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The morphology of numerous nanocolumnar thin films deposited by the magnetron sputtering technique at oblique geometries and at relatively low temperatures has been analyzed for materials as different as Au, Pt, Ti, Cr, TiO, Al, HfN, Mo, V, WO and W. Despite similar deposition conditions, two characteristic nanostructures have been identified depending on the material: a first one defined by highly tilted and symmetric nanocolumnar structures with a relatively high film density, and a second one characterized by rather vertical and asymmetric nanocolumns, with a much lower film density. With the help of a model, the two characteristic nanostructures have been linked to different growth dynamics and, specifically, to different surface relaxation mechanisms upon the incorporation of gaseous species with kinetic energies above the surface binding energy. Moreover, in the case of Ti, a smooth structural transition between the two types of growths has been found when varying the value of the power used to maintain the plasma discharge. Based on these results, the existence of different surface relaxation mechanisms is proposed, which quantitatively explains numerous experimental results under the same conceptual framework.

Near infrared laser ablation of metals, specifically aluminum, has been systematically applied to generate surface roughness. Very high laser fluences may even lead to a so called “explosive” ablation regime where roughness becomes dramatically enhanced. In the present work we have developed an alternative methodology that, utilizing milder laser irradiation conditions (i.e. laser fluences from 0.37 to 0.72 J/cm2), renders aluminum surfaces with a dual-scale roughness character and Sp parameter values twice or even trice the value found in reference samples. This has been possible for aluminum substrates coated with a highly transparent aluminum oxynitride capping layer. The resulting surfaces, consisting of very rough partially oxidized aluminum with negligible amounts of nitrogen species, resulted highly hydrophobic and depicted long icing delay times as required for anti-icing applications. A correlation has been found between the wetting and anti-icing behaviors, the use of a capping layer and the laser irradiation conditions. To account for this exalted roughening phenomenon, we propose that the transparent capping layer confines the laser energy within the aluminum shallow zones, delays the formation of the plasma plume and produces an enhancement in the aluminum ablation, even at relatively low laser fluences.

Icing has become a hot topic both in academia and in the industry given its implications in transport, wind turbines, photovoltaics, and telecommunications. Recently proposed de-icing solutions involving the propagation of acoustic waves (AWs) at suitable substrates may open the path for a sustainable alternative to standard de-icing or anti-icing procedures. Herein, the fundamental interactions are unraveled that contribute to the de-icing and/or hinder the icing on AW-activated substrates. The response toward icing of a reliable model system consisting of a piezoelectric plate activated by extended electrodes is characterized at a laboratory scale and in an icing wind tunnel under realistic conditions. Experiments show that surface modification with anti-icing functionalities provides a synergistic response when activated with AWs. A thoughtful analysis of the resonance frequency dependence on experimental variables such as temperature, ice formation, or wind velocity demonstrates the application of AW devices for real-time monitoring of icing processes.

The low temperature formation of monoclinic VO2crystal domains in nanocolumnar vanadium/oxygen thin films prepared by magnetron sputtering at oblique angles is analyzed. The synthesis procedure involved the deposition of amorphous nanocolumnar VO1.9thin films at room temperature and its subsequent annealing at temperatures between 250 °C and 330 °C in an oxygen atmosphere. The thermochromic transition of these films was found at a temperature of 47 °C when the annealing temperature was 270 °C and 58 °C when the annealing temperature was 280 °C and 290 °C, presenting a clear drop of the optical transmittance in the infrared region of the spectrum. The significant downshift in the temperature window to obtain VO2in comparison with compact films and other strategies in literature is explained by the particular morphology of the nanocolumnar structures, which contains numerous defects along with open and embedded porosity.

The morphology and void connectivity of thin films grown by a magnetron sputtering deposition technique at oblique geometries were studied in this paper. A well-tested thin film growth model was employed to assess the features of these layers along with experimental data taken from the literature. A strong variation in the film morphology and pore topology was found as a function of the growth conditions, which have been linked to the different collisional transport of sputtered species in the plasma gas. Four different characteristic film morphologies were identified, such as (i) highly dense and compact, (ii) compact with large, tilted mesopores, (iii) nanocolumns separated by large mesopores, and (iv) vertically aligned sponge-like coalescent nanostructures. Attending to the topology and connectivity of the voids in the film, the nanocolumnar morphology was shown to present a high pore volume and area connected with the outside by means of mesopores, with a diameter above 2 nm, while the sponge-like nanostructure presented a high pore volume and area, as well as a dense network connectivity by means of micropores, with a diameter below 2 nm. The obtained results describe the different features of the porous network in these films and explain the different performances as gas or liquid sensors in electrochromic applications or for infiltration with nanoparticles or large molecules.

[ES] El dispositivo comprende un sustrato (2) piezoelécírico o ferroeiéctrico sobre el que se deposita hielo; unos electrodos (3), conectados al sustrato (2); un analizador de red vectorial (7), conectado a ios electrodos (3), y configurado para determinar la frecuencia de resonancia del sustrato (2); y un módulo de excitación que integra un generador de funciones (6) que comunica con el analizador de red vectorial (7) y está conectado a un amplificador (4) y este a su vez a los electrodos (3), El módulo de excitación está configurado para, mediante un interruptor automático (8), aplicar sobre los electrodos (3) una señal eléctrica AC de frecuencia coincidente con la frecuencia de resonancia medida en el analizador de red vectorial (7) y que cambia progresivamente a medida que se produce el proceso de deshielo., [EN] Disclosed is a device comprising: a piezoelectric or ferroelectric substrate (2) on which ice is deposited; electrodes (3), connected to the substrate (2); a vector network analyser (7), connected to the electrodes (3) and configured to determine the resonant frequency of the substrate (2); and an excitation module including a function generator (6) that communicates with the vector network analyser (7) and is connected to an amplifier (4), the amplifier being connected to the electrodes (3). The excitation module is configured to apply to the electrodes (3), by means of an automatic switch (8), an AC electrical signal having a frequency coinciding with the resonant frequency measured in the vector network analyser (7) and which changes gradually as the ice melts., [FR] Le dispositif comprend un substrat (2) piézoélectrique ou ferroélectrique sur lequel est déposée la glace ; des électrodes (3), reliées au substrat (2) ; un analyseur de réseau vectoriel (7), relié aux électrodes (3), et conçu pour déterminer la fréquence de résonance du substrat (2) ; et un module d'excitation qui intègre un générateur de fonctions (6) qui communique avec l'analyseur de réseau vectoriel (7) et est relié à un amplificateur (4) et ce dernier est à son tour relié aux électrodes (3). Le module d'excitation est conçu, par l'intermédiaire d'un interrupteur automatique (8), pour appliquer sur les électrodes (3) un signal électrique c.a. de fréquence correspondant avec la fréquence de résonance mesurée dans l'analyseur de réseau vectoriel (7) et qui change progressivement à mesure que se produit le processus de dégel.

We demonstrate the existence of stoichiometric variations at the nanoscale when growing nanocolumnar SiO thin films by reactive magnetron sputtering deposition at oblique angles. Results show stoichiometric variations in the range 0.3 < x < 1.3 when growing a SiO thin film. This agrees with results from a numerical growth model that obtains a shift of the stoichiometry in all nanocolumns from lower values at the side facing the Si target to higher values at the opposite side. The different momentum distribution of the gaseous reactive and sputtered species results in preferential incorporation of the latter at a particular side of the nanocolumns. The general occurrence of this mechanism during the reactive magnetron sputtering deposition of substoichiometric thin films at oblique angles is discussed.

It is demonstrated that, besides classical nanocolumnar arrays, the oblique angle geometry induces the growth of singular structures in the nanoscale when using wisely designed patterned substrates. Well-ordered array of crosses, cylindrical nanorods or hole structures arranged in square or hexagonal regular geometries are reported as examples, among others. The fundamental framework connecting substrate topography and film growth at oblique angles is presented, allowing the use of substrate patterning as a feasible thin film nanostructuring technique. A systematic analysis of the growth of TiO2 thin films on 4 different lithographic patterned substrates in 4 different scale lengths is also presented. A first conclusion is the existence of a height-based selective growth in the initial stages of the deposition, by which the film preferentially develops on top of the tallest substrate features. This behavior is maintained until the film reaches a critical thickness, the so-called Oblivion Thickness, above which the film topography becomes gradually independent of the substrate features. A general formula relating the spatial features of the pattern, the coarsening exponent and the Oblivion Thickness has been deduced.

Stainless steel (SS), widely used because of its outstanding corrosion protection properties, does not possess any particular anti-stain or anti-bacterial activity as required for household and sanitary applications. This work reports the fabrication of SS thin films that, keeping a similar corrosion resistance than the bulk material, presents hydrophobicity and anti-bacterial activity. These thin films are prepared at ambient temperature by physical vapor deposition (PVD), either electron beam evaporation (EBE) or magnetron sputtering (MS), at oblique angles (OAD). According to their scanning electron microcopy and atomic force microscopy analysis, the microstructure of the OAD-SS thin films consisted of tilted and separated nanocolumns defining a surface topology that, characterized by a high percentage of void space, varied with the deposition conditions and procedure, either EBE or MS. It has been shown that particularly the nanocolumnar MS-OAD thin films preserved and even improved the high corrosion resistance of compact SS, as determined by electrochemical analysis. Besides, all OAD-SS thin films depict hydrophobicity and a high antibacterial activity. These features, particularly remarkable for the MS-OAD thin films, have been related with their tip-like termination at the surface and the existence of large void spaces separating the nanocolumns. This topology appears to affect negatively the bacteria’s deployment onto the surface and therefore the survival rate. Differences in the corrosion and antibacterial performance between EBE and MS-OAD thin films have been related with the specificities of these two PVD methods of thin film preparation. A relatively high abrasion resistance, as determined by abrasion tests, supports the use of MS-OAD thin films for the protection of commodity materials.

Until recently, superhydrophobicity was considered as a hint to predict surface icephobicity, an association of concepts that is by no means universal and that has been proven to depend on different experimental factors and material properties, including the actual morphology and chemical state of surfaces. This work presents a systematic study of the wetting and freezing properties of aluminum Al6061, a common material widely used in aviation, after being subjected to nanosecond pulsed IR laser treatments to modify its surface roughness and morphology. All treated samples, independent of their surface finishing state, presented initially an unstable hydrophilic wetting behavior that naturally evolved with time to reach hydrophobicity or even superhydrophobicity. To stabilize the surface state and to bestow the samples with a permanent and stable hydrophobic character, laser-treated surfaces were covered with a thin layer of CFx prepared by plasma-enhanced chemical vapor deposition. A systematic comparison between freezing delay (FD) and wetting properties of water droplets onto these plasma-/polymer-modified laser-treated surfaces that, under conditions where a heterogeneous nucleation mechanism prevails, surface morphology rather than the actual value of the surface roughness parameter the key feature for long FD times. In particular, it is found that surface morphologies rendering a Cassie–Baxter wetting regime longer FDs than those characterized by a Wenzel-like wetting state. It is that laser treatment, with or without additional coverage with thin CFx coatings, affects wetting and ice formation behaviors and might be an efficient procedure to mitigate icing problems on metal surfaces.

A checklist of lichens and lichenicolous fungi of Sierra Nevada (Granada, southeast Spain) is presented, fruit of the collecting field trip carried out by the Spanish Lichen Society (SEL), complemented with literature references. The authors identified 194 taxa (171 lichens and 23 lichenicolous fungi). As a result of these identifications, 46 lichens and nine lichenicolous fungi are reported for the first time in Sierra Nevada. To date, the catalogue includes 551 taxa (528 lichens and 23 lichenicolous fungi). We confirm both the scarce presence of terricolous lichens in the cryoromediterranean belt and the absence of alpine belt terricolous lichens., Se presenta el catalogo de líquenes y hongos liquenícolas de Sierra Nevada (Granada, Sureste de España), fruto la prospección llevada a cabo por la Sociedad Española de Liquenología (SEL), complementada por la recopilación bibliográfica. Los autores identificaron un total de 194 taxones (171 líquenes y 23 hongos liquenícolas). Como resultado de esas identificaciones, se han encontrado 46 líquenes y 9 hongos liquenícolas que son nuevas citas para Sierra Nevada. Hasta la fecha, el catálogo incluye 551 taxones (528 líquenes y 23 hongos liquenícolas). Se confirma tanto la escasa presencia de líquenes terrícolas en el piso crioromediterráneo como la ausencia de líquenes terrícolas del piso alpino.

A pulsed laser ablation backwriting technique with high repetitive rates is implemented for the fabrication of silver coatings on glass surfaces. This method enables geometrical constraint-free deposition of metallic coatings. These exhibit sufficiently low electrical resistance to be used as electrodes in dielectric barrier discharge (DBD) plasma elements. Ambient air deposition of metallic silver electrodes on standard glass slides is explored using a sub-ns UV laser source, combined with hybrid beam scanning methods. The green nature of the overall deposition process includes a preliminary irradiation scan to homogenise the target surface before the subsequent backwriting step. Metal transfer is achieved by combining two phenomena within a simple beam scanning process: LIRT (laserinduced reverse transfer) of silver from the target to the glass, with a partial and secondary LIFT (Laser-Induced Forward Transfer) of silver from the glass to the target. Appropriate selection of pulse energy and pulse repetition rates, beam scanning velocities and target motion enable the growth of sufficiently thick Ag deposits on glass with the required low electrical resistivity and nearly 2D constraint-free geometry. This method avoids the use of vacuum and liquids, resulting in a cheap, facile and green methodology for the deposition of silver electrodes onto transparent substrate surfaces.

Nanostructuration and 2D patterning of thin films are common strategies to fabricate biomimetic surfaces and components for microfluidic, microelectronic or photonic applications. This work presents the fundamentals of a surface nanotechnology procedure for laterally tailoring the nanostructure and crystalline structure of thin films that are plasma deposited onto acoustically excited piezoelectric substrates. Using magnetron sputtering as plasma technique and TiO2 as case example, it is demonstrated that the deposited films depict a sub-millimetre 2D pattern that, characterized by large lateral differences in nanostructure, density (up to 50%), thickness, and physical properties between porous and dense zones, reproduces the wave features distribution of the generated acoustic waves (AW). Simulation modelling of the AW propagation and deposition experiments carried out without plasma and under alternative experimental conditions reveal that patterning is not driven by the collision of ad-species with mechanically excited lattice atoms of the substrate, but emerges from their interaction with plasma sheath ions locally accelerated by the AW-induced electrical polarization field developed at the substrate surface and growing film. The possibilities of the AW activation as a general approach for the tailored control of nanostructure, pattern size, and properties of thin films are demonstrated through the systematic variation of deposition conditions and the adjustment of AW operating parameters.

Infusion of low surface tension liquids in nanostructured surfaces is currently used to promote an anti-icing response, although the long term stability of these systems is often jeopardized by losses of the infused liquid. In this work, we propose an alternative to the infusion procedure to induce a more effective and long lasting anti-icing capacity. The method consists of a combination of surface nanostructuration with the chemical grafting of fluorocarbon molecules. Al6061 substrates have been subjected to laser roughening and further modified with a nanostructured AlO thin film to achieve a dual roughness and porous surface state. These surfaces have been subjected to a grafting treatment with perfluorooctyltriethoxysilane (PFOTES) vapor or, for comparative purposes, infused with a low surface tension liquid. A comparative analysis of the wetting, water condensation and anti-icing properties of these two systems showed an outstandingly better performance for the grafted surfaces with respect to the infused ones. Grafted surfaces were markedly superhydrophobic and required higher water vapor pressures to induce condensation. When looking for their anti-icing capacity, they presented quite long freezing delay times for supercooled water droplets (i.e. almost four hours) and exhibited a notably low ice accretion in a wind tunnel test. The high aging resistance and durability of these grafted surfaces and the reproducibility of the results obtained when subjected to successive ice accretion cycles show that molecular grafting is an efficient anti-icing methodology that, in aggressive media, may outperform the classical infusion procedures. The role of the fluorocarbon chains anchored on the surface in inducing an anti-icing functionality is discussed.

Addressing the problem of infection from the very first stage, i.e. inhibiting the formation of the bacterial biofilm, is a crucial step to prevent implant rejection. Nanocolumnar coatings exhibiting antibacterial properties have been fabricated by oblique deposition with magnetron sputtering [1]. The formation of nanocolumns (Fig.1) is the result of the effects of atomic shadowing when the atoms reach the surface along an inclined direction [2]. This technique is environmentally friendly: it is carried out at RT and does not involve chemical products (no recycling problems). Such methodology have been tested in a semiindustrial scale reactor, successfully coating in a single step the two sides of fixation plates for bone fractures [3]. Several in vitro experiments have been performed: analysis of bacterial adhesion and biofilm formation, analysis of osteoblast proliferation and mitochondrial activity, and osteoblasts–bacteria competitive growth scenarios, the latter also named “Race for the Surface” competition. In all these cases, the coatings show an opposite behavior toward osteoblast and bacterial proliferation [1,3]. Moreover, they are effective against Gram positive (S. aureus) and Gram negative (E. coli) bacteria [4]. Finally, when a synergic route is followed and the coatings are functionalized with Te nanorods, the antibacterial properties are enhanced, since Te adds contact-killing (Fig. 2), i.e. bactericidal effect, whilst the biocompatibility is preserved [4].

The nano-porosity embedded into the tilted and separated nanocolumns characteristic of the microstructure of evaporated thin films at oblique angles has been critically assessed by various variants of the positron annihilation spectroscopy. This technique represents a powerful tool for the analysis of porosity, defects and internal interfaces of materials, and has been applied to different as-deposited SiO and TiO thin films as well as SiO/TiO multilayers prepared by electron beam evaporation at 70° and 85° zenithal angles. It is shown that, under same deposition conditions, the concentration of internal nano-pores in SiO is higher than in TiO nanocolumns, while the situation is closer to this latter in TiO/SiO multilayers. These features have been compared with the predictions of a Monte Carlo simulation of the film growth and explained by considering the influence of the chemical composition on the growth mechanism and, ultimately, on the structure of the films.

Ceramic tiles are widely used as construction materials because of their outstanding mechanical properties (high strength, hardness, toughness and abrasion resistance), chemical inertness and aesthetic appearance. Concomitantly, a variety of new functionalities have been demonstrated during recent years, by developing appropriate frit and glaze compositions. Laser processing has been intensively utilized to improve surface characteristics, either applying ablative laser regimes or intense mid-IR emission beams that enable high temperature surface melting. In this context, in addition to the numerous thermal annealing procedures reported in the literature and applied to industry to modify the surface properties of ceramics, a novel Laser Furnace (LF) method has been recently patented. It enables modifying the surface finish of solids by inducing high temperature (1500-3000 °C) reactions at surfaces and interfaces, while maintaining volume temperatures at relatively low values (i.e. below 1200 °C). This paper deals with the application of this laser technology to the coloring of ceramic tiles previously deposited with either metal and oxide precursor thin films, or, alternatively with noble metal-organic layers. These layer/tile systems have been treated both, with nIR ns pulsed lasers and by cw CO2 lasers with emission in the mid-IR. The latter were coupled into a roller furnace to induce chemical processes which result in a variety of coloring effects.

Herein, we present the development of supported organic nanofabrics formed by a conformal polymer-like interconnection of small-molecule organic nanowires and nanotrees. These organic nanostructures are fabricated by a combination of vacuum and plasma-assisted deposition techniques to generate step by step, single-crystalline organic nanowires forming one-dimensional building blocks, organic nanotrees applied as three-dimensional templates, and the polymer-like shell that produces the final fabric. The complete procedure is carried out at low temperatures and is compatible with an ample variety of substrates (polymers, metal, ceramics; either planar or in the form of meshes) yielding flexible and low solid-fraction three-dimensional nanostructures. The systematic investigation of this progressively complex organic nanomaterial delivers key clues relating their wetting, nonwetting, and anti-icing properties with their specific morphology and outer surface composition. Water contact angles higher than 150° are attainable as a function of the nanofabric shell thickness with outstanding freezing-delay times (FDT) longer than 2 h at −5 °C. The role of the extremely low roughness of the shell surface is settled as a critical feature for such an achievement. In addition, the characteristic interconnected microstructure of the nanofabrics is demonstrated as ideal for the fabrication of slippery liquid-infused porous surfaces (SLIPS). We present the straightforward deposition of the nanofabric on laser patterns and the knowledge of how this approach provides SLIPS with FDTs longer than 5 h at −5 °C and 1 h at −15 °C.