surface antireflection, Zn-hyperdoping, and nanocrystallization.

Photoconductivities of Nanocrystalline Vanadium Pentoxide Thin Film Grown by Plasma RF Magnetron Sputtering at Different Conditions of Deposition

In this study, the fabrication and characterization of a metal–semiconductor–metal (MSM) visible photodetector based on V2O5 were investigated. The V2O5 thin film was synthesized on n-type Si (100) as substrate by plasma RF-sputtering. The photoconductivity of the nanocrystalline vanadium pentoxide (V2O5|Si) was investigated at the different conditions of deposition (i.e., RF-sputtering power, pressure, and substrate temperature). The photoconductivity measurement of this work was performed in the darkness and under illumination, with applied voltage from a range of 0.1–10 V and illumination intensity 9.8 mW/cm2. I‒V characteristics under illumination showed that the films prepared from on the basis of n-Si have good efficiency and the best is at power 150 W, pressure 0.03 Torr, and temperature 473 K. The fabricated photoconductive detector showed the spectral response (Rλ) value of 0.0783 A W–1, quantum efficiency 18.04%, spectral detectivity D* = 6.984 × 109 cm Hz1/2 W–1 at wavelength 600 nm, and low spectral responsivity in the UV region.

Electron paramagnetic resonance of amorphous hydrogenated carbon grown under different conditions of deposition

Results from electron paramagnetic resonance (EPR) studies of amorphous hydrogenated carbon (a-C:H) obtained on a quartz substrate under different conditions of deposition E/p (where E is the electric field intensity between the electrodes, and p is the pressure of the gas mix in the capacitive chamber) and temperature of the substrate are presented. Correlations between the EPR line amplitude, spin density, and g-factor, and the optical, electrical, and mechanical properties of a-C:H are found.

Fabrication and Photoelectrochemical Properties of CuO/TiO<sub>2</sub> Heterojunction Nanotubes Array Film

In order to improve the visible light response in titania photocatalysts, CuO/TiO2heterojunction nanostructures (CuO-TNT) were proposed and fabricated via the electrochemical process. TiO2nanotubes array (TNT) was first fabricated by secondary anodization, after that the CuO was doped by the electrodeposition. The thin film was characterized by X-ray diffraction (XRD), diffuse reflection spectra (DRS) and field emission scanning electron microscopy (FESEM). Besides, its photoelectrochemical properties were measured in 0.1 M Na2SO3solution. By comparing the results under different conditions of deposition, it was found that the deposition current density was a crucial parameter for controlling the morphology and the photoelectrochemical properties of the samples.

Influence of the growth conditions on the stoichiometry and on the optical properties of titanium oxide thin films prepared by reactive sputtering

Titanium oxide thin films are deposited at room temperature by reactive DC sputtering onto glass and Si (100) substrates. Different conditions of deposition were varied such as sputtering power, deposition time and oxygen partial pressure to study their influence on the titanium oxide thin films growth. The absolute amount of oxygen and the relative O/Ti composition of films have been determined by Nuclear Reaction Analysis and Rutherford Backscattering Spectroscopy, respectively. Additionally, the band-gap was determined by measuring the optical absorption and its behavior correlated with the oxygen film content. From the present study, it is possible to establish that the optical band-gap energy depends mainly on the sputtering oxygen partial pressure used at the preparation and that films prepared with a partial oxygen pressure of 4 × 10 − 2 Pa allows titanium oxide with near stoichiometric composition. Additionally, from the optical point of view, band-gap energies of 3.4 eV are obtained for near stoichiometric films and a decrease is observed for samples prepared with higher oxygen concentrations.

Fe interaction with native SiO2 on Si(001) studied by RHEED

Kinetics of structure and phase constitution of Fe/SiO2/Si(001) system under different conditions of deposition and annealing was considered. It was established that SiO2 layer is not destroyed during Fe deposition process over the temperature range from 20 to 650°C. As a result, the Fe films having different morphologies are formed on the oxide surface. Destruction of SiO2 layer occurs upon annealing on defect places of SiO2 film that results in the interaction of Fe atoms with the Si substrate and successive silicides formation. [DOI: 10.1380/ejssnt.2007.45]

Clay mineralogy of the Cretaceous strata of the British Isles

AbstractThe clay mineralogy of the Cretaceous strata of the British Isles is described and discussed within its lithostratigraphical and biostratigraphical framework using published and unpublished sources as well as 1400 new clay mineral analyses. The regional clay mineral variation is described systematically for the following strata:(1)Southern England — Purbeck Limestone Group (Berriasian/Ryazanian; Lulworth and Durlston formations), Wealden Group (Valanginian—Barremian/Aptian; Ashdown, Wadhurst Clay, Tunbridge Wells Sands, Grinstead Clay Member, Wealden Clay, Wessex and Vectis formations), Lower Greensand (Aptian—Lower Albian; Atherfield Clay, Hythe, Sandgate, Folkestone Sands, Ferruginous Sands, Woburn Sands and Faringdon Sponge Gravels formations), Selborne Group (Middle—Upper Albian; Gault Clay and Upper Greensand formations) and the Chalk Group (Cenomanian—Lower Maastrichtian).(2)Eastern England — Cromer Knoll Group (Ryazanian—Upper Albian; Speeton Clay, Spilsby Sandstone, Sandringham Sands, Claxby Ironstone, Tealby, Roach Ironstone, Dersingham, Carstone and Red Chalk (or Hunstanton Red Limestone) formations).(3)Scotland — Inner Hebrides Group (Cenomanian—Campanian; Morvern Greensand, Gribun Chalk, Coire Riabhach Phosphatic Hibernian Greensands formations).(4)Northern Ireland — Hibernian Greensands (Cenomanian—Santonian) and Ulster White Limestone formations (Santonian—Lower Maastrichtian).The stratigraphical patterns of clay mineral variation divide naturally into two types; firstly, the more complex pattern of the Lower Cretaceous strata and secondly, the simple pattern of the Upper Cretaceous. Clay mineral variations in the non-marine and marine Lower Cretaceous strata of England are best explained by the interplay of two main clay mineral assemblages between which all gradations occur. The assemblage which dominates the main clay formations consists of mica, kaolin and poorly defined mixed-layer smectite-mica-vermiculite minerals, and sometimes includes vermiculite and traces of chlorite. It is dominantly of detrital origin and detailed evidence indicates it is derived largely from the reworking of Mesozoic sediments although ultimately from weathered Palaeozoic sediments and metasediments. Although mainly of detrital origin, this assemblage contains a persistent component that formed coevally with the approximate depositional age of its host sediment. Whether this component is of soil origin or was neoformed in the sediment shortly after deposition is unclear. There is little firm evidence indicating the sources of this clay mineral detritus. However, in the strata of the Wealden Group of southern England, mineral trends suggest three sources; one of these was to the west (Cornubian Massif), another must have been the Anglo- Brabant landmass. In the Selborne Group (Middle—Upper Albian) and in the overlying Lower Chalk (Cenomanian) where this assemblage makes its last appearance in the Cretaceous of England, there is good evidence of easterly and south-easterly sources.The second main assemblage tends to be largely monominerallic, and usually dominated by smectite with or without small amounts of mica; less frequently, kaolin, berthierine or glauconite sensu lato is the sole or dominant component. It is considered to be of volcanogenic origin, derived from the argillization of volcanic ash under different conditions of deposition and diagenesis. The source of the ash in Berriasian—Aptian times seems to have been an extensive volcanic field in the southern part of the North Sea and in the Netherlands, whereas in the Albian (and extending into the Cenomanian) a westerly source dominated. The current controversy about the role of climate or pattern of volcanic activity controlling the clay mineral stratigraphy of the Lower Cretaceous is reviewed.In the lower part of the Upper Cretaceous strata of England, Scotland and Ireland, sand-grade glauconite is particularly abundant. Much of it represents the glauconitization of pene- contemporanous volcanic ash, possibly of basaltic origin, associated with continental breakup and the opening up of the Atlantic Ocean and the earliest stages in the development of the Hebridean Tertiary Igneous Province. The Upper Cretaceous Chalk facies of England and Ireland is dominated by a smectite-rich clay assemblage containing mica, and the various hypotheses for its origin (detrital, neoformation, volcanogenic) are reviewed in the light of available mineralogical, chemical and geological data.

ホローカソード放電法で作製したダイヤモンド状炭素膜および窒化炭素膜の特性評価

Diamond-like carbon (DLC) and carbon nitride (C-N) films have the superior properties of hardness and wear-resistance. They have been investigated extensively for several applications. In this present study, DLC and C-N films were prepared on silicon wafers, stainless steel sheets, high speed steel blocks and WC-Co tips by the hollow cathode discharge method at the high deposition rate of 0.3μm/min. Silicon or tungsten carbide-cobalt was deposited as an interlayer in order to improve the adhesion of DLC and C-N films. Raman spectra of the DLC and C-N films showed distinct D and G bands. The indenting hardness of the C-N films was found to be larger than that of the DLC films. The intensity ratio of the D band to G band in the DLC films related linearly to the indenting hardnesses. On the other hand, the intensity ratios in the C-N films were almost constant in spite of the different conditions of deposition. The indenting hardness in the C-N films depended on the amount of contained nitrogen. The DLC films exhibited a lower friction coefficient compared with the C-N films.

Investigation of composition, optical and electrophysical properties of tin dioxide films made by oxidative pyrolysis of tetraethyltin

Deposition of the transparent electroconductive tin dioxide films was carried out using thermal decomposition of tetraethyltin in oxidative medium at normal and elevated pressure in the reactor of horizontal type. Investigation on the chemical composition, light transmission and electroresistance of SnO 2 films, obtained in different conditions of deposition, are reported. The special features of the etching of the pyrolytic SnO 2 films, aimed to create topological pattern for the electronic devices, were also investigated.

ADSORPTION OF GLYCINE ON Cu(111) INVESTIGATED BY SCANNING TUNNELING MICROSCOPY

The adsorption behaviours of glycine on Cu(111) have been investigated under ultra-high vacuum conditions at room temperature using scanning tunneling microscopy(STM). At lower coverage, it has been found that glycine can form only a two-dimensional gas phase on the Cu(111) surface. When the coverage is high enough, glycine will form a two-dimensional solid phase, i.e., the (4×8) superstructure. Two possible models have been proposed for the (4×8) superstructure. The models can explain STM images well. In addition, in a coverage range between those of the gas and solid phases, two intermediate phases are formed depending on different conditions of deposition and annealing. One is a stripe structure; the other is a hexagonal structure. To understand these intermediate phases further investigations are needed.

Relation Between Deposition Parameters, Structure and Raman Spectra of Carbon Overcoats on Simulated Magnetic Storage Discs

Raman spectra of carbon overcoats of simulated hard magnetic storage discs were obtained for different conditions of deposition by argon ion-induced sputtering. Both an increase of substrate temperature and of argon ion pressure improved the spectral resolution of the two major Raman peaks, one at 1360 cm-1 (the so-called D peak) and one at 1580 cm-1 (the so-called G peak). By fitting these bands to Lorentzian contours and determining their separation it is possible to develop a quality factor from the spectra, which can be empirically related to performance in a disc drive.

Simulation of the step coverage for chemical vapor deposited silicon dioxide

A simulation procedure describing the low-pressure chemical vapor deposition (LPCVD) of silicon dioxide on structured wafer surfaces is introduced. Deposition and step coverage of LPCVD films can be understood by adsorption and desorption of a deposition precursor. Experiments are evaluated to verify the simulation and to determine the sticking coefficient at different conditions of deposition.

Morphological improvement of zinc electrodeposits by laser assistance

Laser assistance can be used to improve the quality of some metallic deposits that are difficult to obtain otherwise. The influence of the laser beam on their morphology is presented in the case of electrodeposition of zinc onto a zinc surface for different conditions of deposition.

Nature of the disordered state of hydrogenated amorphous silicon as revealed by the study of anelastic relaxation behavior

The nature of the disordered state of hydrogenated amorphous silicon is examined for the first time by measurement of anelastic relaxation behavior. It is demonstrated that local structural units and their modifications control the relaxations in these films under different conditions of deposition, aging, and light exposure. Specifically, the light-induced state in this material is shown to be characterized by four distinct relaxations.

Diagenesis of carbonate cements in Permo-Triassic sandstones in the Wessex and East Yorkshire-Lincolnshire Basins, UK: a stable isotope study

Summary The 13 C/ 12 C and 18 O/ 16 O ratios of carbonate cements in Permo-Triassic fluvio-deltaic sandstones differ between the Wessex and East Yorkshire-Lincolnshire Basins. The isotopic data indicate different conditions of deposition and early post-depositional carbonate precipitation which supports petrological and mineralogical studies of the same sandstones focussed on the development of reservoir properties. Isotopic compositions of carbonate cements vary across the Wessex Basin; they indicate early derivation of dissolved carbonate during recrystallization of detrital limestone. Within the basin, calcite cements show little variation in δ 13 C but considerable differences in δ 18 O between early calcrete calcites and isotopically-light later calcites; δ 18 O decreases to values close to isotopic equilibrium with present water while δ 13 C is not in isotopic equilibrium with bicarbonate in present-day brines. Two distinct generations of replacive dolomite, early non-ferroan and later ferroan, are found in the basin centre and have different δ 18 O but similar δ 13 C values. 34 S/ 32 S and 18 O/ 16 O ratios of anhydrite cements could indicate a remote Zechstein source of sulphate or a mixed marine sulphate-sulphide source. The Permo-Triassic sandstones of the East Yorkshire-Lincolnshire Basin, in contrast, contain dominantly dolomite cement. δ 18 O and δ 13 C values are relatively heavy and indicate early dolomitization of calcite over large areas. δ 18 O values of minor calcites indicate that dedolomitization is continuing in the present-day groundwater regime. The isotopic differences between carbonate cements in the two basins is tentatively attributed to the differing early post-depositional conditions and to the differences in carbonate chemistry between calcite dissolution/precipitation reactions and dolomitization reactions.

Interfacial Structure of Tungsten Layers Formed by Selective Low Pressure Chemical Vapor Deposition

We have analyzed the interfacial structure of selectively deposited LPCVD tungsten on monocrystalline silicon, polycrystalline silicon, and polycrystalline aluminum substrates. Cross‐sectional specimens were examined by transmission electron microscopy to determine the amount of substrate consumed by the selective deposition process and to assess the degree of lateral encroachment under masking layers for different conditions of deposition and surface preparation. The tungsten‐silicon interfacial structure was found to depend strongly on the initial surface preparation. Immersion in a dilute solution resulted in a smooth interface, while a glow‐discharge treatment led to highly irregular interfaces, which, in extreme cases, contained tunnels extending 1 μm or more into the silicon substrate. Layers formed in plus were found to consist of two layers, of which the lower layer is formed by the substrate reduction of .

Some fossil psecies of Pediastrum and their palaeoecological significance in the Subathu formation of Himachal Pradesh

Seven new species of the genus Pediastrum Meyen, 1829 have been described from the Subathu Formation (Upper Palaeocene-Eocene), Punjab Basin, Himachal Pradesh. Significance of the morphological characters used for the delimitation of different species has been discussed with a note on the distribution of fossil Pediastrum in the Indian sediments. Comments on the palaeoecological significance of the genus have also been made which highlight its importance in different conditions of deposition.

Mineralogy and the question of zoning, northwestern Illinois zinc-lead district

A detailed study of the mineralogy and paragenesis of the Zn-Pb ores of northwestern Illinois reveals that conditions of ore deposition were the same in the stratigraphically higher deposits as they were in the deeper flat-and-pitch deposits. Except for an increase of galena relative to sphalerite in the crevice deposits, the minerals, their habits, and their relation to one another are the same in the 2 classes of deposits. In addition, spectrographic analyses show no differences in trace element content between samples of the same mineral from the different stratigraphic horizons. It is proposed that the 2 classes of deposits do not represent zones of different conditions of deposition. Two possible causes of the increase of galena in the stratigraphically higher deposits are discussed.

On the Size of the Intermicellar Spaces and Capillaries in Jute Fibers as Revealed by X-Ray Analysis

The dimensions of the intermicellar regions and capillaries in raw jute fibers have been estimated from the sizes of the colloidal gold and silver particles deposited in the fiber under different conditions of deposition. It has been inferred that the dimensions of the colloidal particles indicate only the dimensions of the capillaries after they have been enlarged by swelling or by the deposition process itself. The size of the particles determined is of the order of 100 A in raw jute fiber ; it has been pointed out that they remain within wider capillaries present in jute fiber because the intermicellar region is too small to accommodate these particles. Unlike ramie, in jute fibers treated for a short time with weaker solutions these particles cannot form even within these capillaries. They form within much wider capillaries (about 200 A in diameter), partly because the smaller capillaries are blocked by the noncellulosic amorphous materials (especially lignin) and partly because the swelling of ramie fibers is faster than that of jute fibers having a very high lignin content. This has also been corroborated by the fact that the dimensions of these dispersoids in holocellulose increase to 126 A.