Hillock formation by surface diffusion on thin silver films

The kinetics of hillock formation on silver films annealed in oxygen have been observed by recording the point of substantial completion of their growth. The effects of temperature and film thickness are accounted for in a quantitative model which describes hillock growth as proceeding by surface diffusion to reduce compressive stresses caused by differential thermal expansion between film and substrate. The effects of oxygen atmospheres are accounted for in terms of the energetics of hillock nucleation, and the mechanism of surface diffusion in oxygen is discussed.     

Local modification of thin oxide films on a titanium surface

It is shown that a controllable structural rearrangement of a thin titanium oxide film, accompanied by a change in the bandgap width, can be accomplished under the probe tip of a scanning tunneling microscope (STM). The mechanism of the rearrangement is considered to be the migration of cations and oxygen vacancies in the electric field of the STM.     

Coupling of surface plasma oscillations in thin periodically corrugated silver films

We investigated surface plasma oscillations (SPO's) in a layer system of thin dielectric films with a periodically corrugated surface coated by a silver film. SPO's at both surfaces of the silver film could be excited by light. We observed coupling of the two SPO's through the thin film via the periodicity of the surface and as a consequence a discontinuity in the dispersion relations of the SPO.     

Magnetoconductivity of thin epitaxial silver films

The magnetoconductance (MC) of thin epitaxial Ag films on Si(111) surfaces is studied as a function of film thickness (1–125 monolayers (ML)) at 20 K under ultra high vacuum (UHV) conditions. Three different regimes of magnetoconductance are observed depending on the degree of disorder in the films which is controlled by film thickness and annealing procedures. Thick films (d>3 ML) with diffuse electron transport show in the case of large elastic scattering times ₀ a classical, negative MC B ² and in the case of small ₀ a positive MC due to weak localization effects. The MC of thin films (d<2 ML) which have a conductance smaller than e ²/h, i.e. localized electron states, is negative again.     

Light scattering study of surface plasmon resonances in very thin silver films

The surface plasmon modes of Ag thin films were studied by the light scattering method in the thickness range down to 100 Å. The observed thickness dependence of the resonance peaks was analysed in detail by the theory of Kretschmann. It is shown that the coupled surface plasmon modes in the very thin films can be detected only in modified forms by the light scattering experiment.     

稀土镧对薄膜中银纳米粒子的细化作用

通过更换基底材料,证实了稀土镧对AgBaO薄膜中银纳米粒子的细化作用.用LewisCampbell的薄膜理论分析表明,稀土镧对银纳米粒子的细化作用机理是,基底吸附稀土镧增强了基底对银原子的等效吸附能和基底表面徙动激活能,使镧和银结合形成的复合小银粒子在基底表面的徙动扩散运动受到削弱,进而减少了相互团聚所致.基底表面徙动激活能增量在0.04—0.07eV之间,相应的基底对银原子的等效吸附能增量在0.08—0.42eV之间 关键词： 细化 稀土 纳米粒子 粒度     

Deposition of hexagonal boron nitride thin films on silver nanoparticle substrates and surface enhanced infrared absorption

Silver nanoparticle thin films with different average particle diameters are grown on silicon substrates. Boron nitride thin films are then deposited on the silver nanoparticle interlayers by radio frequency （RF） magnetron sputtering. The boron nitride thin films are characterized by Fourier transform infrared spectra. The average particle diameters of silver nanoparticle thin films are 126.6, 78.4, and 178.8 nm. The results show that the sizes of the silver nanoparticles have effects on the intensities of infrared spectra of boron nitride thin films. An enhanced infrared absorption is detected for boron nitride thin film grown on silver nanoparticle thin film. This result is helpful to study the growth mechanism of boron nitride thin film.     

Electron energy losses from thin silver films

A simple dielectric theory of electron energy losses in a thin metal overlayer is extended to include multiple losses. This theory is then compared with recent experimental data by Backes and Ibach. These comparisons reveal several inadequacies in the basic model, especially with regard to the shape and parameter dependence of the quasi-elastic peak.     

Enhanced photoluminescence of conjugated polymer thin films on nanostructured silver

Photoluminescence of a conjugated polymer in the presence of surface plasmons on metallic nanoparticles is studied. A layered device structure was constructed that enabled control over nanoparticle diameter and separation between the polymer and nanoparticles layers. The dependence of the surface plasmon evanescent field and energy transfer has been investigated with the largest enhancement in photoluminescence observed at a 40 nm distance separation between the fluorophore and the surface plasmon. A spectrum of surface plasmon resonances ranging from the emission to the absorption energies of the conjugated polymer revealed largest enhancements when the resonance was tuned to the conjugated polymer emission energy. At peak photoluminescence the maximum photoluminescent enhancement was found to be 5.6 times of the photoluminescence of the control structure and the total integrated enhancement was 5.9 times.     

Asymmetric distribution of surface second harmonic generation for thin silver films deposited on Si(111)

The asymmetric distributions of surface optical second harmonic generation (SHG) through azimuthally angular scans of (111) silicon wafers on which thin silver films were deposited, have been detected with different polarizations of output beams. On account of the inversion symmetry of silicon crystals, the SHG for the Ag/Si system is mainly contributed by the silver film and the silicon surface. In this work, we found that the interface strain implies an asymmetric intensity variation of SHG with respect to the surface azimuthal angles as an ultra thin Ag film is deposited on silicon wafers. This asymmetric behavior is prominent as the deposited silver layer is heated so that the continuous film aggregates to become granular nanoparticles. Similar changes of the surface asymmetric SHG are observed for a bare Si wafer imposed upon by an external force.     

The nucleation,growth, structure and epitaxy of thin surface films

A review is given of the evidence available on the mechanism of growth and the structure of thin deposited films. The main attention is devoted to the growth of metals onto single crystal substrates, particularly those formed by the evaporation technique. Some consideration of other types of deposit is also given, including chemically formed films and epitaxial silicon layers. A survey of the various experimental techniques which can be used for structural studies on thin films is given, but the main evidence presented is based upon electron diffraction and transmission electron microscopy.

The mode of nucleation of the layers is described, and the evidence for the way in which the nuclei develop into a continuous deposit film is outlined. This includes the evidence obtained from growing films inside the electron microscope, which reveals two important processes. These are the ‘liquid-like’ coalescence of nuclei and islands, and recrystallization of islands.

The various imperfection structures observed in thin films are described, and an attempt is made to explain the mechanisms by which these imperfections are formed during the growth of the film.

Finally, the significance of the experimental evidence on growth and structure is discussed in relation to the occurrence of epitaxy, and an attempt is made to determine the most important directions for future studies of epitaxy.     

Simultaneous imaging for surface and internal structure of polymer blend thin films

A novel experimental technique for three-dimensional (3D) visualization of phase-separated structure of polymer blend thin film was proposed. Polystyrene/poly(methyl methacrylate) (PS/PMMA) blend thin films with the thickness of approximately 100 nm were cut at extremely low angle by utilizing surface and interface cutting analysis system (SAICAS), and the cross-section was exposed as gradient surface with the width of approximately 2.5 μm. SFM investigation for the grazing cross-section imaged the detailed internal and surface phase separated structure of the (PS/PMMA) blend thin films on one image.     

On the localization of electron states near silver ion adsorbed on atomic-rough surface of AgCl nanocrystal

Local partial and total densities of states for AgCl nanocrystals with the adsorbed silver ion were calculated by semi-empirical tight-binding method relying on a self-consistent approach for the effective charges and dipole moments of the ions. Adsorption was considered as on the atomically-rough surface (near the step and step fracture) as on the smooth surface. Visualization of the wave functions was performed for the localized states. Basing on the obtained data a conclusion is specifically made that one can expect an enhancement of photoelectron localization with a decrease of the anions number in the substrate nearest to the adsorbed ion. It means that the most efficient trapping of photoelectron should occur under adsorption on a smooth surface rather than near the steps and their fractures as it was assumed previously.     

Formation of silver thin films and nanoparticles inside and on the surface of silver-containing glasses by electron irradiation

It is shown experimentally that irradiation of silver-ion-containing glasses by 5–7-keV electrons with doses of 20–50 mC/cm² results in the formation of a silver thin film and nanoparticles on the surface. If the concentration of silver ions in the glass is high, a subsurface film arises as well. These effects are due to a negative space charge region forming under the surface. As a result, silver ions migrate in the resulting field from the volume of the glass toward the negative space charge region and the surface and thermalized electrons reduce the ions to neutral atoms.     

Optical properties of composite thin films containing silver nanoparticles

Absorption and reflection of electromagnetic radiation by a composite thin film consisting of a transparent dielectric matrix with inclusions of metal nanoparticles of radius much less than the wavelength were theoretically investigated based on the Maxwell–Garnett model. The absorption, reflection, and transmission of optical radiation in such a dielectric composite film were analyzed using effective optical parameters for the refractive index and absorption coefficient that depended on the nanoparticle size.     

Secondary electron emission from thin self-supporting films of silver

The paper deals with the measurement of secondary electron emission and the scattering of primary electrons on thin self-supporting films of Ag. The measured values of the practical range agree with the older results obtained by Kanter. New results are those concerning the maximum depth from which the primaries are scattered back to the front surface and the maximum range of secondaries, which has been found to be about 300 å.     

Influence of surface properties on the structure of granular silver films and excitation of localized plasmons

Granular silver films deposited on a thin insulating film of amorphous hydrogenated carbon (a-C:H) and transparent conducting electrode (polycrystalline indium tin oxide (ITO) layer) have been investigated by spectroscopy and microscopy methods. The extinction spectra of silver films on the surface of these materials are found to be significantly different. An annealing of silver films causes a blue shift of the peak of plasmon resonance band in the spectrum of silver nanoparticles: by 16 nm on the a-C:H surface and by 94 nm on the ITO surface. Silver films on the surface of a-C:H films are characterized by a narrower band in the extinction spectrum, which is peaked at 446 nm. The changes observed in the optical density of Ag films are related to the change in size and area of nanoparticles. The results of spectral studies of Ag films are in agreement with the data on the nanostructure obtained by scanning electron microscopy and statistical image processing. The spectra of granular silver films are shown to correlate well with the nanoparticle distribution function over the film area.     

Laser-induced patterning of silver thin films using interference effects

Submicron patterning of the spatial arrangement of spherical silver nanoparticles on a substrate is reported. The patterned samples were obtained by irradiating a thin silver film in the quasipercolated state with short laser pulses. Light reached the sample through a slit on a highly reflecting silicon mask placed parallel to the surface of the sample and was reflected between the sample and the inner face of the mask. The incident and reflected light interfered on the sample’s surface creating a complicated pattern of thin lines along which spherical-shaped silver nano-particles are concentrated. We provide a simple model to explain the observed patterns and briefly discuss how could one control the shape and thickness of the patterned lines of nanoparticles.