Texture prediction of Bi2Te3 electroplated layers using Hartman's theory of crystal growth

An experimental study of electroplated thin films of bismuth telluride, R3m crystal structure, shows that fibre textures are observed during the growth of the layers. Several orientations 00.1, 10.10, 11.0, 10.4, 10.8, 01.5 and 10.0 are developed during the deposition process, then reach a final orientation. Hartman's theory of crystal growth based on the periodic bond chain (PBC) in a crystal lattice is usually applied. This explains the equilibrium shape of a crystal defined by F faces and the faces observed during the growth (S and K faces). It also successfully predicts the orientations observed in bismuth telluride from the beginning to the end of the layer deposition. The theory may also be applied to other deposition processes.     

Recovery and recrystallization of electrodeposited bright copper coatings at room temperature. II. X-ray investigation of primary recrystallization

X-ray investigations of the recrystallization processes occurring at room temperature in electrodeposited bright copper coatings were carried outin situ. As a result of the orientation transformation of the growth texture with 311, 111 and 110 components, a recrystallization texture with 100, 110 and 111 components was obtained. It was established that one of the factors which influence the microhardness of copper coatings is the orientation distribution of crystallites.     

Theoretical aspects of bonding in silicon compounds

Ab initio-calculated bond dissociation energies of Si=Si and C=C are discussed by means of atomic ionization energies and p-p() AO overlap. At the same time ring strain energies of C- as well as Si-rings are estimated by homodesmic reactions where, according to Baeyer, the two-membered rings C=C and Si=Si are chosen to be the first members of the respective series. Thus, a better understanding of the double bonds can be gained. In addition, the exceptional structural and spectroscopic behavior of the five-membered Si-ring is discussed. Finally, the strikingly different results obtained in computational studies of the initial step for polymerization of the systems O=C=O and O=Si=O are discussed.     

Crystal Orientation Dependence of Macropore Formation in n-Si With Backside-Illumination in HF-Electrolyte

The formation of macropores on anodically biased n-type silicon with backside-illumination was investigated as a function of crystal orientation and bias voltage. Specimens were cut from bulk crystals with various orientations from {100} to {111}, polished and subjected to anodic etching in HF. The resulting pores were investigated on cleaved samples by SEM. All pores were found to grow in either a 100 direction or a 113 direction, depending on the misorientation angle. This finding applies also to the branching of a single pore. The results can be understood if the valence for the dissolution reaction is approximately 2.6 in 100 and approximately 4 in the 113 direction, and if all other directions are not allowed for the growth of pores in Si.     

Nucleation and growth kinetics of Ag7NO11 on a platinum single crystal electrode

The process of electrochemical deposition of Ag₇NO₁₁ on a platinum single crystal anode from 5M AgNO₃ is investigated. The nucleation and growth rates are measured at different constant overpotentials. The orientation of the Ag₇NO₁₁ crystals with respect to the substrate surface is determined in the case of deposition on glassy carbon and on the 100, 111 and 110 faces of a platinum single crystal.     

The effects of antimony and glue on zinc electrowinning from Kidd Creek electrolyte

The individual and combined effects of antimony and glue on zinc deposition current efficiency and polarization and on the morphology and orientation of 6h zinc deposits electrowon at 500 A m^–2 and 38° C from Kidd Creek zinc electrolyte were determined. Glue increased zinc deposition polarization, reduced the deposit grain size, changed the preferred deposit orientation from basal to intermediate, but decreased the current efficiency. At concentrations above 0.02 mgl^–1, antimony had a strong depolarizing effect on zinc deposition resulting in a basal deposit orientation and very low current efficiency. Certain combinations of antimony and glue, however, optimized zinc deposition current efficiency and consistently gave an intermediate 114 112 103 102 101 preferred deposit orientation. A correlation was observed between the current efficiency (CE) and the nucleation overpotential (NOP) for zinc deposition such that the CE was a maximum when the NOP of the initial cell electrolyte was 120–130 mV and when the NOP of the final cell electrolyte was 100–110 mV.     

Pore Propagation Directions in P+ Porous Silicon

A comparative study is presented on the pore propagation directions of porous silicon layers (PSL) formed on p⁺-type substrates of different orientations. PSLs were formed on plain (0 0 1) and (1 1 1) silicon wafers as well as on structured (0 0 1) wafers containing facets of various orientations. During anodization, regular pores follow the 0 0 1 direction on the (0 0 1) planes. While on the (1 1 1) planes fewer regular pores develop and seemingly propagate closely to the 1 1 1 direction. These results indicate that the pores propagate perpendicular to the surface i.e. along the field lines when the surface orientation is either (0 0 1) or (1 1 1).When the silicon surface provided (1 1 0) orientation (Chuang, Collins, and Smith, 1989), or its position is in between the (0 0 1) and (1 1 1) planes then the pores do not propagate perpendicular to the surface but along the 0 0 1 direction.All the phenomena exhibited might be explained by presuming that during formation, the pores propagate along the 1 0 0 directions, and that those 1 0 0 directions are preferred which are closely to the field lines. In PSLs formed on (0 0 1) surfaces the field lines and the 0 0 1 crystallographic direction are coincident. However, in the (1 1 1) oriented wafer where three equally probable 1 0 0 directions exist around the field lines, more irregular structure of PSLs will develop.     

Inhibition and nickel electrocrystallization

The electrocrystallization of Ni is known to be a highly inhibited process. This work gives some conclusions about the nature of the major inhibiting species. All of these species are formed in the catholyte because of the hydrogen codeposition. Depending on plating conditions, mainly pH and current density of metallic deposition, we observe a predominancy of a definite inhibitor which selectively promotes one mode of growth and leads to a deposit exhibiting definite structural properties. A careful structural investigation of Ni deposits obtained from a Watts solution, thanks to both X-ray diffractometry and electron-microscope techniques, leads us to distinguish a free mode of growth, which is characterized by [100] oriented deposits, from several inhibited modes such as 110, [210], 211 and 111. The two latter are stabilized by Ni(OH)₂ while the two former are respectively due to atomic and molecular forms of adsorbed hydrogen.     

Investigation of Morphology of Porous Silicon Formed on N+ Type Silicon

The properties of porous silicon (PS) are closely connected to its morphology, much investigation has been done in order to correlate the morphological characteristics of PS with the anodisation parameters. In this paper the results of morphological analysis of PS formed on N⁺type substrates of 1 0 0 and 1 1 1 orientation are presented. The dependences of the porosity, thickness of PS, density of pores and of the effective surface on the current density are obtained. Interpretation of these results in terms of diffusion layer and energy levels is given, with special attention given to the low current density case.     

Upwind searching for an odor plume is sometimes optimal

A model is presented that suggests that the optimal strategy for an animal walking or crawling on a substrate while searching for the source of a chemical carried by a shifting wind or current may be to move upwind (or against the current). The requirements are that (1) the current direction fluctuates rapidly within a range that exceeds 30 ° on both sides of the mean direction, and (2) the searching animal can move accurately up- or downwind and, once within the influence of the chemical plume, can move efficiently to the source. Under these conditions, an upwind search is shorter (on the average) by 0.9–0.3 of the range of influence of the chemical stimulus. Thus, this strategy is relatively more important when the total search path is short, i.e., when sources are typically close by. The mean length of the downwind search path is given by L _d =d +r[(1/E) + cos ]/2 and the upwind search path by L _u =d +r[(2/E) – (/sin ) – cos ]/2 whered is the starting distance up- or downwind of the source,r is the range of stimulus influence,E is the efficiency with which the searcher moves to the source within the influence of the plume,a is the angle of the maximum extent of wind direction from the mean, and the average, , is taken over all starting positions across the wind direction that lead to search paths that intercept the area swept by the plume.     

Stress Measurement Technique to Monitor Porous Silicon Processing

Macroscopic stress measurements are used to monitor Porous Silicon processing. Silicon wafer of 1 cm resistivity, n-type and 1 0 0 orientation were used as starting material. Porous Silicon layers with a porosity of 57% and a thickness of 85 m, fabricated by electrochemical anodisation, were differently dried, then the evolution of the wafer deflection has been followed with storage time in air. Thermal treatments both in inert and oxidant atmosphere have been performed up to 1000°C. The stress behaviour vs. temperature allows to estimate the hydrogen desorption activation energy.     

Structure and corrosion resistance of electrolytic nickel coatings containing codeposited nonconducting particles

The codeposition of nonconducting silicate particles with different grain size during the plating of nickel coatings with preferential orientation along with 2 1 1 axis is investigated by electron microscopy. The results confirm that small size particles, about 20 nm, are included in the twinning defects, inherent to this orientation, blocking the latter as active dissolution sites. Larger particles, approximately 1.5 m, are included in the bulk of the coating, and cause a continuous redistribution and decrease of the corrosion rate. On the other hand, when particles of 20 nm size are used, an unusual decoration of the twinning plane {111} perpendicular to the substrate, may lead to the elucidation of some theoretical problems related to the initiation of the texture 2 1 1. A dissolution mechanism is proposed, based on the mutual effect of both factors: redistribution of the corrosion current, and blocking of the twinning planes which act as active dissolution centres. This mechanism is confirmed by Corrodkote tests of codeposited nickel coatings.     

Photopolymerization of 2-(dimethylaminoethyl)methacrylate induced by diacetoxyiodobenzene and bis(trifluoroacetoxy) iodobenzene

Summary The title hypervalent iodine compounds are efficient photoinitiators for the polymerization of 2-(dimethylaminoethyl)methacrylate. The polymer is formed in daylight but faster under UV irradiation, with high conversion; its molecular weight M_n is 9×10⁴ daltons. Copolymerization of this monomer with styrene occurs also under similar conditions at a high rate. A free radical mechanism is suggested for these polymerizations.     

Electrodeposition of compositionally modulated Au/Co alloy layers

Au/Co multilayers were electrodeposited from a single bath based on acid citrate, cobalt sulphate and gold cyanide electrolyte. The Taguchi statistical method was used for experiment planning and optimisation. X-ray diffraction (XRD) investigations of the structure showed that the Au deposits exhibited a polycrystalline fcc 1 1 1 structure with an estimated grain size of 7 nm, while the Co deposits exhibited a nano-polycrystalline fcc structure with an estimated grain size ranging between 2 and 28 nm and a strong in-plane texture. The XRD investigation of the multilayer structure also indicated an interface roughness of about 1.5 nm between the Au and Co layers.     

Characterization of poly(diethoxyphosphazene) by size exclusion chromatography and viscometry

Two samples of poly(diethoxyphosphazene) (PDEP) having very different molecular weights have been studied by viscometry and size exclusion chromatography in THF solution. The results obtained, together with light scattering data of these samples, allow the calculation of the Mark-Houwink constants a=0.65 and K=2.5 10^-4 in THF at 25°C. The method of calculation employed takes into account the great polydispersity of the samples. The characteristic ratio of the unperturbed dimensions was also calculated giving C_n = r²_o/n² 18, a value slightly higher than those previously reported for poly(dihexoxyphosphazene), C_n13 and poly (dichlorophosphazene), C_n13.5.     

Phase composition and structure of silver-antimony alloy deposits plated from ferrocyanide-thiocyanate electrolytes

The structure and phase composition of silver-antimony alloy deposits plated from ferrocyanide-thiocyanate electrolytes is investigated. It is shown that the co-deposition of antimony leads to an abrupt decrease of twinning and the formation of perfect orientation of the crystallites in the alloy along the axis 1 1 1. The co-deposition of antimony exerts a depolarization effect upon the plating process of the alloy. At higher antimony concentrations in the electrolyte and higher deposition current both -phase and -phase of the silver-antimony alloy may be formed as well as the pure antimony phase. The concentration regions of antimony in the alloy, within which the different phases are formed and exist, are in agreement with the requirements of the phase diagram. The separate antimony phase is formed at lower antimony concentrations in the alloy than indicated by the phase diagram. The co-deposition of antimony leads to an increase of the crystal lattice parameter of silver and a substantial augmentation of the hardness of the deposited layers.     

The effect of polydispersity on the analysis of optical tracer diffusion experiments

Summary The effect of intramolecular interference on the wave vector dependence of the average tracer diffusion coefficient in a dynamic light scattering experiment from an optically matched ternary system in which the tracer polymer reptates is examined using a Schulz molecular weight distribution and the Debye interference function for random coils. The average tracer diffusion coefficient in a system in which the tracer is polydisperse is shown to vary continually with q. This variation can be quite substantial for moderate polydispersities even in the regime q¯R_g ⁽ⁿ⁾<1. It is shown that a two parameter linear fit of versus q² data will have a negative intercept and that the apparent q power law dependence of the average decay rate will be greater than 2.     

Relationship between preferential adsorption coefficient and intrinsic viscosity in ternary systems

Summary The relation proposed between the preferential adsorption coefficient, , and the intrinsic viscosity, ¦¦ ¦¦=¦¦+AK has been applied in this paper to previously published data. This equation is found to be valid in theta condi tions and far away from them. The obtained results are compared to the ones calculated with the Dondos-Benoit equation.     

Sequential extraction of nine trace elements from sludge-amended soils

Three separate samples taken from particular location of El-Gabal El-Asfar soils treated with composted sludge and irrigated with liquid sludge effluent were compared with untreated soil. These soils were sampled at 5 depths, i.e. 0–15, 15–30, 30–45, 45–60 and 60–75 cm to estimate the forms of nine trace metals in the solid phase. The soils had been amended with sewage sludge and irrigated with sludge liquids for different periods, i.e. 20, 40 and 60 years. The soil samples were fractionated by sequential extraction to estimate the quantities of these metals in exchangeable, sorbed organic, carbonate, and sulfide forms.Data reveal that most of these elements were concentrated (preferential fixation) in the surface layer (0–15 cm), possibly because of the slight decrease in soil apparent density resulting from sludge application. The trace metal contents in exchangeable and sorbed forms of most metals were very low. Sulfide, carbonate and organic forms were shown to be the dominant fractions for most trace metals under study and varied from one element to another. Nevertheless, at least 6 of these metals have a common behaviour.At the longterm addition of sludge application, the predominant metals were: Zn, Fe, Mn, Cr, Ni and Co in sulfide form; Cu in organic form, and Pb and Cd in the carbonate form.     

Interactions between pheromone traps with different strength lures for the pine beauty moth,Panolis flammea (Lepidoptera: Noctuidae)

Catches of malePanolis flammea in traps baited with lures containing 25 g of sex attractant are enhanced when in the proximity of traps baited with 125-g lures. The degree of enhancement is increased as the intertrap distance is decreased, and when the low-dose trap is upwind of the high-dose one. The patterns of alteration in trap catch suggest that moths initially attracted by one lure may divert into other traps, which may be either upwind of the original trap (overshooting), or downwind (undershooting). Overshooting can result in up to fivefold increases in catch and may provide a useful method for estimating the attractant zone of particular lure/trap combinations.