Formation of CdS thin films in a chemical bath environment under the action of an external magnetic field

External magnetic fields were applied during thin film preparation of CdS on glass substrates by the chemical bath deposition technique (CBD). Some physical properties of the polycrystalline films, like layer thickness, grain size and optical quality depend in a characteristic manner on the strength and orientation of the external field during the growth process. The characterization of the samples includes atomic force microscopy (AFM), optical absorption, and dark conductivity measurements. The data interpretation follows a line based on the specific interaction of cadmium and sulfur ions with acting magnetic fields within the chemical bath This article was submitted by the authors in English.     

Impurity and vacancy clustering at the Σ3(1 1 1)[1 −1 0] grain boundary in strontium titanate

The interaction of selected point defects and the Σ3(1 1 1)[1 −1 0] symmetrical twin boundary in SrTiO₃ is investigated by density-functional band-structure calculations. The pristine boundary is SrO₃-terminated and exhibits electronic properties which are comparable with the pure bulk phase. Both the mirror-symmetric twin and some laterally shifted structures have low grain boundary energies, thus they may coexist in a real crystal if external stress is applied. With varying chemical potential of the electrons, the TiO₃ sublattice of the pristine boundary is destabilised by both electron enrichment and electron depletion. These results may explain, why different translation states can be observed by electron microscopy within the same bicrystal.Substitutional doping of the Ti columns next to the boundary plane with formally 3+ cations yields a contraction compared with the pure boundary. The same result, accompanied by more pronounced local geometry changes, is obtained for the translation state in the presence of O vacancies. Neutral O vacancies in the boundary plane are the most stable species followed by positively charged O vacancies in the neighbouring Sr/O plane parallel to the boundary. The Fermi level is shifted either upward to metal-derived states by substitutional doping or downward into the O-2p manifold for O vacancies. These findings may rationalise both the observed low, mainly electronic, grain boundary conductivity of SrTiO₃ boundaries and the changes in local potential found at the grain boundary by tunnelling and force microscopy experiments.     

Optimization of the electrophoretic deposition of YBa2Cu3O7−x superconducting large area coatings

Large area coatings (>10cm²) of the high temperature superconductor YBa₂Cu₃O_7–x (x = 0.1 – 0.2) (YBCO) have been prepared by scale up an electrophoretic deposition technique using silver sheets and Si-wafers coated with Ag or Au as substrates. Several parameters, like the kind of the solvent, the applied voltage, the distance between the electrodes, the initial concentration of the suspension and the temperature during the electrophoresis were investigated in order to attain high deposition rates, as well as uniform YBCO coatings with the proper stoichiometry. To obtain a strongly adherent and dense coating a subsequent appropriate sintering and annealing procedure has been developed. The coatings obtained were characterized for their stoichiometry and superconducting properties by X-ray diffraction (XRD), Raman spectroscopy and magnetic measurements. The homogeneity and thickness of the films and the average grain size of the deposited particles have been investigated by optical and scanning electron microscopy (SEM).     

Nanopatterning of Si(1 1 1) surfaces by atomic force microscope scratching of an organic monolayer

In this work, we demonstrate selective electroless deposition of Cu into nanoscratches produced on n-type Si(1 1 1) surfaces covered with an organic monolayer. The organic layer (undecylenic acid) was covalently attached to a hydrogen-terminated Si surface. The nanosize scratches were produced with an atomic force microscope (AFM) in contact mode using a diamond-coated tip. Copper was deposited in the scratched regions with an electroless (immersion plating) approach using a 0.05 M CuSO₄ + 1% HF electrolyte. The results show clearly that the organic layer can be used as a mask for the deposition of Cu. Optimization of the electrochemical parameters, leads to a very high selectivity and uniform and well-defined nanostructures. This process represents a novel approach for a direct patterning of Si surfaces using an immersion plating reaction.     

Surface morphology of Ge‐modified 3C‐SiC/Si films

The influence of Ge deposition prior to carbon interaction with 3° off‐axis Si(111) substrates on the structural and morphological properties of the formed silicon carbide (SiC) layer is studied. In situ reflection high‐energy electron diffraction (RHEED) and X‐ray diffraction (XRD) revealed the formation of the cubic silicon carbide (3C‐SiC) modification. In situ spectroscopic ellipsometry measurements revealed a decreasing 3C‐SiC thickness with increasing Ge predeposition. Atomic force microscopy (AFM) studies revealed that the surface overlayer morphology is mainly formed by periodic step arrangements whose relevant geometric parameters, i.e. lateral separation, height and terrace width, depend on the Ge content. Besides the changes of the step morphology, the surface roughness and the grain size and the strain of the formed 3C‐SiC decreases with increasing germanium precoverage. Copyright © 2008 John Wiley & Sons, Ltd.     

The effect of magnetic fields on the electrodeposition of iron

The effect of a uniform magnetic field with flux density up to 1 T on the electrodeposition of Fe from sulphate electrolyte has been investigated under different field configurations relative to the electrode surface. Voltammetric and chronoamperometric experiments have been carried out coupled with an electrochemical quartz crystal microbalance for in situ mass change measurements. The structure and morphology of the deposited films were determined by scanning electron microscopy, atomic force microscopy and X-ray diffraction measurements. Results show that, when the magnetic field is applied parallel to the electrode surface, the limiting current density and the deposition rate are increased due to the magnetohydrodynamic effect. The nucleation process is also affected in parallel configuration; the current density of the maximum on the chronoamperograms is decreased, and an additional nucleation step might be observed. This effect is attributed to the hydrodynamic response of the electrochemical system. No significant influence on the electrochemical reaction was observed when a magnetic field was applied perpendicular to the electrode. But in this configuration, the morphology of deposited layers is changed by the magnetic field. The morphology changes are discussed. No effect of the magnetic field on the crystallographic structure was observed.     

Spontaneous deposition of Sn on Au(1 1 1). An in situ STM study

The tin adlayer formed by spontaneous deposition on Au(1 1 1) was characterized by cyclic voltammetry and in situ scanning tunneling microscopy (STM) in sulphuric acid solution. Cyclic voltammetry measurements showed oxidation peaks in the potential range −0.60 ⩽ E/V vs SSE ⩽ 0, which can be ascribed to the dissolution of the Sn adsorbed layer. STM images of the Au(1 1 1)/Sn modified surface showed that tin nucleated both on step edges and on the flat terraces forming two-dimensional islands. The anodic polarization of this modified surface produced the gradual dissolution of the Sn adlayer which was evidenced by the formation of some holes and the reduction of the initial terraces to many small islands. STM images with atomic resolution obtained on these islands displayed an hexagonal expanded atomic structure. After the anodic stripping of this Sn adsorbed layer the images exhibited the typical Au(1 1 1) terraces with a (1 × 1) atomic structure. However, at more anodic potentials another dissolution process was observed producing noticeable changes on the surface morphology which could be ascribed to the dissolution of a Au–Sn surface alloy.     

Electrodeposition and Magnetic Characterization of Iron and Iron–Silicon Alloys from the Ionic Liquid 1‐Butyl‐1‐methylpyrrolidinium Trifluoromethylsulfonate

The electrodeposition of soft magnetic iron and iron–silicon alloys for magnetic measurements is presented. The preparation of these materials in 1‐butyl‐1‐methylpyrrolidinium trifluoromethylsulfonate, [Py_1,4]TfO, at 100 °C with FeCl₂ and FeCl₂+SiCl₄ was studied by using cyclic voltammetry. Constant‐potential electrolysis was carried out to deposit either Fe or FeSi, and deposits of approximately 10 μm thicknesses were obtained. By using scanning electron microscopy and X‐ray diffraction, the microstructure and crystallinity of the deposits were investigated. Grain sizes in the nanometer regime (50–80 nm) were found and the presence of iron–silicon alloys was verified. Frequency‐dependent magnetic polarizations, coercive forces, and power losses of some deposits were determined by using a digital hysteresis recorder. Corresponding to the small grain sizes, the coercive forces are around 950–1150 A m^?1 and the power losses were at 6000 J m^?3, which is much higher than in commercial Fe(3.2 wt %)Si electrical steel. Below a polarization of 1.8 T, the power losses are mainly caused by domain wall movements and, above 1.8 T, by rotation of magnetic moments as well as domain wall annihilation and recreation.     

Synthesis and characterization of preferentially oriented (1 0 0) Pt nanowires

Two types of platinum deposits were obtained by potentiostatic deposition onto Ti substrates, namely platinum black (Pt B) and platinum nanowires (Pt NW) with the latter being achieved through a porous anodic aluminum oxide (AAO) membrane at the solution/substrate interface. Surface characterization of these deposits was performed using scanning electron microscopy (SEM) and cyclic voltammetry (CV) in sulphuric acid solution. Surface properties for Pt NW revealed a predominant presence of (1 0 0) crystallographic planes, not present in Pt B deposit grown in the same conditions. Also, Pt NW exhibits an increased resistance to electrochemically active surface area (EASA) loss upon potential cycling in acidic solution, as compared to Pt B.     

Study of Ultrafine Iron Powders by Atomic Force Microscopy

The particles of ultrafine iron powders obtained by three different methods (electrolytic deposition, reduction in hydrogen flow, and grinding in a planetary ball mill in heptane medium) were studied by the atomic force microscopy and the results were compared with the data of electron microscopy and X-ray diffraction analysis. The shape and size of particles were determined from three-dimensional images obtained by atomic force microscopy, and the grain structure of the particle surface layer was studied by measuring the lateral friction forces.     

Directed assembly of BaFe12O19 particles and the formation of magnetically oriented films

We have studied the preparation of oriented BaFe(12)O(19) films produced using electrophoretic deposition (EPD). Highly anisotropic, platelike BaFe(12)O(19) particles were synthesized under hydrothermal conditions, and from these particles, stable suspensions were prepared in 1-butanol by the addition of dodecylbenzene sulfonic acid as a surfactant. The interplay of the interaction forces between the suspended particles and the forces acting on the particles during the EPD directed the particles' assembly in the plane of the substrate. The most significant effect on the orientation of the films was the diameter-to-thickness ratio of the particles, which was experimentally confirmed with X-ray analyses, electron microscopy, and magnetic measurements. The abnormal grain growth that accompanied the sintering at 1150 °C further improved the overall orientation of the films, which showed highly anisotropic magnetic behavior with a remanent-to-saturation magnetization ratio exceeding 0.8.     

Magnetic property of 1:2 mixture of Co(p-tolsal)2; p-tolsal = N-p-tolylsalicylideniminato,and cyclic pentacarbene–pyridine with S = 10/2 in dilute frozen solution

A cyclic pentadiazo-pyridine ligand, cD5py, was prepared and its photoproduct, cC5py, in a frozen solution was confirmed to be a high-spin polycarbene with S = 10/2. The magnetic property of the 1:2 mixture of Co(p-tolsal)₂; p-tolsal = N-p-tolylsalicylideniminato, and cD5py in a dilute frozen solution after irradiation was investigated by SQUID magneto/susceptometry. In the ac magnetic susceptibility measurements, the in-phase and out-of-phase components (χ′ and χ″, respectively) with frequency dependence were observed, indicating that the 1:2 complex, Co(p-tolsal)₂-(cC5py)₂, had slow magnetic relaxation characteristic of the single-molecule magnet (SMM). From the χ″ versus T plots with various frequencies, the values of activation barrier, U_eff, for the reverse of the magnetism was estimated to be 72 K. In the dc magnetic susceptibility measurements, the magnetic hysteresis loops were observed below 3 K. The value of the coercive force, H_c, depends on the temperature and increases on cooling. The hysteresis loop with H_c = 7.1 kOe was observed at 1.9 K.     

Oriented SrFe12O19 thin films prepared by chemical solution deposition

Thin films of SrFe₁₂O₁₉ (SrM) were prepared from a solution of iron and strontium alkoxides through the chemical solution deposition method on both amorphous (glassy SiO₂), and single crystal substrates (Si(100), Si(111), Ag(111), Al₂O₃(001), MgO(111), MgAl₂O₄(111), SrTiO₃(111)) substrates. The process of crystallization was investigated by means of powder diffraction, atomic force microscopy and scanning electron microscopy. Magnetization measurements, ferromagnetic and nuclear magnetic resonance were used for evaluation of anisotropy in the films. Whilst amorphous substrates enabled growth of randomly oriented SrM phase, use of single crystal substrates resulted in samples with different degree of oriented growth. The most pronounced oriented growth was observed on SrTiO₃(111). A detailed inspection revealed that growth of SrM phase starts through the breakup of initially continuous film into isolated grains with expressive shape anisotropy and hexagonal habit. A continuous film with epitaxial relations to the substrate was produced by repeating recoating and annealing.     

Self-assembly of aromatic molecules over zeolite (0 1 0) surfaces: An AFM and semiempirical study

Self-assembly of pyridine base molecules, pyridine and b-picoline, were observed by atomic force microscopy (AFM) on (0 1 0) surfaces of natural zeolites, heulandite and stilbite, respectively. The molecular array structures of the self-assembled adlayers were determined from the AFM images, and they showed well-ordered, two-dimensional (quasi-) hexagonal lattice structures. Orientations of the molecules within the 2D adlayers were also estimated from the AFM images, and their energetics were calculated by means of a semiempirical molecular orbital method.     

Conversion of poly(ethylene‐alt‐tetrafluoroethylene) copolymers into polytetrafluoroethylene by direct fluorination: A convenient approach to access new properties at the ETFE surface

Direct fluorination of poly(ethylene‐alt‐tetrafluoroethylene) copolymer (ETFE) was carried out on commercially available ETFE films with pure fluorine gas at ambient atmosphere. Reaction temperature was either 95 °C or 150 °C and exposure time was 20 hours. Analysis of the fluorinated samples was performed by attenuated total reflection Fourier transform Infrared, confocal micro‐Raman and ¹H and ¹⁹F magic angle spinning nuclear magnetic resonance spectroscopies, scanning electron microscopy, electron diffraction and X‐Ray photoelectron spectroscopies, contact angle determination, atomic force microscopy and nanoindentation measurements, and compared to those of the virgin ETFE copolymer. Integrity of the bulk materials was verified by investigating the thermal behavior of the polymers by thermogravimetric analysis and differential scanning calorimetry. Evidence for the formation of a homogeneous layer of polytetrafluoroethylene with a thickness of several microns at the surface of the copolymers with no degradation of the materials was observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Combined laser and magnetic field treatment of YFeO<Subscript>3</Subscript>—containing films grown by spray-pyrolysis

Thin films (50–1200 nm) of YFeO₃ were deposited on fused silica substrates by spray-pyrolysis using ethylene glycol solution of Y-Fe(III) citric complexes. The films were post deposition annealed at 750°C in static air for 2 h. Films obtained in this way were afterwards irradiated by a burst mode operated Nd-YAG laser (pulse energy 650 mJ, pulse duration 700 μs, energy density 110 mJ/cm²). The laser’s onset was synchronized with that of a magnetic field pulse of nearly square shape (magnetic induction 0.5 T, pulse duration 900 μs). The samples were placed normally to the direction of the magnetic field. The treatment does not affect the phase composition of the film but significantly increases the crystallite sizes of the phases presenting in the sample. The saturation magnetization of the films decreases as a result of the laser and magnetic field treatment and the coercive force increases by 50%.     

Properties of nanocrystalline electrodeposited CoFeP alloy with low phosphorus content

CoFe and low phosphorus containing (<4 at.%) CoFeP alloy films were electrodeposited from NaH₂PO₂ containing solutions at pH 4 on copper substrates under galvanostatic conditions. At the low phosphorus composition, nanocrystalline CoFeP alloy films are formed. The structure, composition and morphology of the thin films were studied using X-ray diffraction, energy dispersive spectroscopy and atomic force microscopy. The magnetic properties of the film were studied using superconducting quantum interference device magnetometer. The thin film performance features were explained on the basis of microstructural features developed during deposition. Whereas the electrodeposited CoFe alloy thin film exhibited mixed hcp and fcc phase structure in the absence of phosphorus, the low phosphorus containing thin film exhibited an increasing mixed bcc and hcp phase structure as its phosphorus content increases, showing modification in the grain size morphology and magnetic properties. In addition to applied current, the amount of P co-deposited in CoFeP alloy depends on the concentration of NaH₂PO₂ source in the bath. Qualitative analysis of the Tafel slope of CoFe and CoFeP deposition suggests that the presence of P in the CoFe deposit does not affect the mechanism of anomalous deposition of Co and Fe, thereby suggesting that CoFeP deposition is anomalous.     

Structural and electrochemical characterization of sputter-deposited nitrided NiCr alloys

Nickel-based coatings are potential candidates for the protection of electrochemical dissolution of steel surfaces. Such coatings, elaborated by magnetron sputtering in a nitrogen atmosphere, offer good corrosion protection, good adherence as well as stability for metallic structures. NiCr alloys with almost constant composition have been deposited with different nitrogen contents on stainless steel and carbon steel surfaces. The coating uniformity, homogeneity, composition and crystallinity have been studied by scanning electron microscopy, energy-dispersive X-ray spectrometry, atomic force microscopy and X-ray diffraction techniques. The corrosion degradation behavior of all the samples was tested in NaCl and NaCl and CO₂ mixture exposures using electrochemical impedance spectroscopy measurements. Nitrided NiCr alloys on a stainless steel substrate resulted with better adhesion than carbon steel, by delaying the corrosion mechanism when exposed to NaCl and CO₂ solution. A comparison of the corrosion resistive behavior of the substrates (stainless steel, carbon steel) and the coatings is made by using the electrical capacitance concept from a double-layer model for the coating–metal interface.     

Sintering behavior and ionic conductivity of Ce<Subscript>0.8</Subscript>Gd<Subscript>0.2</Subscript>O<Subscript>1.9</Subscript> with a small amount of MnO<Subscript>2</Subscript> doping

A 20% GdO_1.5 doped ceria solid solution with a small amount of MnO₂ doping (≤5% molar ratio) was prepared via the mixed oxide method from high-purity commercial powders with grain size around 0.2–0.5 μm. X-ray diffraction analysis indicated that all the samples exhibited the fluorite structure, and no new phase was found. The data from dilatometeric measurements and scanning electron microscopy observations revealed that 1% Mn doping reduced the sintering temperature by over 150 °C, and enhanced the densification and grain growth. Mn doping has little effect on grain interior conductivity, but a marked deterioration in grain boundary behavior is observed. This leads to a lower total conductivity in comparison with the undoped Ce_0.8Gd_0.2O_2–δ. Therefore, for solid oxide fuel cells (SOFCs) with Mn-containing compounds as electrodes, optimization of electrode fabrication conditions is needed to prevent the formation of a lower conductivity layer at the electrode/electrolyte interface since Mn will diffuse from the electrode side to the electrolyte during fabrication and operation of SOFCs. Electronic Publication     

A possible approach towards spin-polarized transport through single molecule magnets: Mn12 on Au(1 0 0)/Fe(1 0 0)/MgO(1 0 0)

The possibility to use the Au(1 0 0)/Fe(1 0 0)/MgO(1 0 0) system as a substrate for future spin-polarized transport measurements on Mn₁₂ single molecule magnets has been investigated by means of scanning tunneling microscopy and X-ray photoelectron spectroscopy at room temperature. In particular, the stability of the iron layer during a wet chemical preparation of Mn₁₂ monolayers was studied. The results demonstrate that Mn₁₂ can be deposited on Au(1 0 0)/Fe(1 0 0)/MgO(1 0 0) while preserving the metallic nature of the ferromagnetic iron layer which is required as a possible source of spin-polarized electrons in future studies.