Surface Segregation Of Antimony Research Articles

Cathodoluminescence Evaluation of Defect Structure in Hydrothermally Grown ZnO:Sb Nanorods

Cathodoluminescence emission of hydrothermally grown antimony doped ZnO nanostructures with different antimony doping (2.5, 4.8, and 11.8 at%) was studied in a scanning electron microscope (CL-SEM). Incorporation of antimony results in formation of mostly nanorods with low aspect ratio together with some Sb-rich nanoparticles. Transmissibn electron microscopy (TEM) of the Sb-doped samples revealed delaminated {10-10} planes produced by antimony surface segregation. CL spectra of the as-grown samples revealed well defined emission bands centered at 3.2, 2.74 and 2.0 eV, attributed to excitonic recombination, and the so-called blue and yellow emissions, respectively. It was observed that the intensity of the blue emission depends strongly on antimony content, suggesting the formation of point defects on Sb doping. While the yellow emission red-shifted after thermal annealing, either in argon or oxygen atmosphere, the intensity of the blue band decreases considerably; such behavior is explained through the reduction of the population of Zn(i) defects.

Morphology and antimony segregation of spangles on batch hot-dip galvanized coatings

Spangles produced by batch hot-dip galvanizing process have a rougher surface and a greater surface segregation of alloying element compared with those in continuous hot-dip galvanizing line (CGL), owing to the cooling rate of the former is much smaller than that of the later. Therefore, typical spangles on a batch hot-dipped Zn–0.05Al–0.2Sb alloy coating were investigated. The chemical, morphological characterization and identification of the phases on the spangles were examined by scanning electron microscopy (SEM), backscattered electron imaging (BSE), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). The results showed that the coating surface usually exhibited three kinds of spangles: shiny, feathery and dull spangle, of which extensively antimony surface segregation was detected. The nature of precipitate on the coating surface was identified as β-Sb 3Zn 4, The precipitated β-Sb 3Zn 4 particles distributed randomly on the shiny spangle surface, both β-Sb 3Zn 4 particles and dentritic segregation of antimony dispersed in the dendritic secondary arm spacings of the feathery spangle and on the whole dull spangle surface. The dentritic segregation of antimony and precipitation of Sb 3Zn 4 compound are discussed by a proposed model.

Blocking of indium incorporation by antimony in III–V-Sb nanostructures

The addition of antimony to III–V nanostructures is expected to give greater freedom inbandgap engineering for device applications. One of the main challenges to overcome is theeffect of indium and antimony surface segregation. Using several very high resolutionanalysis techniques we clearly demonstrate blocking of indium incorporation by antimony.Furthermore, indium incorporation resumes when the antimony concentration drops belowa critical level. This leads to major differences between nominal and actual structures.

Fundamental reactions controlling anion exchange during mixed anion heterojunction formation: Chemistry of As-for-Sb and Sb-for-As exchange reactions

As-for-Sb and Sb-for-As anion exchange reactions have been investigated by the exposure of GaSb surfaces to As2 and As4 species and by the exposure of GaAs to Sb2, respectively. The effect of surface temperature, anion soak time, and anion species (either As2 or As4) on the chemistry governing the anion exchange reactions during GaAsySb1−y∕GaSb and GaSbyAs1−y∕GaAs heterostructure formation by molecular beam epitaxy is examined. It is found that when GaSb surfaces are exposed to arsenic, the anion exchange reaction competes with the formation of isoelectronic compounds, AsSby, which form clusters precipitating in the GaAsySb1−y∕GaSb heterostructures. The relative amount of GaAs and AsSby depends on the surface temperature, the As soak time, and on the As species, i.e., As2 or As4. We observe specific process conditions that minimize AsSby formation, yielding more abrupt heterojunction interfaces. In the case of the Sb2∕GaAs system, the Sb-for-As anion exchange does not occur to a significant degree, but surface segregation of antimony is found. A chemical model for the As-for-Sb anion exchange reaction is proposed.

Surface segregation of antimony on ferritic single crystals

Antimony has frequently been reported to cause temper embrittlement induced by grain boundary segregation in steels containing both nickel and chromium. In order to study the interdependent segregation behaviour of antimony and nickel and the effect of chromium on segregation of these elements, surface segregation was studied on Fe–25% Cr–2%Ni–0.15%Sb and Fe–2.5%Si–2%Ni–0.15%Sb single crystals. Segregation was investigated by means of Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) in the temperature range between 500 and 650°C. On Fe–25%Cr–2%Ni–0.15%Sb, segregation of antimony leading to surface saturation and cosegregation of nickel are observed on (100), (110) and (111) oriented surfaces. LEED investigations yield a complex domain structure which can be derived from a c(2×2) pattern for the (100) oriented surface and a (1×1) pattern for the (111) oriented surface. On the (110) oriented surface, reconstruction occurs. On Fe–2.5%Si–2%Ni–0.15%Sb, the investigated (100) oriented surface is also saturated with segregating antimony. Cosegregation of nickel occurs, but is weaker than on the crystal containing chromium; thus, chromium intensifies cosegregation of nickel with antimony. The LEED pattern exhibits a complex domain structure which is very similar to the structure observed on the (100) oriented surface of the crystal containing chromium.

Study of Surface Segregation of Antimony on SnO2 Surfaces by Computer Simulation Techniques

We have carried out a computational bulk and surface study of the behavior of Sb(III) and Sb(V) ions on the (110) and (001) surfaces of SnO2. In addition, we have also examined the behavior of the ...

Effect of segregated antimony on the oxidation of Fe–4%Sb single crystals

Antimony surface segregation and its effect on oxidation were investigated on (111) and (110) oriented surfaces of Fe–4%Sb single crystals by means of AES (Auger Electron Spectroscopy) and LEED (Low Energy Electron Diffraction). Oxidation experiments were performed at 300°C and 500°C using oxygen pressures between 1×10 −8 mbar and 5×10 −6 mbar for both sputter cleaned surfaces and antimony saturated surfaces. The presence of antimony on the surface retards or even prevents oxidation for both surface orientations and at both temperatures under investigation. LEED patterns show complex superstructures as a result of oxidation of clean surfaces, while for the antimony saturated surfaces, no additional reflexes were detected at a similar degree of oxidation. Different possibilities to interpret the role of antimony in oxidation are discussed.

Influence of Antimony on the Texture and Properties of 2% Si, 0.3% Al Steel for Non-Oriented Sheet

The effect of additions of antimony (0.05% Sb) to silicon steel on the improvement of the electrical properties of non-oriented steel sheet was investigated. Measurements of surface segregation of Sb were performed under UHV conditions in the temperature range from 450 to 900°C, using AES and TDS. Maximum equilibrium surface segregation of antimony was determined at 700 °C. At higher temperatures, T> 800°C, the desorption of antimony from the surface was measured. The grain boundary segregation was negligible and we can conclude that the texture formation, rich in (100) grains, results from the effect of the orientation dependent surface segregation of Sb. This segregation causes differences in surface energies and the stability of different grains. Controlled surface segregation promotes selective grain growth improving the electrical properties of non-oriented steel sheet.

Orientation dependent surface segregation of antimony on non‐oriented electrical steel sheet

The surface segregation of antimony was studied using AES on a 1.8% Si steel alloyed with different mass contents of Sb (0.052 and 0.1%). The dependency of surface segregation on grain orientation and on the presence of other solute atoms (S. P. C, Al. Si) were investigated under UHV conditions in the temperature range from 450 to 900 °C.The results lead to an explanation for the formation of a texture rich in (100)‐grains in Si steel caused by the presence of Sb. Also grain boundaries were analysed by AES after annealing at 850, 700 and 550 °C for different times. Since the grain boundary segregation was negligible one can conclude that the texture formation results from orientation dependent surface segregation of Sb causing differences in surface energies and stabilities of different grains.

AES studies of antimony surface segregation in non-oriented silicon steel

Antimony surface segregation in decarburized non-oriented silicon steel doped with 0.05 wt% Sb and 0.1 wt% Sb was investigated by a previously developed experimental method, based on Auger Electron Spectroscopy, its kinetics determined in the temperature range from 500 to 850°C. It was found that antimony segregation proceeded with perceivable velocity at 600°C and increased with increasing temperature. The thickness of the equilibrium antimony surface segregation layer reached after 30 minutes of annealing at 700°C was estimated to correspond to a monolayer. From the segregation kinetics and its temperature dependence in the temperature range from 650 to 750°C the diffusion coefficient and the activation energy for antimony diffusion in bulk were also estimated. The influence of antimony on the growth of recrystallized grains is discussed from obtained results.

Surface segregation of antimony in Fe-Si steel for grain oriented sheets

Surface segregation of antimony in a polycrystalline Fe-Si alloy with 0.049 wt% Sb was investigated by Auger electron spectroscopy in the temperature range from 450 to 800°C, and the segregation kinetics of antimony were described. From the surface segregation kinetics and its temperature dependence the bulk diffusion coefficient of antimony and the activation energy were determined in the temperature range from 500 to 600°C.

Concentration transient analysis of antimony surface segregation during Si(001) molecular beam epitaxy

Antimony surface segregation during Si(001) molecular beam epitaxy (MBE) was investigated at temperatures T s = 515−800 ° C using concentration transient analysis (CTA). The dopant surface coverage θ, bulk fraction γ, and incorporation probability σ during MBE were determined from secondary-ion mass spectrometry depth profiles of modulation-doped films. Programmed T s changes during growth were used to trap the surface-segregated dopant overlayer, producing concentration spikes whose integrated area corresponds to θ. Thermal antimony doping by coevaporation was found to result in segregation strongly dependent on T s with θ Sb values up to 0.9 monolayers (ML): in films doped with Sb + ions accelerated by 100 V, θ Sb was less than or equal to 4 × 10 −3 ML. Surface segregation of coevaporated antimony was kinetically limited for the film growth conditions in these experiments.

Orientation dependence of surface structures during antimony segregation to crystallographic low-index iron planes

Surface segregation of antimony in a binary FeSb alloy of ≈ 4wt% Sb content was studied by electron spectroscopic methods. AES, LEED and XPS investigations for samples with low-indexed surface orientations (100), (110) and (111) were performed at 450 to 650°C. A (1 × 1) structure was found for the (111) surface at Sb saturation which occurs at all temperatures. Calibrated Auger measurements show that at this state one atomic monolayer of antimony has segregated to this surface. An imperfect c(2 × 2) structure was observed for a (100) oriented sample. Calibration of the maximum Sb peak height ratio shows that this state corresponds to half a monolayer within a 10% deviation ( θ = 0.55). The (110) surface reconstructs into (111) and (11 1) facets after Sb saturation is attained, as an analysis of the irregular electron energy dependence of the observed LEED beams shows. Further, XPS measurements show that the Sb(3d) binding energies for the facetted state and the (111) plane at saturation are the same, and that the Sb(3d) shift observed during segregation can be explained in terms of segregant-segregant and segregant-substrate interaction.

Effect of temperature during ion sputtering on the surface segregation rate of antimony in an iron–antimony alloy at higher temperatures

AbstractThe surface segregation of antimony in an iron–0.23 at% antimony alloy was studied by XPS. The segregation rate in the temperature range between 800 and 900 K depends on the temperature during sputtering with argon ion of kinetic energy of 1 keV. The sputtering at room temperature or 473 K gives higher values of the segregation rate than those at 673 K. Both cases give the activation energy of 170 kJmol−1 for the surface segregation rate. The segregation of antimony is not observed after the sample is heated at 1000 K.

An X-ray photoelectron spectroscopy study of the surface composition of tin and antimony mixed metal oxide catalysts

The surface composition of tin-antimony mixed oxide selective oxidation catalysts has been found to depend upon heat treatment, the surface becoming progressively enriched in antimony at elevated temperatures. Surface segregation of antimony has been investigated by X-ray photoelectron spectroscopy (XPS) and values obtained for the heats of segregation. The observations are discussed in the context of the nucleation and growth of antimony oxide and tin oxide phases in this system.

Interfacial free energy of copper-antimony alloys

It was suspected that the brittleness of copper-antimony alloys is partly due to a low surface energy caused by segregation of antimony to interfaces in the Gibbs manner. In these experiments the surface and grain-boundary energies and the surface segregation were measured on pure copper and copper alloys containing 0.26, 0.57 and 0.78 at. % antimony. The surface energies were measured on these alloys in the form of wires in a helium atmosphere at 950 °C and as similar results were obtained in a hydrogen atmosphere it was concluded that no serious unwanted surface contamination occurred. The grainboundary energies were deduced from the surface energies by measuring the dihedral angles in an electron microscope. The surface energies were 1770, 980, 950 and 900 ergs/cm 2 and the grain-boundary energies 600, 290, 280 and 320 ergs/cm 2 in order of ascending antimony content. The creep rates of the wires in the surface energy experiments agreed to within a factor of 3/2 with the rate calculated from Herring’s equation for diffusion creep. The surface segregation was measured on copper and the 0.57 and 0.78 at. % antimony alloys after annealing and irradiating in order to detect antimony radioactively. Surface segregation of antimony was found in the two alloys in an amount equivalent to 0.37 monolayer of pure antimony. The surface composition and surface energies are shown to be consistent. Antimony does therefore drastically reduce the surface and grain boundary energies of copper by segregating in the Gibbs manner.