Optimized Electroless Silver Coating for Optical and Plasmonic Applications

Abstract

Electroless metal deposition is a simple and convenient technique to fabricate metallic films and to provide isotropic metal functionalization of 3D structures with complex geometries. In this work, we describe the synthesis of silver coatings by means of a modified Tollens reaction and their use as optical coating. The chemical composition of the metallization bath is here addressed to optimize the metal coating deposition. The synthesis parameters have been tailored in order to deposit very smooth films which were characterized by scanning electron microscopy, atomic force microscopy, and optical spectroscopy. 2D diffraction gratings and sinusoidal plasmonic gratings were produced with the proposed method. Optical characterization confirmed the plasmonic activities of the resultant structures, proving the efficiency of the described method for optical applications. Thermal annealing was found to improve the surface roughness of the coating and therefore the optical properties of the plasmonic gratings

Towardsin vivointradermal surface enhanced Raman scattering (SERS) measurements: silver coated microneedle based SERS probe

“…The second is that Ag on the microneedle, synthesized by Tollen's method, has a larger surface roughness, as shown by the Ag morphologies in the FESEM image [ Figure 4(a) and (b)] that could lead to higher Raman intensity variations as compared to Ag film fabricated by the vaporization method [23]. The Tollen's method is chosen in this study, since this technique is cost-effective [24] in scaling up for potential mass production in the future, and flexible in the coating of three-dimensional geometries [24] with film morphologies that adhere to the substrates even after insertion and withdrawal [ Figure 4(b)]. In addition, this Ag morphology provides a local peak at about 800 nm in the extinction efficiency spectrum [ Figure 4(c)], which contributes to the effective SERS enhancement as shown in our experimental results (Figures 2 and 3).…”

Ultra-thin films for plasmonics: a technology overview

“…But, due to its reactivity, thin silver layers can be obtained with the bigger nomenclature of methods including electroless techniques [22,23,62] and CVD methods [63]. Epitaxial growth of silver films is, to our knowledge, the most advanced method to obtain thin smooth layers [64].…”

“…Silver can also be deposited chemically [22,23,62,72]. In this case, a reducing reaction is used to obtain thin silver films, reaching down to 10 nm thickness.…”

Grating-coupled surface plasmon resonance gas sensing based on titania anatase nanoporous films

“…[19] A phenylbridged polysilsesquioxane (ph-PSQ) film is suitable to be used as a patternable layer for the sinusoidal nanostructure fabrication and can stand high temperature thermal treatments. [20], [21] Ph-PSQ is an organicinorganic hybrid material synthesized at room temperature via a sol-gel process, starting from the 1,4-bis(triethoxysilyl)benzene monomer (Sigma-Aldrich). A solution of 1,4-bis(triethoxysilyl)benzene, ethanol (EtOH) and bi-distilled water was mixed in a monomer/H 2 O=1/6 molar ratio, using HCl as catalyst.…”