Binding energy of impurity states in an inverse parabolic quantum well under magnetic field

 We have investigated the effects of the magnetic field which is directed perpendicular to the well on the binding energy of the hydrogenic impurities in an inverse parabolic quantum well (IPQW) with different widths as well as different Al concentrations at the well center. The Al concentration at the barriers was always x_max=0.3. The calculations were performed within the effective mass approximation, using a variational method. We observe that IPQW structure turns into parabolic quantum well with the inversion effect of the magnetic field and donor impurity binding energy in IPQW strongly depends on the magnetic field, Al concentration at the well center and well dimensions.     

Electrochemical Polymerization of Aniline at Low Supporting-Electrolyte Concentrations and Characterization of Obtained Films

Conductive polymers of aniline were synthesized in aqueous acidic media such as perchloric, sulfuric, hydrochloric, phosphoric, and trifluoroacetic acids and the effect of supporting electrolyte was investigated. The conductivity of each polyaniline (PAn) sample was determined by the four-probe technique. PAn (H₂SO₄) sample was shown to have the highest conductivity, specifically, 3.55 S cm^–1. The effect of concentrations of monomers and acids on the conductivity of PAn's was studied. It was observed that the conductivity decreased with increasing aniline concentration and increased with increasing sulfuric acid concentration. The conductivities of PAn (CF₃COOH) were also investigated in different supporting electrolytes and highly good increments of its conductivities were obtained. Magnetic properties of the PAn salts were analyzed by Gouy balance measurements and it was found that their conducting mechanisms are of bipolaron nature. From the FTIR analysis it was found that polymerization occurs via the –NH₂ group in a head-to-tail mechanism. The thermal analyses revealed that PAn (HCl) among the PAn salts studied shows the highest thermal stability. Surface analyses of polymers were clarified by scanning electron microscopy. From elemental analysis results, PAn salts were concluded to be in emeraldine structure.     

The reactions of tellurium tetrahalides with triphenylphosphine under ambient conditions

The reactions of tellurium tetrahalides and triphenylphosphine in tetrahydrofuran have been carried out under ambient conditions and afford [(Ph(3)PO)(2)H](2)[Te(2)X(10)] [X = Cl (1), Br (2)] and [(Ph(3)PO)(3)(OH(3)])(2)[TeI(6)] (4). The X-ray structures of 1 and 2 show that they are isostructural and contain discrete [Te(2)X(10)](2-) anions exhibiting octahedral coordination around both tellurium atoms with one shared edge and [Ph(3)POH...OPPh(3)](+) cations that show strong hydrogen bonds (the O...O distances are 2.399 and 2.404 A for 1 and 2, respectively). The compound 4 is built up with discrete octahedral hexaiodotellurate anions and [(Ph(3)PO)(3)(OH(3))](+) cations. The reaction of TeBr(4) and PPh(3) also results in the formation of formally zwitterionic Ph(3)PO(CH(2))(4)TeBr(4) (3). This reaction involves an unprecedented THF ring opening in which the oxygen atom becomes bonded to the phosphorus atom of triphenylphosphine and the carbon atom at the other end of the five-atomic chain becomes bonded to the tellurium atom of TeBr(4). The ring opening of the solvent THF is also taking place in the reaction involving tellurium tetraiodide, as indicated by the formation of C(4)H(8)TeI(2) (5). The reaction may initially lead to Ph(3)PI(2) that reacts with THF yielding Ph(3)PO and ICH(2)(CH(2))(2)CH(2)I. The latter species reacts with elemental tellurium producing 5. Depending on the conditions upon crystallization, two polymorphs of C(4)H(8)TeI(2) (5a and 5b) are observed. While the molecular structures of the two forms are virtually identical, their packing and intermolecular contacts are different. Two further minor products (6a and 6b) were isolated in the reaction of TeI(4) and PPh(3): Both are formally 1:1 adducts of 5 and TeI(4), but they differ considerably in their structures. 6a can be formulated as [C(4)H(8)TeI(+)](2)[Te(2)I(10)(2-)] and 6b as [C(4)H(8)TeI(+)](2)(TeI(3)(+))(2)(I(-))(4). The latter compound exhibits framework similar to that of the tetramers in gamma- and delta-TeI(4).     

Toxic and trace element analysis of surface sediments from the Gulf of Saros by INAA and XRF methods

Some surface sediment samples, collected from 53 sampling sites of the Saros Gulf, were analyzed quantitatively by radioisotope energy dispersive X-ray fluorescence (EDXRF) and instrumental neutron activation analysis (INAA). Results indicated some correlations between Rb and Sr (r = 0.64), Fe₂O₃ and MnO (r = 0.59), Th and La (r = 0.71), Th and Ce (r = 0.64), Th and Sm (r = 0.60), concentration pairs. U and Th results are found to be compatible with those given in the literature for marine sediments.     

Quantification of antimony depth profiles in Sb-doped tin dioxide thin films

Sb-doped SnO(2) thin films, deposited by atomic layer epitaxy (ALE) for gas sensor applications, have been characterized by secondary ion mass spectrometry (SIMS). Quantification of the depth profile data has been carried out by preparing a series of ion implanted standards. Average concentrations determined by SIMS have been compared with Sb/Sn ratios obtained by X-ray fluorescence (XRF) spectrometry and proton induced X-ray emission (PIXE) spectrometry and have been found to be in good agreement. However, a detection limit of 5x10(18) at cm(-3) could only be obtained because of mass interferences. SIMS data show that the ALE technique can be used to produce a controllable growth and doping of thin films.     

Determination of lead concentration and film thickness in electroluminescent calcium sulfide thin films by X-ray fluorescence

Summary For the analysis of electroluminescent thin films, X-ray fluorescence (XRF) provides a convenient method as both the concentration of the dopant and the film thickness can be determined rapidly and non-destructively. An XRF method for the determination of thickness and lead concentration in lead doped calcium sulfide thin films was developed. Calibration standards made of polyvinyl alcohol and gelatin as well as filter paper standards were used. In addition, the applicability of a fundamental parameter program UniQuant was investigated. For comparison, the concentrations of lead and calcium were determined after dissolution by atomic absorption spectrometry. Generally, the correlation between the different methods excluding the use of filter paper standards was satisfactory. When the dopant concentration was very low or very high, however, the fundamental parameter program yielded best results. Determination of thicknesses by XRF was made by comparing the sulfur K intensities of the sample and those of a zinc sulfide standard. A correction factor for molar masses and densities was applied. The thicknesses obtained were compared to those measured with a profilometer after etching and the deviations were found to be less than 10%.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Simple preparation of iron stabilized carboxonium ions. Concurrent complexation,rearrangement and alcohol addition to terminal acetylenes

CpFe(CO)₂[C(OEt)R]BF₄ complexes can be prepared by reaction of CpFe(CO)₂(isobutylene)BF₄ with monoalkylated acetylenes in methylene chloride/ethanol solutions. Methyl propiolate yields methyl trans-2-ethoxy-acrylate, in a reaction catalytic in CpFe(CO)₂(isobutylene)BF₄, and internal acetylenes can be transformed to CpFe(CO)₂(vinyl ether)BF₄ complexes.     

Growth of silicon thin film by LPE on porous silicon bilayers

The fabrication of solar cells based on the transfer of a thin silicon film on a foreign substrate is an attractive way to realise cheap and efficient photovoltaic devices. The aim of this work is to realise a thin mono-crystalline silicon film on a double porous silicon layer in order to detach and transfer it on mullite. The first step is the fabrication of a double porous silicon layer by electrochemical anodisation using two different current densities. The low current leads to a low porosity layer and during annealing, the recrystallisation of this layer allows epitaxial growth. The second current leads to a high porosity which permits the transfer on to a low cost substrate. Liquid Phase Epitaxy (LPE) performed with indium (or In+Ga) in the temperature range of 950–1050°C leads to almost homogeneous layers. Growth rate is about 0.35 μm min⁻¹. Crystallinity of the grown epilayer is similar on porous silicon and on single crystal silicon. In this paper, we focus on the realisation of porous silicon sacrificial layer and subsequent LPE growth. This revised version was published online in July 2006 with corrections to the Cover Date.     

On-line separation of Pu(III) and Am(III) using extraction and ion chromatography

An on-line method developed for separating plutonium and americium was developed. The method is based on the use of HPLC pump with three analytical chromatographic columns. Plutonium is reduced throughout the procedure to trivalent oxidation state, and is recovered in the various separation steps together with americium. Light lanthanides and trivalent actinides are separated with TEVA resin in thiocyanate/formic acid media. Trivalent plutonium and americium are pre-concentrated in a TCC-II cation-exchange column, after which the separation is performed in CS5A ion chromatography column by using two different eluents. Pu(III) is eluted with a dipicolinic acid eluent, and Am(III) with oxalic acid eluent. Radiochemical and chemical purity of the eluted plutonium and americium fractions were ensured with alpha-spectrometry.     

Effects of various washing procedures on the chromium content of human scalp hair

The effects of four wash procedures on the concentration of chromium in a pooled sample of human scalp hair are compared. The wash solutions examined are Triton X-100, sodium lauryl sulphate, acetone, and a mixture (1 + 1) of hexane and ethanol. The plateaux reached for hair chromium concentration are functions of the number of washings, and are characteristic for each wash solution. The wash procedure recommended involves two 20-min washes with aqueous 1% sodium lauryl sulphate solution after a hexane rinse.