Erbium and Germanium Profiles in Si1 – xGe x Layers Grown by Silicon Sublimation-Source Molecular-Beam Epitaxy in GeH4

The Ge and Er depth profiles in Si_{1 – x} Ge _x layers grown on Si(100) substrates by Si sublimation-source molecular-beam epitaxy in GeH₄ were studied by secondary ion mass spectrometry. The results demonstrate that Ge facilitates Er incorporation into the growing Si–Ge layer. The Er dopant profile becomes sharper with increasing Ge content. The Ge profile also has rather sharp boundaries, indicating that there is no Ge surface segregation, which is attributable to the presence of adsorbed hydrogen, acting as a surfactant.     

Performance-friendly rule extraction in large water data-sets with AOC posets and relational concept analysis

In this paper, we consider data analysis methods for knowledge extraction from large water data-sets. More specifically, we try to connect physico-chemical parameters and the characteristics of taxons living in sample sites. Among these data analysis methods, we consider formal concept analysis (FCA), which is a recognized tool for classification and rule discovery on object–attribute data. Relational concept analysis (RCA) relies on FCA and deals with sets of object–attribute data provided with relations. RCA produces more informative results but at the expense of an increase in complexity. Besides, in numerous applications of FCA, the partially ordered set of concepts introducing attributes or objects (AOC poset, for Attribute–Object–Concept poset) is used rather than the concept lattice in order to reduce combinatorial problems. AOC posets are much smaller and easier to compute than concept lattices and still contain the information needed to rebuild the initial data. This paper introduces a variant of the RCA process based on AOC posets rather than concept lattices. This approach is compared with RCA based on iceberg lattices. Experiments are performed with various scaling operators, and a specific operator is introduced to deal with noisy data. We show that using AOC poset on water data-sets provides a reasonable concept number and allows us to extract meaningful implication rules (association rules whose confidence is 1), whose semantics depends on the chosen scaling operator.     

Zn–Ni/nano-TiO2 composite electrodeposits: surface modifications and protective properties

Zn–Ni composite coatings were obtained by electrochemical co-deposition of TiO₂ nano-particles (mean diameter 21 nm). Zn–Ni alloy coating was also produced under the same experimental conditions for comparison. The surface morphology, crystallographic structure, and the grain size of the deposits were investigated, along with the percentage of the embedded nano-particles in Zn–Ni matrix, as a function of concentration of TiO₂ nano-particles in the bath. As the titania incorporation percentage is increased, a grain refinement in the nanometer region was revealed followed enhanced microhardness values and an improvement of the content of the nickel in the alloy. Annealing of all coatings at 200 °C revealed the crystallization of the matrix accompanied by a decrease of microhardness followed by stability for 24 h. The corrosion behavior of Zn–Ni/nano-TiO₂ composite coatings with various amount of particle content was mainly studied by electrochemical impedance spectroscopy in 3 % NaCl. It was seen that Zn–Ni/nano-TiO₂ composite coatings exhibited higher corrosion resistances comparing to Zn–Ni alloy coating and corrosion protection improved with increasing nano-TiO₂ in coatings.     

Nanostructure Growth in the Ga(In)AsP–GaAs System under Quasi-Equilibrium Conditions

Semiconductors - The formation of nanostructures on the surface of GaAs under quasi-equilibrium conditions in a quasi-closed volume from saturated phosphor and indium vapors in the presence of a Au...     

Electrodeposition Behavior,Physicochemical Properties and Corrosion Resistance of Ni–Co Coating Modified by Gelatin Additive

The effect of gelatin on the microstructure, composition and electroplating mechanism of Ni–Co coating synthesized from sulfate media onto carbon steel substrate was investigated using AFM analysis, SEM/EDS and Electrochemical Quartz Crystal Microbalance (EQCM) coupled with chronopotentiometric measurements. The deposition of gelatin in the coating matrix was found to lower the mass of Ni–Co layers. Moreover, the adsorption of this additive seemed to inhibit the initial nucleation of the Ni–Co electrodeposition, showing homogeneous surface and smaller crystallites. Furthermore, the corrosion performance was studied in 3% NaCl solution by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). After a long immersion into chloride solution, Ni–Co–Gelatin (Ni–Co–Gel) coating showed a good stability and a better corrosion resistance. Therefore, the presence of gelatin additive impacted the crystal size, corrosion resistance and Ni–Co deposits morphology.     

Photoresponse recovery in silicon photodiodes upon VUV irradiation

The spatial homogeneity of the photoresponse is studied for silicon photodiodes based on p-n and n-p junctions a year after their irradiation at a wavelength of 121.6 nm and those based on n-p junctions four years after their irradiation with soft X-rays. It is demonstrated that silicon photodiodes based on p-n junctions exhibit a photoresponse recovery effect on being irradiated at a wavelength of 121.6 nm. No recovery effect is observed for silicon photodiodes based on n-p structures.     

Adsorption of weak bases from the gas phase on organic ion exchangers

The adsorption of dimethyl ether and tetrahydrofurane has been investigated at 150 °C on macroreticular ion exchangers of the styrene-divinylbenzene type containing SO₃H, PO(OH)₂ or P(OH)₂ groups. Dual site adsorption without dissociation is suggested on the basis of the analysis of adsorption isotherms and the investigation of the effect of the number of acid groups on the initial adsorption values. The adsorption coefficients found can be used to express the acid strength of the ion exchangers interacting with gaseous molecules at elevated temperature; the relative logarithmic values for the ion exchangers, respectively, with SO₃H, PO(OH)₂ and P(OH)₂ groups were 0; ?1.64; and ?2.51 (from dimethyl ether adsorption). These results are consistent with those calculated from ethyl acetate adsorption [Komers and Tomanová, Collect. Czech. Chem. Commun.37, 774 (1972)]. On the basis of the adsorption data, the relative basicities of the adsorbed molecules could also be compared.     

Poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) based tissue engineering matrices

In this study, the aim was to produce tissue-engineered bone using osteoblasts and a novel matrix material, poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV). In order to prepare a porous PHBV matrix with uniform pore size, sucrose crystals were loaded in the foam and then leached leaving pores behind. The surface of the PHBV matrix was treated with rf-oxygen plasma to increase the surface hydrophilicity. SEM examination of the PHBV matrices was carried out. Stability of PHBV foams in aqueous media was studied. The pH decrease is an indication of the degradation extent. The weight and density were unchanged for a period of 120 days but then a significant decrease was observed for the rest of the study. Osteoblast cells were then isolated from rat bone marrow and seeded onto PHBV matrices. The metabolization and proliferation on the foams was determined with MTS assay which showed that osteoblasts proliferated on PHBV. It was also found that cells proliferated better on large pore size foams (300–500 m) than on the small pore size foams (75–300 m). Production of ALP was measured spectrophotometrically. The present study demonstrated that PHBV matrices are suitable substrates for osteoblast proliferation and differentiation.     

Semi-insulating GaN:C epilayers grown by metalorganic vapor phase epitaxy using propane as a carbon source

The influence of propane present in a reactor at various stages of GaN growth by metalorganic vapor phase epitaxy (MOVPE) on sapphire substrates on the character of epitaxial process and the properties of epilayers has been studied. Doped GaN epilayers with carbon concentration 5 × 10¹⁸ cm^–3 characterized by high crystalline perfection, an atomically smooth surface, and electric breakdown voltage above 500 V at a doped layer thickness of 4 μm have been obtained.