Albert Carrilero

Ultrastable and Atomically Smooth Ultrathin Silver Films Grown on a Copper Seed Layer

An effective method to deposit atomically smooth ultrathin silver (Ag) films by employing a 1 nm copper (Cu) seed layer is reported. The inclusion of the Cu seed layer leads to the deposition of films with extremely low surface roughness (<0.5 nm), while it also reduces the minimum thickness required to obtain a continuous Ag film (percolation thickness) to 3 nm compared to 6 nm without the seed layer. Moreover, the Cu seed layer alters the growth mechanism of the Ag film by providing energetically favorable nucleation sites for the incoming Ag atoms leading to an improved surface morphology and concomitant lower electrical sheet resistance. Optical measurements together with X-ray diffraction and electrical resistivity measurements confirmed that the Ag film undergoes a layer-by-layer growth mode resulting in a smaller grain size. The Cu seeded Ag growth method provides a feasible way to deposit ultrathin Ag films for nanoscale electronic, plasmonic and photonic applications. In addition, as a result of the improved uniformity, the oxidation of the Ag layer is strongly reduced to negligible values.

Durable, superhydrophobic, antireflection, and low haze glass surfaces using scalable metal dewetting nanostructuring

AbstractIn this paper we report a multifunctional nanostructured surface on glass that, for the first time, combines a wide range of optical, wetting and durability properties, including low omnidirectional reflectivity, low haze, high transmission, superhydrophobicity, oleophobicity, and high mechanical resistance. Nanostructures have been fabricated on a glass surface by reactive ion etching through a nanomask, which is formed by dewetting ultrathin metal films (< 10 nm thickness) subjected to rapid thermal annealing (RTA). The nanostructures strongly reduce the initial surface reflectivity (∼4%), to less than 0.4% in the 390–800 nm wavelength range while keeping the haze at low values (< 0.9%). The corresponding water contact angle (θc) is ∼24.5°, while that on a flat surface is ∼43.5°. The hydrophilic wetting nanostructure can be changed into a superhydrophobic and oleophobic surface by applying a fluorosilane coating, which achieves contact angles for water and oil of ∼156.3° and ∼116.2°, respectively. The multicomponent composition of the substrate (Corning® glass) enables ion exchange through the surface, so that the nanopillars’ mechanical robustness increases, as is demonstrated by the negligible changes in surface morphology and optical performance after 5,000-run wipe test. The geometry of the nanoparticles forming the nanomask depends on the metal material, initial metal thickness and RTA parameters. In particular we show that by simply changing the initial thickness of continuous Cu films we can tailor the metal nanoparticles’ surface density and size. The developed surface nanostructuring does not require expensive lithography, thus it can be controlled and implemented on an industrial scale, which is crucial for applications.

Ultrathin metals and nano-structuring for photonic applications

Ultrathin materials and nano-structuring are becoming essential for the functionalization of optical surfaces. In the talk we will show how ultrathin metals can be exploited to create competitive transparent electrodes. At the same time they can be used to create nanostructured surfaces through mass scalable dewetting and etching techniques. After presenting the techniques, we will focus on the applications made possible by these materials and technologies, including self-cleaning or easy-to-clean display screens, efficient indium-free light emitting diodes and solar cells, antireflective structures for the laser industry and super-wetting surfaces for biology.

Superhydrophobic sputtered Al 2 O 3 coating films with high transparency

Summary form only given. Antireflection, self-cleaning coatings are widely used in various applications such as display panels, solar cells and optical lenses [1]. Many surfaces in nature are highly hydrophobic, making the deposition of a water drop almost impossible. Examples include the wings of butterflies and the leaves of plants. The best known illustration of a self-cleaning surface is indubitably that of the leaves of the lotus plant (Nelumbo nucifera) [2]. The key feature of the lotus leaf is a microscopically rough surface consisting of randomly distributed arrays of micropapillae with length-scale ranging from 5 to 200 microns. In order to obtain this biomimetic surface, several approaches have been proposed mostly based on sol-gel method [3,4].We have prepared superhydrophobic and highly oleophobic Al2O3 coating on fused silica substrates by the sputtering method. Deposition conditions, thickness and density of the film play critical roles in establishing the omniphobic behaviour of the substrates. By choosing the right process parameters, it is possible to form a nanoflower like structure (Fig. 1 left) of 20nm to 50nm with enough porosity to affect the surface free energy. The size of the microstructure is too small to scatter visible light leaving the material to have high transparency, 96% (Fig. 1 right), while maintaining low haze <; 2%. With the addition of a fluoropolymer coating, the water repellency became superhydrophobic with a contact angle greater than 165°. The oleophobicity of the coatings was greater than typical fluoropolymer coatings on flat surface with a contact angle equal to 130°.The capability of having high transparency, low haze and a high degree of water and oil repellency creates a great potential for an anti-reflection coating on glass. More details about the preparation method, surface structure, optical transparency, mechanical tests and contact angle for water and hexadecane of superhydrophobic Al2O3 thin film microstructures on fused SiO2 substrates, will be presented at the Conference.

Oxidation-free and ultra-smooth thin silver films grown on a copper seed layer

Silver (Ag) films have been the noble-metal choice in nanophotonics for different innovative applications. This work shows a simple and effective way to achieve atomically smooth, continuous Ag films (<; 10 nm) with the use of Cu (1 nm) seed layer. Compared to previous reports on Ge/Ag films, the use of Cu as seed layer material improves the surface roughness of Ag films (with RMS roughness <; 5Å over 10 μm x 10 μm area) and reduces the electrical resistivity by more than a factor of 2. In addition, due to the lower percolation thickness, the minimum thickness required to obtain a continuous Ag film down to 3 nm, which is much lower than reported in literature for Ag films, is produced.

CLEO ® /Europe — IQEC 2013 durable, superhydrophobic, antireflection and low haze glass surfaces using scalable metal dewetting nanostructuring

Nanostructures have been fabricated on a glass surface by reactive ion etching through a metallic nano-mask, refer to Figure 1. The metallic nano-mask is formed by dewetting ultrathin metal films (<;10nm thickness) subjected to rapid thermal annealing (RTA) [1].