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1.
G. Çelik Ş. Ateş 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):433-437
In this contribution we present scanning tunnelling microscopy (STM) and spectroscopy (STS) investigations on isolated cobalt
clusters in contact with Ge(001). Mass-filtered nanoparticles with diameters ranging from 3 to 11 nm are generated using an
arc cluster ion source (ACIS) and deposited under soft landing conditions (Ekin/atom < 0.5 eV). Since the tip radius is of the same order as the nanoparticle diameters the recorded STM images are significantly
affected by tip folding.
By means of the “blind reconstruction method" it is possible to approximate the tip shape. After a respective deconvolution
of the image structural features of the particle facets become observable. According to the equilibrium shape of the clusters
being a truncated octahedron in the size range under investigation, hexagonal and rectangular features appear in the images.
STS is sensitive to occupied and unoccupied states near the Fermi level and reveals the existence of distinct states in the
tunnelling conductivity of the substrate as well as on the clusters. The richly structured density of states of the germanium
surface serves here as tip condition test. First measurements of the tunnelling conductivity of the CoN/Ge(001) are presented and discussed. 相似文献
2.
Wetting characteristics of micro-nanorough substrates of aluminum and smooth silicon substrates have been studied and compared by depositing hydrocarbon and fluorinated-hydrocarbon coatings via plasma enhanced chemical vapor deposition (PECVD) technique using a mixture of Ar, CH4 and C2F6 gases. The water contact angles on the hydrocarbon and fluorinated-hydrocarbon coatings deposited on silicon substrates were found to be 72° and 105°, respectively. However, the micro-nanorough aluminum substrates demonstrated superhydrophobic properties upon coatings with fluorinated-hydrocarbon providing a water contact angle of ∼165° and contact angle hysteresis below 2° with water drops rolling off from those surfaces while the same substrates showed contact angle of 135° with water drops sticking on those surfaces. The superhydrophobic properties is due to the high fluorine content in the fluorinated-hydrocarbon coatings of ∼36 at.%, as investigated by X-ray photoelectron spectroscopy (XPS), by lowering the surface energy of the micro-nanorough aluminum substrates. 相似文献
3.
In this work, we have studied thermal stability of nanoscale Ag metallization and its contact with CoSi2 in heat-treated Ag(50 nm)/W(10 nm)/Co(10 nm)/Si(1 0 0) multilayer fabricated by sputtering method. To evaluate thermal stability of the systems, heat-treatment was performed from 300 to 900 °C in an N2 ambient for 30 min. All the samples were analyzed by four-point-probe sheet resistance measurement (Rs), Rutherford backscattering spectrometry (RBS), X-ray diffractometry (XRD), and atomic force microscopy (AFM). Based on our data analysis, no interdiffiusion, phase formation, and Rs variation was observed up to 500 °C in which the Ag layer showed a (1 1 1) preferred crystallographic orientation with a smooth surface and Rs of about 1 Ω/□. At 600 °C, a sharp increase of Rs value was occurred due to initiation of surface agglomeration, WSi2 formation, and interdiffusion between the layers. Using XRD spectra, CoSi2 formed at the Co/Si interface preventing W silicide formation at 750 and 800 °C. Meantime, RBS analysis showed that in this temperature range, the W acts as a cap layer, so that we have obtained a W encapsulated Ag/CoSi2 contact with a smooth surface. At 900 °C, the CoSi2 layer decomposed and the layers totally mixed. Therefore, we have shown that in Ag/W/Co/Si(1 0 0) multilayer, the Ag nano-layer is thermally stable up to 500 °C, and formation of W-capped Ag/CoSi2 contact with Rs of 2 Ω/□ has been occurred at 750-800 °C. 相似文献
4.
S. Duffe T. Irawan M. Bieletzki T. Richter B. Sieben C. Yin B. von Issendorff M. Moseler H. Hövel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):401-408
The low energy deposition of silver cluster cations with
561 (±5) atoms on a cold fullerene covered gold surface has
been studied both by scanning tunneling microscopy and molecular
dynamics simulation. The special properties of the
C60/Au(111) surface result in a noticeable fixation of the
clusters without a significant change of the cluster shape. Upon
heating to room temperature we observe a flattening or shrinking
of the cluster samples due to thermal activation. Similar changes were observed also for mass selected Ag clusters with other
sizes. For comparison
we also studied Ag islands of similar size, grown by low
temperature deposition of Ag atoms and subsequent annealing. A
completely different behavior is observed with much broader size
distributions and a qualitatively different response to
annealing. 相似文献
5.
Thermal stability of Ag layer on Ti coated Si substrate for different thicknesses of the Ag layer have been studied. To do this, after sputter-deposition of a 10 nm Ti buffer layer on the Si(1 0 0) substrate, an Ag layer with different thicknesses (150-5 nm) was sputtered on the buffer layer. Post annealing process of the samples was performed in an N2 ambient at a flow rate of 200 ml/min in a temperature range from 500 to 700 °C for 30 min. The electrical property of the heat-treated multilayer with the different thicknesses of Ag layer was examined by four-point-probe sheet resistance measurement at the room temperature. Phase formation and crystallographic orientation of the silver layers were studied by θ-2θ X-ray diffraction analysis. The surface topography and morphology of the heat-treated films were determined by atomic force microscopy, and also, scanning electron microscopy. Four-point- probe electrical measurement showed no considerable variation of sheet resistance by reducing the thickness of the annealed Ag films down to 25 nm. Surface roughness of the Ag films with (1 1 1) preferred crystallographic orientation was much smaller than the film thickness, which is a necessary condition for nanometric contact layers. Therefore, we have shown that the Ag layers with suitable nano-thicknesses sputtered on 10 nm Ti buffer layer were thermally stable up to 700 °C. 相似文献
6.
We investigate the morphology of a pentacene (C22H14) film adsorbed on the Cu(1 1 9) vicinal surface by scanning tunnelling microscopy (STM). Thermal treatment of a thick film of molecules generates a long-range ordered structure. Series of molecular rows are alternated with areas where the molecules assume two equivalent orientations. STM data analysis suggests that the ordered structure can be described by a rippled morphology. The behaviour of the film at different annealing temperatures suggests a possible explanation of the film structure as due to an adsorbate-induced modification of the substrate. 相似文献
7.
M. Ziese R. Höhne H.C. Semmelhack H. Reckentin N.H. Hong P. Esquinazi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(4):415-422
The magnetotransport properties of magnetite films with different microstructures were investigated in order to identify prerequisites
for the attainment of a large tunnelling magnetoresistance in polycrystalline samples. Epitaxial films on MgAl2O4, polycrystalline films on Al2O3 and rough MgAl2O4 substrates and a polycrystalline La0.7Ca0.3MnO3 film on MgO were compared. Although grain boundaries induce a large high-field magnetoresistance in magnetite films, the
low-field magnetoresistance characteristic for spin-polarized tunnelling was virtually absent in these samples. Two factors
might be responsible for this behaviour: (1) grain boundaries in magnetite are conducting and do not form tunnelling barriers
and (2) the spin-polarization near grain boundaries is suppressed due to non-stoichiometry.
Received 15 April 2002 Published online 13 August 2002 相似文献
8.
The electrostatic potential mapped on the electron density contour of gas phase molecules is used to identify several molecules physisorbed on transition metals imaged by scanning tunnelling microscopy within the molecular HOMO-LUMO gap. It is rationalized that the inverted of this potential, representing the potential energy felt by a negative test charge, is a good concept to interpret changes in the dielectricity constant through the influence of physisorbed molecules and thus to understand their submolecular resolution images. The validity of the concept is demonstrated on dichlorobenzene, chloronitrobenzene, and two azobenzene derivates on the surfaces of Au(111), Ag(111), and Cu(111). 相似文献
9.
The adsorption of L-alanine on Cu(111) surface is studied by means of scanning tunnelling microscopy under ultra-high vacuum conditions. The results show that the adsorbates are chemisorbed on the surface, and can form a two-dimensional gas phase, chain phase and solid phase, depending on deposition rate and amount. The adsorbed molecules can be imaged as individual protrusions and parallel chains in gas and chain phases respectively. It is also found that alanine can form (2 × 2) superstructure on Cu(111) and copper step facet to (110) directions in solid phase. On the basis of our scanning tunnelling microscopic images, a model is proposed for the Cu(111)(2 ×2)-alanine superstructure. In the model, we point out the close link between (110)-direction hydrogen bond chains with the same direction copper step faceting. 相似文献
10.
Fumio Kokai Naoki Tachi Keita Kobayashi Akira Koshio 《Applied Surface Science》2009,255(24):9622-9625
Three types of single-wall carbon nanohorn (SWNH) aggregates hybridized with carbon nanocapsules (CNCs) containing Fe3C, Co, or Ag were produced by laser vaporization of graphite mixed with Fe, Co, or Ag in Ar gas. Characterization by transmission electron microscopy revealed that although the three hybrid structures had different diameter distributions with average diameters of 96, 90, and 85 nm, respectively, their SWNH layers had similar thicknesses (17-18 nm on average). The diameter difference is explained by the sizes (16-24 nm on average) of the encapsulated CNCs, the formation of which depended on the carbon solubility of the three metals and the precipitation of the graphitic layers. In addition, there was a stronger correlation between the diameters of the hybrids and the thicknesses of the SWNH layers for the three types. We suggest that the formation mechanism of the three structures is based on the assembly of SWNHs around a molten metal-carbon particle with certain ranges of lengths and diameters, respectively. 相似文献
11.
H. Nabika S. Deki 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):369-372
The effect of colloidal dispersion of silver on the
luminescent properties of Eu (III) complex with
pyridine-3,5-dicarboxylic acid (PyDC) was investigated. The
luminescence from Förster type europium complex was enhanced
several times with the presence of Ag colloid and the
enhancement factor showed Ag concentration dependence. The
observed enhancement effect was discussed in view of
surface-enhancement effect and optical absorption due to surface
plasmon resonance, both arising from excitation of surface
plasmon polariton. The coordination structure around Eu (III)
ion was also affected with the presence of Ag colloid, which
induced the change in the intensity ratio between two emission
bands of
5
D
0
7
F
1
and
5
D
0
7
F
2
transitions of Eu (III) ion. 相似文献
12.
The silver nanoparticles with about 10 nm diameter were immobilized onto the halloysite nanotubes (HNTs) via the in situ reduction of AgNO3 by polyol process. The silver nanoparticles supported halloysite nanotubes (Ag/HNTs), with Ag content of about 11%, were used for the catalyzed reduction of 4-nitrophenol (4-NP) with NaBH4 in alkaline aqueous solutions. The effect of the reduction of 4-NP catalyzed by the catalysts in the presence of variable concentration NaBH4 was investigated. It was found that the reduction rate increased with the increasing of the amounts of NaBH4. And the larger amounts of NaBH4 reduced the induction time. 相似文献
13.
Tino Roll Marion Meier Sevilay Akcöltekin Miriam Klusmann Henning Lebius Marika Schleberger 《固体物理学:研究快报》2008,2(5):209-211
CaF2(111) single crystal surfaces have been irradiated with fast heavy ions under oblique angles resulting in chains of nanosized hillocks. In order to characterize these nanodots with respect to their conductivity we have applied non‐contact atomic force microscopy using a magnetic tip. Measurements in ultra high vacuum as well as under ambient conditions reveal a clearly enhanced electromagnetic interaction between the magnetic tip and the nanodots. The dissipated energy per cycle is comparable to the value found for metals, indicating that the interaction of the ion with the target material leads to the creation of metallic Ca nanodots on the surface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
We report the superior stability of the composite Cs2CO3 :Ag/Ag cathode structure, which can be used in efficient organic light-emitting diodes (OLEDs). Devices with the Cs2CO3:Ag (1:10, 5nm)/Ag (95nm) cathode show a considerably improved lifetime compared with the control device with the Cs2CO3 (0.5 nm)/Ag (100 nm) cathode. The composite Cs2CO3 :Ag/Ag film is proved to be stable in the atmosphere. X-ray diffraction (XRD) is applied to analyze the crystalline structure of the Cs2CO3:Ag film, and it is demonstrated that CsAg alloy is formed, leading to the improved stability of the thin film and the devices. 相似文献
15.
N. Nishi J. Nishijo K. Judai C. Okabe O. Oishi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):287-290
UV photoexcitation of (t-butylethynyl copper)24
cluster films induces segregation of the crystals into metallic and organic
phases and leads to evolve the metallic sheets sandwiched by organic
polymers. The growth of the metallic crystals in the plane of the
photo-electromagnetic field is attributed due to plasmon-plasmon interaction
among nanoparticles embedded in dielectric polymer matrices. The surface
enhanced photochemical reaction of residual cluster molecules on the photon
incident direction is expected to take an important role for joining the
metal particles to produce a metallic sheet. We can apply this phenomenon
for photolithographic copper pattern generation on a flexible base plate. 相似文献
16.
We investigated the effect of surface property of polyimide substrate on the formation of pentacene thin-film by using atomic force microscopy (AFM) and X-ray reflectivity (XRR) and diffuse scattering (XDS). Two types of polymer films were prepared: (1) polyimide (PAA-PI) from poly(amic acid) (PAA) (2) polyimide hybrid (PAA-PI-H) prepared by hybridizing the PAA and soluble polyimide (PI) with a octadecyl side chain. The hybridization ratio of PI to PAA was 2/98 in wt%. The water contact angle for PAA-PI-H and PAA-PI were around 80° and 64°, respectively. Morphology of pentacene with a ropelike structure and (1 1 0) peak around 1.4 Å in qz was found when it was deposited on PAA-PI thin-film. Different pentacene morphology was observed when it was deposited on PAA-PI-H thin-film. The different morphology might be due to a 5-6 nm thick additional layer (∼0.95 ρfilm) at the interface between pentacene and PAA-PI-H thin-film caused by a long alkyl side chain introduced to the polymer main chain. 相似文献
17.
The Au(1 0 0) surface structure in contact with 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) has been observed using electrochemical atomic force microscopy (EC-AFM) under an electrochemically controlled potential. The AFM images, taken in EMImBF4 in the potential range from −0.6 to 0.2 V vs. Ag/Ag(I), shows a fourfold symmetry with the distance between protrusions of ≈0.30-0.32 nm. This structure agrees well with the ideal surface structure of Au(1 0 0)-(1 × 1) and it is very similar to that previously obtained in a sulfuric acid aqueous solution. 相似文献
18.
The adsorption of germanium on Ag(1 1 0) has been investigated by scanning tunnelling microscopy (STM), as well as surface X-ray diffraction (SXRD). At 0.5 germanium monolayer (ML) coverage, Low Energy Electron Diffraction (LEED) patterns reveals a sharp c(4 × 2) superstructure. Based on STM images and SXRD measurements, we present an atomic model of the surface structure with Ge atoms forming tetramer nano-clusters perfectly assembled in a two-dimensional array over the silver top layer. The adsorption of the germanium atoms induces a weak perturbation of the Ag surface. Upon comparison with results obtained on the (1 1 1) and (1 0 0) faces, we stress the role played by the relative interactions between silver and germanium on the observed surface structures. 相似文献
19.
Growth of Cu Films on Si(111)-7×7 Surfaces at Low Temperature: A Scanning Tunnelling Microscopy Study
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SHEN Quan-Tong SUN Guo-Feng LI Wen-Juan DONG Guo-Cai HAN Tie-Zhu MA Da-Yan SUN Yu-Jie JIA Jin-Feng XUE Qi-Kun 《中国物理快报》2007,24(11):3214-3217
Morphologies of Cu(111) films on Si(111)-7×7 surfaces prepared at lowtemperature are investigated by scanning tunnelling microscopy (STM) andreflection high-energy electron diffraction (RHEED). At the initial growth stage, Cu films are flat due to the formation of silicide at the interface that decreases the mismatch between Cu films and the Si substrate. Different from the usual multilayer growth of Cu/Cu(111), on the silicide layer a layer-by-layer growth is observed. The two dimensional (2D) growth is explained by the enhanced high island density at low deposition temperature. Increasing deposition rateproduces films with different morphologies, which is the result of Ostwald ripening. 相似文献
20.
We report on a two-step method for oxidation of Pb(111) surfaces, which consists of low temperature (90K) adsorption of 02 and subsequent annealing to room temperature. In situ scanning tunnelling microscopy observation reveals that oxidation of Pb(111) can occur effectively by this method, while direct room temperature adsorption results in no oxidation. Temperature-dependent adsorption behaviour suggests the existence of a precursor state for 02 adsorption on Pb(111) surfaces and can explain the oxidation-resistance of clean Pb(111) surface at room temperature. 相似文献