Ag Au Film Research Articles

Thickness measurement of bimetallic film using surface plasmon resonance holographic microscopy.

Bimetallic film with high stability and sensitivity is often used to excite surface plasmon resonance (SPR). The thicknesses of the bimetallic film play an important role in quantitative retrieval of the sample's parameters, and a precise measurement method is not available until now. In this paper, we propose a method for measuring the thicknesses of bimetallic film using surface plasmon resonance holographic microscopy (SPRHM). Considering that the refractive index of the dielectric upon the bimetallic film sensitively modulates the SPR phase response, the two thickness parameters of bimetallic film can be calculated by two phase-contrast SPR images with two different liquid dielectrics. The capability of this method was verified with several Ag-Au film couples by using a compact SPRHM setup. Our work provides a precise characterization method for the parameters of SPR configuration and may find wide applications in the research fields of SPR sensing and imaging.

Structural and scattering characteristics model of a fractal nanoclustered island Ag-Au films

Samples of Ag/Au nanocluster/island fractal nanofilms obtained by thermal diffusion deposition from a colloidal solution are presented. Modeling and evaluation of the features of their structure in the approximation of diffusion-limited aggregation are carried out. The evaluation of the scattering characteristics of the study on the model samples in the framework of the Fischer-Burford relation is made.

Nanosecond laser ablation of Ag–Au films in water for fabrication of nanostructures with tunable optical properties

In this study, we present results on nanosecond laser ablation of Ag–Au bimetallic thin films in double-distilled water. A standard on-axis pulsed laser deposition technology is used for the thin-film deposition. The targets used in the deposition stage were composed of two sections, each containing Au or Ag. Varying the area of the sections of the target, thin bimetallic films with different ratio of Ag:Au (72:28, 56:44, 50:50, and 34:66) were obtained. As-deposited thin films were immersed in double-distilled water and undergo irradiation with nanosecond laser pulses. The optical absorption spectra of the obtained bimetallic colloids show a single-surface plasmon resonance (SPR) band, positioned between SPR bands of the monometallic Ag and Au nanoparticles (NPs), proving the formation of Ag–Au alloyed NPs. A linear dependence of the SPR maximum of the resulting colloidal NPs on the metal concentration of the deposited thin films was established. The influence of the laser wavelength (the four harmonics of Nd:YAG laser), laser fluence and film thickness on the morphology, particle-size distribution, and optical properties of the obtained colloidal Ag–Au NPs was also studied. TEM analyses of the dried drops of the colloids reveal mainly two types of shapes of the produced nanostructures depending on the processing conditions: spherical NPs and network of nanowires. A characteristics size of the formed nanostructures of about a few nanometers was estimated in the cases of ablation at all the wavelengths used. However, a broader size distribution and presence of larger amount of bigger particles (diameters up to 50 nm) were observed in the case of ablation at 1064 nm. The laser fluence and film thickness are also found to influence the nanostructure size and morphology. The proposed technique can be a basis for the fabrication of complex nanostructure colloids with application in biophotonics, sensor design, and catalysis.

Structure formation in Ag-X (X = Au, Cu) alloys synthesized far-from-equilibrium

We employ sub-monolayer, pulsed Ag and Au vapor fluxes, along with deterministic growth simulations, and nanoscale probes to study structure formation in miscible Ag-Au films synthesized under far-from-equilibrium conditions. Our results show that nanoscale atomic arrangement is primarily determined by roughness build up at the film growth front, whereby larger roughness leads to increased intermixing between Ag and Au. These findings suggest a different structure formation pathway as compared to the immiscible Ag-Cu system for which the present study, in combination with previously published data, reveals that no significant roughness is developed, and the local atomic structure is predominantly determined by the tendency of Ag and Cu to phase-separate.

Durability of Ultra-Thin Silver Films and Silver—Gold Alloy Films under UV Irradiation**Supported by the National Natural Science Foundation of China under Grant No 61308070.

Silver films (Ag) and silver—gold films (Ag—Au) with thickness ∼15 nm are coated on Bk7 glasses through thermal evaporation. After doping gold of 5.2%, the grain size of the Ag film reduces from 13.6 nm to 9.1 nm, also the surface roughness decreases from 1.45nm to 0.94nm. A UV lamp is used as the irradiation light source to accelerate the corrosion process in the atmosphere. After 17h irradiation, the pure silver film surface turns dark, and the transmittances reduce from 350 nm to 500 nm, while the Ag—Au film degrades much less, almost negligibly after UV radiation. Additional x-ray photoelectron spectroscopy and atomic force micrographs data are provided to show atomic content of films and their surface morphologies. It is suggested that small grain size and high packing density of alloy film prevent reaction of silver with oxygen in the atmosphere, which leads to high stability of the Ag—Au film.

Agglomeration behavior of Ag films suppressed by alloying with some elements

Agglomeration behavior of co-sputtered Ag–Au, Ag–Cu and Ag–Al thin films was investigated. The results showed that Ag–Au films agglomerated during annealing in a similar way to pure Ag films, but a degree of suppression of this effect was observed in Ag–Cu and Ag–Al films. In particular, no void formation was observed in Ag–Al films for annealing temperatures up to 600 °C. Different mechanisms are proposed to explain agglomeration suppression and the prevention of Ag atom migration, including the precipitation Cu atoms in Ag–Cu films, and the formation of very thin Al-oxide layers at the film surface and at the interface with the substrate. The resistivity of Ag–Au film increased by annealing due to the agglomeration, but that of Ag–Cu and Ag–Al films did not. However, the resistivity of as-deposited Ag–Al film was too high to be reduced enough by annealing.

Surface plasmon resonance biosensor based on Hg/Ag–Au film

Mercury or silver was electrodeposited on an Au surface to form an Hg-Au or Ag-Au film. Wavelength-modulation SPR biosensors based on this Hg/Ag-Au film were then used to determine human IgG and rabbit IgG. When direct immunoreactions were performed on the Au sensing surface, the range of concentrations of human IgG and rabbit IgG that could be determined were 2.00-40.00 microg/ml and 2.50-40.00 microg/ml, respectively. When Hg was electrodeposited onto the Au film for 1200 s, the range of concentrations of human IgG and rabbit IgG that could be determined were 0.50-40.00 microg/ml and 0.63-40.00 microg/ml, respectively. When Ag was electrodeposited onto the Au film for 1500 s, the range of concentrations of human IgG and rabbit IgG that could be determined were 0.25-20.00 and 0.42-20.00 microg/ml, respectively. The biosensor based on Ag-Au film was therefore found to be the most sensitive of the three types of biosensor tested, giving limits of determination that were up to eight times lower than those obtained with a biosensor based on Au film alone.

Determination of lateral interaction energies in AgAu alloy films on Ru(0001) by Monte Carlo simulations

A lattice gas model with nonadditive lateral interactions is used to describe Ag, Au and AgAu bilayer films on a Ru(0001) substrate. By Monte Carlo simulations of adsorbate configurations and thermal desorption spectra of the Ag, Au and AgAu films, the microscopic interaction parameters of the gold and silver adatoms in the alloy film on Ru(0001) are obtained. The model reproduces experimental thermal desorption spectra of Ag, Au and AgAu films on Ru(0001) and also shows segregation of silver in the second monolayer of the alloy in agreement with experimental results. Based on perturbation theory, the configurational Gibbs free energy G of the AgAu monolayer alloy is calculated as a function of temperature and composition.

Morphological stability of AgAu multilayer on Si

The morphological stability of AgAu multilayers on Si has been studied by conventional and high-resolution transmission electron microscopy, X-ray diffraction and Auger electron spectroscopy. In samples annealed at 300 and 400°C, multilayered AgAu films form a continuous textured layer on Si. In sampled at 500°C, pinholes were found to develop in the AgAu films. Island structures were formed in samples annealed at 600°C. The improved stability is attributed to the intermixing of Au and Ag so that the (AuAg) Si interface is more stable than that of either the Au Si or Ag Si interface.