Growth and characterization of copper nanoclusters embedded in SiC matrix

Nanocrystalline copper clusters embedded in silicon carbide were made by island growth during sputter deposition. The distribution and morphology of metal clusters were observed by high-resolution transmission electron microscopy. To investigate chemical bonding at the copper-silicon carbide interface, we studied the electronic states of copper and silicon using X-ray photoelectron spectroscopy (XPS). It was found that the formation of copper silicide was suppressed in this system and that small shifts in binding energy were observed for different sizes of clusters, which was different from the chemical shift for copper silicide formation.     

Submonolayer and single crystal film from ligand-stabilized silver nanoparticles

Ligand-stabilized silver nanoparticles were synthesized by a method of ultraviolet light irradiation reduction from a parent solution containing inorganic silver salt, then deposited on carbon coated copper microscope grid by electrophoretic technique. All samples were examined on transmission electron microscope. The results indicate that when the parent solution was irradiated for 5 min a submonolayer of silver nanoparticles was obtained; however, when the parent solution was irradiated for 10 min single crystal silver films were formed. The mechanisms about formation of the submonolayer of nanoparticles and the single crystal silver films were discussed.     

Nickel particle embedded aluminium matrix composite with high ductility

Nickel particulate reinforced aluminium matrix composite was processed without formation of deleterious Al₃Ni intermetallic by friction stir processing (FSP). FSP resulted in uniform dispersion of nickel particles in the aluminium matrix with excellent interfacial bonding and also lead to grain refinement of the matrix. The composite exhibited a threefold increase in the yield stress (0.2% proof stress). The most novel feature of the composite is that an appreciable amount of ductility is retained while the strength increases significantly. The microstructure evolution was studied by transmission electron microscopy and electron backscattered diffraction analysis. EBSD analysis showed a dynamically recrystallized equiaxed microstructure having a considerable fraction of low-angle boundaries. TEM observations revealed that these low-angle boundaries are essentially subgrain boundaries formed by dislocation rearrangement and absorption during friction stir processing.     

Quantitative Analysis of Colour Rendering in Graphic Arts with Three-Colour Printing by Way of Various Photographic Techniques

Various methods of reproduction usual in the graphic arts industry are compared as to their colour-rendering qualities. The methods of reproduction examined differ according to the nature and the number of their intermediate photographic steps. Colour rendering results were obtained by a combination of experimental methods and calculation. The reproduction methods are compared for the case of a perfect grey reproduction, wherein use is made of a definite set of three-colour printing inks.     

Transmission electron microscope study of the topotactic reaction of (0 0 1), (0 1 1) and (1 1 1) Ag films and Te

The formation, structure and morphology of silver telluride was investigated in the reaction of (0 0 1), (0 1 1) and (1 1 1) single crystalline Ag films with vacuum deposited Te. Silver films 30–40 nm in thickness were deposited by thermal evaporation onto water- and chlorine-treated NaCl. Onto this silver 1–40 nm of tellurium were deposited at 100 and 200 °C. The Ag–Te reaction occurred during Te deposition. Accordingly, formation of the compound phase was investigated from the nucleation stage through complete tellurization on either side of the polymorphic phase transformation temperature (T_c=150 °C). Transmission electron microscope and selected area electron diffraction showed that monoclinic silver telluride (Ag₂Te) of different morphology and texture was always formed. The orientation of silver and monoclinic phase upon differently oriented monocrystalline Ag films and at deposition temperatures around T_c is discussed.     

Investigation of the local electron emission from current-carrying silver nanoparticle films by an emission electron microscope

Emission electron microscopy was used to study the electron emission observed under the passage of a tunnel current through a silver nanoparticle film when a voltage is applied to it. The electron emission originates from separate emission centers emitting photons as well. The electron emission centers are visualized as separate spots in an emission electron microscope. A deformation of shape and size of these spots was studied at various applied voltages. It enables the energy spread of electrons emitted from an individual emission center or at least the width of its most intensive part ε as well as the magnitude of electric field E near this center to be estimated. It has been shown that ε comprises 0.5-0.6 eV, and E < < 10⁷ V/cm. The latter result means that the electron emission is not the field emission.     

Characterisation of dislocations, nanopipes and inversion domains in GaN by transmission electron microscopy

Transmission electron microscopy is used to analyse a range of defects observed in hexagonal GaN films grown on sapphire and GaN substrates by metalorganic chemical vapour deposition. Large angle convergent beam electron diffraction is used to analyse the Burgers vectors of dislocations and to show that hollow tubes, or nanopipes, are associated with screw dislocations having Burgers vectors±c. Weak-beam electron microscopy shows that dislocations are dissociated into partials in the (0001) basal plane, but that threading segments are generally undissociated. The presence of high densities of inversion domains in GaN/sapphire films is confirmed using convergent beam electron diffraction and the atomic structure of the {

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} inversion domain boundary is determined by an analysis of displacement fringes seen in inclined domains.     

Incorporation of InAs nanostructures in a silicon matrix: growth, structure and optical properties

MBE growth and properties of InAs nanoscale islands formed on silicon are reported. Islands capped with Si emit a photoluminescence band in the 1.3 μm region. Upon annealing at increased substrate temperature, extensive interdiffusion leads to the formation of an InAs solid solution in the Si cap layer. Additionally, InAs-enriched regions with extensions of 6 nm, exhibiting two kinds of ordering, are observed. The ordering of InAs molecules occurs, respectively, in (101) and planes inclined to (110) and planes parallel to the [001] growth direction.     

Raman study of stress effect on Ge nanocrystals embedded in Al2O3

Ge nanocrystals (NCs) embedded in Al₂O₃ were grown by RF-sputtering. X-ray diffraction, high resolution transmission electron microscopy, and Raman spectroscopy techniques were used to characterize the stresses on the NCs. While small NCs (< 10 nm) have been observed to be spherical and fully relaxed in the matrix, the larger ones (> 17 nm) demonstrated a compressive stress effect. This could be linked to the crystal structure of the adjacent Al₂O₃ matrix.     

Cr3C2 incorporation into an Inconel 625 laser cladded coating: Effects on matrix microstructure,mechanical properties and local scratch resistance

There is an increasing industrial demand for metal alloys with high wear resistance under severe operating conditions. Ni-based alloys, such as Inconel superalloys, are an excellent option for these applications; however, their use is limited by their high cost. Ni-based coatings deposited onto carbon steel substrates are being developed to achieve desired surface properties with reduced cost. Laser cladding deposition has emerged as an excellent method for processing Ni based coatings. In this work, microstructure, mechanical properties and local wear behaviour have been investigated in response to the addition of Cr₃C₂ ceramic particles into an Inconel 625 alloy deposited onto a ferritic steel substrate by laser cladding. Using this deposition technique, a homogeneous distribution of Cr₃C₂ particles was observed in the coating microstructure. The addition of ceramic particles to the starting powder resulted in the formation of hard precipitates in the coating microstructure. The partial dissolution of Cr₃C₂ particles during the laser cladding process increased the hardness of the Inconel 625 matrix. Depth sensing indentation and scratch tests were performed to study the local wear behaviour and scratch resistance of the cermet matrix compared with the conventional Inconel 625 alloy. Finally, the effect of Cr₃C₂ on mechanical properties was correlated with the observed microstructure modifications.     

Effective holographic recordings in the photopolymer nanocomposites with functionalized silica nanoparticle and polyurethane matrix

Effective holographic nanocomposites were developed by the surface-functionalized silica nanoparticles and two acrylate monomers/polyurethane (PU) matrix polymer. The functionalization was done with silane compounds carrying long alkyl chain or vinyl group. We evaluated the holographic nanocomposite films by the diffraction efficiency, volume shrinkage, optical loss, and the film morphology. It was found that acrylate monomers/PU system gave higher diffraction efficiency than those of two monomers due to the high refractive index mismatch between the acrylate-rich and PU-rich regions. With the modification of silica particle, up to 35% of particle loading was possible to give a maximum diffraction efficiency of 93.6% for a film of 20 μm in thickness, along with improved refractive index modulation and the sensitivity.     

Vertical dislocations in Ge films selectively grown in submicron Si windows of patterned substrates

The structural properties of straight screw dislocations extended in the [001] direction formed in squared- and line shaped- Ge(001) films selectively grown on submicron regions of Si(001) substrates were investigated by transmission electron microscopy. The screw dislocations propagating as a result of spiral surface growth were redirected toward the SiO₂ sidewalls. This redirection is linked to the formation of facets such as {111} facets in the growing Ge films. In the process of strain relaxation upon annealing, the screw dislocations were dissociated into dislocations with Burgers vectors of the a/2<110> type, which glided on the {111} surfaces and disappeared.     

Preparation of triangular and hexagonal silver nanoplates on the surface of quartz substrate

In this paper, triangular and hexagonal silver nanoplates were prepared on the surface of quartz substrate using photoreduction of silver ions in the presence of silver seeds. The obtained silver nanoplates were characterized by atomic force microscopy and UV–vis spectroscopy. It was found that the silver seeds played an important role in the formation of triangular and hexagonal silver nanoplates. By varying the irradiation time, nanoplates with different sizes and shapes could be obtained. The growth mechanism for triangular and hexagonal nanoplates prepared on quartz substrate was discussed.     

Mechanism of droplet generation in silver thin films for organic light-emitting diode displays

Thin silver film is widely used as the cathode in organic light-emitting diode displays and it is generally fabricated using the thermal evaporation method. But during the evaporation process, there is an inevitable outgassing problem and this creates high viscosity bubbles in melted silver. When the bubbles break, the high energy released scatters silver droplets which damage the silver surface. In this study, we were able to decrease the number of droplets from 6,171 to 278 with a degassing process of 400 °C for 6 h before proceeding with a thermal evaporation process.     

Comparison of biasing effects between sodium metaphosphate and silver metaphosphate glasses

Comparison is made between sodium metaphosphate glass and silver metaphosphate glass with regard to electrical response to biasing with a dc pulse train. Both glasses show polarization and depolarization peaks at the onsets of biasing and off biasing, respectively. The polarization for the former glass is 2×10⁻⁶ C cm⁻² while it is one order of magnitude less for the latter. Besides, the relaxation time for the former is several orders of magnitude longer than that of the latter. The origin of these differences is discussed. Finally, some insight is given into the question why a silver-conducting glass as silver metaphosphate is far more conductive than an alkali-conducting glass as sodium metaphosphate.     

Growth of nanocomposite in eutectic Cu-Ag films

Eutectic composition Cu-Ag alloy thin films were prepared by co-deposition at room temperature onto oxidized Si substrates by thermal evaporation. Morphological development, structure and phase state of the films were investigated by transmission electron microscopy. The films possess fibre morphology 10-30 nm in diameter and strong <111> texture is present. The fibres are nanocrystalline composed of 2-3 nm size zones of Cu and Ag rich solid solution phases and a model for morphological development and phase separation is described. In the early stages of growth phase separation occurs by nucleation in melted islands and a eutectic of randomly oriented crystallites forms. In later stages of growth the phase separation takes place by spinodal decomposition. It results in a strain stabilized unique morphology corresponding to an intermediate stage of phase separation.     

Antibacterial effects of biosynthesized silver nanoparticles using aqueous leaf extract of Rosmarinus officinalis L.

In this study, we demonstrate a green approach for the synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Rosmarinus officinalis under ambient conditions. The uniqueness of this method lies in its rapid synthesis within 15 min. The synthesized AgNPs were characterized using UV–vis, FTIR, XRD, FE-SEM coupled with EDX, TEM and AFM. The synthesized particles were found to be 14.20–42.42 nm with face centered cubic geometry. The functional group of flavonoids and terpenoids was largely identified by FTIR which was found to be responsible for the synthesis and stabilization of the AgNPs. Further, antibacterial efficacy of the biologically synthesized AgNPs was investigated by the standard method against Pseudomonas aeruginosa and Staphylococcus aureus. The results showed that the aqueous leaf extract mediated synthesized AgNPs is an excellent antibacterial agent against clinical pathogens.     

Optical and morphological characterisation of a silver nanoparticle/fluorescent poly(phenylenethynylene) composite for optical biosensors

Thiol silver nanoparticles prepared by the phase transfer method have been mixed with a fluorescent poly(phenylenethynylene) sequenced with dithioester-diethylsulfide moieties in order to develop a nanocomposite for its possible application in optical biosensors for the detection and attack of fungi such as Paecilomyces variotii. Films have been prepared by dipping technique and characterized by AFM, XPS, UV-Visible and fluorescence spectroscopy. Optical Absorption properties of the nanocomposite are similar to those of the polymer with an absorption tail in the visible which supports the presence of silver nanoparticles. Despite the lack of fluorescence of the nanoparticles, the composite emits in the yellow green region and the intensity of the fluorescence of the nanocomposite film decreases after the immersion in the culture thus permitting the detection of the fungus by this technique. The fungus can be deposited on films of both the polymer and nanocomposite, nevertheless only in the latter case, an attack on mycelium is observed revealing the fungicidal effect of silver nanoparticles in the nanocomposite.     

NaCl晶体的电子激发分解研究（英文）

通过原位高分辨率透射电子显微镜研究了NaCl晶体的电子激发分解(ESD)过程。实验发现在电子束辐照下,NaCl晶体的不同表面会以相似的分解速率减小。NaCl晶体的外壳层会有许多钠颗粒形成,随着ESD过程的进行,钠颗粒会聚结成大的Na颗粒。在发生电子激发分解的NaCl晶体内部,存在丰富的矩形岛状结构,这种矩形结构的尺寸约为4-7 nm,其中一些拐角发生破缺形成扭结点,同时在NaCl晶体内部也发现了大量位错。研究还发现,碳氢化合物包裹层可以减缓NaCl薄膜的电子激发分解过程。     

Morphology Control and Optical Absorption Properties of Ag Nanoparticles by Ion Implantation

Ion implantation is a powerful method for fabricating nanoparticles in dielectric.For the actual application of nanoparticle composites,a careful control of nanoparticles has to be achieved.In this letter,the size,distribution and morphology of Ag nanoparticles are controlled by controlling the ion current density,ion implantation sequence and ion irradiation dose.Single layer Ag nanoparticles are formed by Ag+ion implantation at current density of 2.5μA/cm2.By Ag and Cu ions sequential implantation,the siz...