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Electron and lattice structure of ultra thin Ag films on Si(111) and Si(001)  [PDF]
V. A. Gasparov,M. Riehl-Chudoba
Physics , 2007, DOI: 10.1016/j.susc.2007.09.020
Abstract: We studied the low temperature (T<130K) growth of Ag on Si(001) and Si(111) flat surfaces prepared by Si homo epitaxy with the aim to achieve thin metallic films. The band structure and morphology of the Ag overlayers have been investigated by means of XPS, UPS, LEED, STM and STS. Surprisingly a (root3xroot3)R30^o LEED structure for Ag films has been observed after deposition of 2-6 ML Ag onto a Si(111)(root3xroot3)R30^o Ag surface at low temperatures. XPS investigations showed that these films are solid, and UPS measurements indicate that they are metallic. However, after closer STM studies we found that these films consists of sharp Ag islands and (root3xroot3)R30^o Ag flat terraces in between. On Si(001) the low-temperature deposition yields an epitaxial growth of Ag on clean Si(001)2x1 with a twinned Ag(111) structure at coverages as low as 10 ML. Furthermore the conductivity of few monolayer Ag films on Si(100) surfaces has been studied as a function of temperature (40-300 K).
Surfactant-like Effect and Dissolution of Ultrathin Fe Films on Ag(001)  [PDF]
S. Terreni,A. Cossaro,G. Gonella,L. Mattera,L. Duo',F. Ciccacci,D. Cvetko,L. Floreano,A. Morgante,A. Verdini,M. Canepa
Physics , 2004, DOI: 10.1103/PhysRevB.70.115420
Abstract: The phase immiscibility and the excellent matching between Ag(001) and Fe(001) unit cells (mismatch 0.8 %) make Fe/Ag growth attractive in the field of low dimensionality magnetic systems. Intermixing could be drastically limited at deposition temperatures as low as 140-150 K. The film structural evolution induced by post-growth annealing presents many interesting aspects involving activated atomic exchange processes and affecting magnetic properties. Previous experiments, of He and low energy ion scattering on films deposited at 150 K, indicated the formation of a segregated Ag layer upon annealing at 550 K. Higher temperatures led to the embedding of Fe into the Ag matrix. In those experiments, information on sub-surface layers was attained by techniques mainly sensitive to the topmost layer. Here, systematic PED measurements, providing chemical selectivity and structural information for a depth of several layers, have been accompanied with a few XRD rod scans, yielding a better sensitivity to the buried interface and to the film long range order. The results of this paper allow a comparison with recent models enlightening the dissolution paths of an ultra thin metal film into a different metal, when both subsurface migration of the deposit and phase separation between substrate and deposit are favoured. The occurrence of a surfactant-like stage, in which a single layer of Ag covers the Fe film is demonstrated for films of 4-6 ML heated at 500-550 K. Evidence of a stage characterized by the formation of two Ag capping layers is also reported. As the annealing temperature was increased beyond 700 K, the surface layers closely resembled the structure of bare Ag(001) with the residual presence of subsurface Fe aggregates.
Synthesis and Characterization of Optically Active Fractal Seed Mediated Silver Nickel Bimetallic Nanoparticles  [PDF]
Joseph Adeyemi Adekoya,Enock Olugbenga Dare,Michael Adediran Mesubi,Neerish Revaprasadu
Journal of Materials , 2014, DOI: 10.1155/2014/184216
Abstract: The synthesis of new seed mediated AgNi allied bimetallic nanocomposites was successfully carried out by the successive reduction of the metal ions in diethylene glycol, ethylene glycol, glycerol, and pentaerythritol solutions, with concomitant precipitation of Ag/Ni bimetal sols. The optical measurement revealed the existence of distinct band edge with surface plasmon resonance (SPR) in the region of 400–425?nm and excitonic emission with maximum peak at 382?nm which were reminiscent of cluster-in-cluster surface enriched bimetallic silver-nickel sols. The morphological characterization by transmission electron microscopy, high resolution transmission electron microscopy, and X-ray diffraction analyses complimented by surface scan using X-ray photoelectron spectroscopy strongly supported the formation of intimately alloyed face-centered silver/nickel nanoclusters. 1. Introduction The synthesis of new materials and the investigation of their characteristic properties is a noble aspect of nanochemistry due to the fact that various applications have been found for these materials in electronics, sensor, optical devices, waveguide, and fibre optics to mention a few. As a result, immense effort directed at synthesizing and manipulating the size, size distribution, and shape of these nanoparticles is inexhaustive. In particular, silver nanoparticles have been largely prepared and evaluated for sensor, optical, and antimicrobial properties. However, the nanocomposite silver nickel is being considered due to its synergistic effect which offers a wide range of applications that include catalysis. Monodispersed allied silver/nickel nanoparticles have been prepared using various chemical routes based on hydrolytic reduction of the metal ions followed by polycondensation of the reduced nuclei. The reactions are largely thermodynamically driven with respect to temperature and time to produce uniformly distributed nanosized particles. There are a number of literature reports on AgNi nanoparticles; Xiao and coworkers presented an approach in which laser ablation was used in the deposition silver/nickel bimetallic nanoparticles; the laser was a pulsed Nd:YAG laser source [1, 2]. The effective nonlinear absorption of Ni/Ag nanoparticles was found to be higher than that of pristine Ag nanoparticles. The nanoparticles were synthesized via wet chemical reduction in C19H42BrN (CTAB) matrix, hydrazine hydrate being the reducing agent, and it was found to be a very potent material for optical limiting and photonic applications in the work of Kishore et al., 2012 [3].
Facile Synthesis of Porous-Structured Nickel Oxide Thin Film by Pulsed Laser Deposition  [PDF]
Siamak Pilban Jahromi,Nay Ming Huang,Ahmad Kamalianfar,Hong Ngee Lim,Muhamad Rasat Muhamad,Ramin Yousefi
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/173825
Abstract: Porous-structured nickel oxide (PsNiO) was obtained through the oxidization of a nickel thin film. The nickel thin film was deposited using the pulsed laser deposition (PLD) method on a nickel foil as a substrate. The results show uniform PsNiO after the oxidization of the nickel thin film at 750°C for 1?h. X-ray diffraction (XRD) indicates formation of the NiO crystalline structure. Field emission scanning electron microscopy (FESEM) reveals different morphology on the surface of the nickel foil (sample A) and on the nickel thin film (sample B). Comparison of the FESEM results after oxidization shows that the PsNiO on the nickel thin film was more regular and controllable than the NiO layer on the nickel foil. The FESEM images also show that the thickness of the nickel thin film affected the PsNiO size obtained after oxidization. This resulted from the growth of the porous structure at grain boundaries and from the grain sizes. The electrochemical properties of the PsNiO as an electrode are investigated by cyclic voltammetry (CV). These results show the effect of PsNiO size on the current of anodic peak. 1. Introduction Porous-structured nickel oxide (PsNiO) thin films have numerous applications in a variety of fields,such as electrochemical properties which include charging/discharging mechanism and long life cycles [1], electrochromic display devices [2], gas sensors [3], lithium-ion batteries [4], and catalysts [5]. The porous structure thin film provides a specific surface area and can facilitate a very short diffusion pathway for ions. The control of the surface morphology of the NiO thin film has attracted considerable interest for the development of advanced materials. The large variety of applications for NiO thin films results from its morphology. The PsNiO thin film has been fabricated using several physical and chemical techniques, such as chemical bath deposition [2], sol-gel process [6], anodic electrochemical deposition [7], hydrothermal method [8], thermal decomposition [9], and pulse laser deposition method (PLD) [10]. Uniform morphology, film thickness, and purity, as well as controllable pore size improve the electrochemical properties of the NiO thin film. Pulse laser deposition (PLD) is a one method used to fabricate high-quality thin films that is advantageous in tuning the film characteristics [10]. However, there are a few reports on the fabrication of NiO thin film arrays using PLD [11–13]. In contrast, there is a wide range of investigations on high/low temperature oxidization of pure nickel. The two most common methods used to
Surface phonons of NiO(001) ultrathin films grown pseudomorphically on Ag(001)  [PDF]
K. L. Kostov,S. Polzin,F. O. Schumann,W. Widdra
Physics , 2015,
Abstract: For a ultrathin NiO(001) film of 4 monolayers (ML) thickness grown on Ag(001), the vibrational properties have been determined by high-resolution electron energy loss spectroscopy (HREELS). For the well-ordered pseudomorphically grown film, nine phonon modes have been identified and their dispersions have been revealed along the Gamma-X high-symmetry direction. The comparison with phonon data for a 25 ML thick NiO(001) film shows that the NiO (001) phonon properties are already fully developed at 4 ML. Significant differences are found for the surface-localized phonon S6 which has an increased dispersion for the ultrathin film. The dipole-active Fuchs-Kliewer phonon-polariton exhibits a narrower lineshape than the mode found for a single-crystal surface, which might hint to a reduced antiferromagnetic coupling in the ultrathin film.
Pulsed Laser Deposited Nickel Doped Zinc Oxide Thin Films: Structural and Optical Investigations  [PDF]
Journal of Nano- and Electronic Physics , 2013,
Abstract: Structural and optical studies has been done on Nickel doped Zinc Oxide (NixZn1 – xO, x 0.03, 0.05 and 0.07 by weight) thin films prepared by pulsed laser deposition technique. The films are characterized by X-ray diffraction, Uv-vis spectroscopy, X-ray photoelectron spectroscopy. We observed a slight red shift in the optical band gap in the NiZnO subsequent to Ni doping. This shift can be assigned due to the sp-d exchange interaction of Ni- d states with s and p-states of ZnO. Also X-ray photoelectron spectroscopy studies show that Ni has well substituted in + 2 oxidation state by replacing Zn2+.
(001)-oriented FePt/Ag composite films for perpendicular recording

Wenfeng LIU,Fang WANG,Xiaohong XU,

金属学报(英文版) , 2009,
Abstract: FePt/Ag thin films were deposited by magnetron sputtering onto 7059 glass substrates, then were annealed at 550 ℃ for 30 min. Nanostructured FePt/Ag films were successfully obtained with the magnetic easy axis of Ll_0 FePt perpendicular to the film plane. It was found that the development of (001) texture depended strongly on the thicknesses of FePt magnetic layer and Ag underlayer. The L10 ordered FePt(15 nm)/Ag(50 nm) with (001) orientation can be obtained. And the perpendicular coercivity of FePt(15 nm)/Ag(50 nm) film reached to 7.2×10~5 A/m, whereas the longitudinal one was only 3.2×10~4 A/m. The non-magnetic Ag underlayer can not only induce (001) orientation and ordering of FePt grains, but also reduce the intergrain interactions.
Epitaxy of Fe3O4 on Si(001) by pulsed laser deposition using a TiN/MgO buffer layer  [PDF]
D. Reisinger,M. Schonecke,T. Brenninger,M. Opel,A. Erb,L. Alff,R. Gross
Physics , 2003, DOI: 10.1063/1.1587885
Abstract: Epitaxy of oxide materials on silicon (Si) substrates is of great interest for future functional devices using the large variety of physical properties of the oxides as ferroelectricity, ferromagnetism, or superconductivity. Recently, materials with high spin polarization of the charge carriers have become interesting for semiconductor-oxide hybrid devices in spin electronics. Here, we report on pulsed laser deposition of magnetite (Fe3O4) on Si(001) substrates cleaned by an in situ laser beam high temperature treatment. After depositing a double buffer layer of titanium nitride (TiN) and magnesium oxide (MgO), a high quality epitaxial magnetite layer can be grown as verified by RHEED intensity oscillations and high resolution x-ray diffraction.
Preparation and magnetoresistance of Ag 2+x Se thin films deposited via Pulsed Laser Deposition  [PDF]
B. Mogwitz,C. Korte,M. von Kreutzbruck,L. Kienle,J. Janek
Physics , 2007, DOI: 10.1063/1.2433128
Abstract: The preparation of Ag 2+x Se thin films with thicknesses between 4 nm and 3000 nm by pulsed laser deposition on single crystalline NaCl and MgO substrates is reported. The films are perfectly dense and show a good lateral uniformity with a small number of defects. The microstructure of the films corresponds to a nanoparquet, being composed of two different phases of silver selenide. One phase is identified as the Naumannite low temperature phase of silver selenide, the structure of the other phase has not been reported in detail before and probably represents a metastable phase. Silver-rich films contain silver precipitates with typical sizes on the nanoscale. Their presence and their size appears to be responsible for the large and linear magnetoresistance effect of silver-rich silver selenide.
Ab-initio density functional study of O on the Ag(001) surface  [PDF]
M. Gajdos,A. Eichler,J. Hafner
Physics , 2003, DOI: 10.1016/S0039-6028(03)00514-4
Abstract: The adsorption of oxygen on the Ag(001) is investigated by means of density functional techniques. Starting from a characterization of the clean silver surfaces oxygen adsorption in several modifications (molecularly, on-surface, sub-surface, Ag$_2$O) for varying coverage was studied. Besides structural parameters and adsorption energies also work-function changes, vibrational frequencies and core level energies were calculated for a better characterization of the adsorption structures and an easier comparison to the rich experimental data.
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