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Cu nanoparticles were produced by using solid-state dewetting (dry) of a 1.3 nm Cu layer or laser ablation of a Cu solid target (wet) in acetone and methanol. The morphology and chemical composition of the nanoparticles were investigated as a function of the synthesis methods and their key parameters of the annealing temperature (200–500 °C) and the liquid environment during the ablation. Cu nanoparticles were then embedded in transparent conductive oxide (TCO) films as aluminum-doped zinc oxide (AZO) or zirconium-doped indium oxide (IZrO); the TCObott/Cu nanoparticle/TCOtop structures were synthesized with all combinations of AZO and IZrO as the top and bottom layers. The goal was to achieve a plasmonic and conductive structure for photovoltaic applications via a comparison of the involved methods and all fabricated structures. In particular, solid-state dewetting produced faceted or spherical (depending on the annealing temperature) nanoparticles with an average size below 150 nm while laser ablation produced spherical nanoparticles below 250 nm. Dry and wet plasmonic conductive structures as a function of the TCOs employed and the temperature of annealing could reach a sheet resistance of 86 Ω/sq. The energy band-gap Egap, absorbance, transmittance, and reflectance of the plasmonic conductive structures were investigated in the UV–vis–NIR range. They showed a dependence on the sequence of the top and bottom TCO, with best transmittances of 89.4% for the dry plasmonic conductive structure and 84.7% for the wet plasmonic conductive structure. The latter showed a higher diffused transmittance of between 10–20% in the visible range.

Glucose electrochemical sensors based on nanostructures of CuO/Cu(OH)2 onto graphene paper were prepared by thermal (solid) and nanosecond pulsed laser (molten phase) dewetting of a CuO layer 6 nm thin deposited by sputtering. Dewetted systems, obtained without the use of any binder, act as array of nanoelectrodes. Solid state and molten phase dewetting produce nanostructures of copper oxide-hydroxide with different average size, shape and surface composition. Molten phase dewetting originates particles with size below 100 nm, while solid state dewetting produces particles with average size of about 200 nm. Moreover, molten phase dewetting produce drop-shaped nanostructures, conversely nanostructures derived from solid state dewetting are multifaceted. X-ray photoelectron spectroscopy (XPS) characterization revealed that the surface of nanostructures is formed by a copper(II) species CuO and Cu(OH)2. Shape of anodic branch of the cyclic voltammograms of glucose in alkali solution evidenced a convergent diffusion mechanism. Analytical performances in amperometric mode are as good as or better than other sensors based on copper oxide. Amperometric detection of glucose was done at potential as low as 0.4 V versus saturated calomel electrode by both types of electrodes. Linear range from 50 μM to 10 mM, sensitivity ranging from 7 to 43 μA cm−2 mM−1 and detection limit of 7 μM was obtained. Good analytical performances were obtained by laser dewetted electrodes with a low copper content up to 1.2 by atoms percentage of the surface. Analytical performance of the proposed electrodes is compliant for the determination of glucose both in blood serum, saliva or tear.

This work presents an experimental study on the kinetic roughening for nanoscale-thick sputter-deposited Cu films on Si surface. In particular, the Cu films were deposited by using two different deposition rates and their Root-Mean-Square surface roughness was quantified by means of atomic force microscopy measurements. The results of these analyses are discussed on the basis of the dynamic scaling theory and, hence, evaluating the steady growth roughness exponent α and the dynamic growth roughness exponent β. We find a value for α = 0.89 ± 0.07 independent on the Cu deposition rate, while a value of β = 0.23 ± 0.03 at the lower Cu deposition rate (1.7 nm/min) and a value of β = 0.64 ± 0.05 at the higher Cu deposition rate (7.0 nm/min). At the lower deposition rate, the combined values of α = 0.89 ± 0.07 and β = 0.23 ± 0.03 suggest a growth process for the Cu film in thermodynamic equilibrium and dominated by surface diffusion. On the other hand, the combined values of α = 0.89 ± 0.07 and β = 0.64 ± 0.05 suggest a growth process again dominated by surface diffusion however with the occurrence of growing instabilities.

This work describes the effect of the annealing temperature on the size and wetting of nanostructures obtained on 4H–SiC substrate by the dewetting process of a deposited nanoscale-thick Ag film. The work focuses, in particular, on the difference between solid-state dewetting (below Ag melting temperature) and liquid-state dewetting (above Ag melting temperature). Following the deposition of a 58 nm-thick Ag film on the SiC substrate, annealings were perfomed at 800 °C, 850 °C and 885 °C so to induce the Ag film solid-state dewetting. In addition, annealing at 1040 °C was performed so to induce the Ag film liquid-state dewetting. The dewetting processes led to the formation of nanostructures on the SiC surface. Plan-view and cross-view scanning electron microscopy analyses were carried out to quantify the evolution of the average planar size and of the average contact angle (to the SiC surface) of the Ag nanostructures versus the annealing temperature. These analyses allowed us to extract information on the wetting behavior of the nanostructures on the SiC surface by calculating the temperature-dependent adhesion work. In fact, the nanostructures obtained by the 800 °C and 850 °C processes show mean contact angle of 118,9° and 117,4°, respectively, and mean work of adhesion of 0,45 and 0,48 J/m2, respectively. On the other hand, the nanostructures obtained by the 885 °C and 1040 °C show mean contact angle of 48,3° and 52,2° respectively, and work of adhesion of 1,45 and 1,40 J/m2, respectively. The variation of the wetting properties is identified in Si diffusion from the SiC substrate to the Ag nanostructures at the higher temperatures, as confirmed by energy dispersive x-ray analyses. Finally, the optical properties of the Ag nanostructures/SiC systems were probed by absorbance and transmittance measurements allowing to recognize the occurrence of a peak around 460 nm which is attributed to localized surface plasmon resonances due to the Ag nanostructures.

Aluminum doped Zinc oxide (AZO) is a promising transparent conductor for solar cells, displays and touch-screen technologies. The resistivity of AZO is typically improved by thermal annealing at temperatures not suitable for plastic substrates. Here we present a non-thermal route to improve the electrical and structural properties of AZO by irradiating the TCO films with O+ or Ar+ ion beams (30–350keV, 3×1015–3×1016ions/cm2) after the deposition on glass and flexible polyethylene naphthalate (PEN). X-ray diffraction, optical absorption, electrical measurements, Rutherford Backscattering Spectrometry and Atomic Force Microscopy evidenced an increase of the crystalline grain size and a complete relief of the lattice strain upon ion beam irradiation. Indeed, the resistivity of thin AZO films irradiated at room temperature decreased of two orders of magnitude, similarly to a thermal annealing at 400°C. We also show that the improvement of the electrical properties does not simply depend on the strain or polycrystalline domain size, as often stated in the literature.

Among transparent electrodes, transparent conductive oxides (TCO)/metal/TCO structures can achieve optical and electrical performances comparable to, or better than, single TCO layers and very thin metallic films. In this work, we report on thin multilayers based on aluminum zinc oxide (AZO), indium tin oxide (ITO) and Ag deposited by RF magnetron sputtering on soda lime glass at room temperature. The TCO/Ag/TCO structures with thicknesses of about 50/10/50 nm were deposited with all combinations of AZO and ITO as top and bottom layers. While the electrical conductivity is dominated by the Ag intralayer irrespective of the TCO nature, the optical transmissions show a dependence on the nature of the top and bottom TCOs, mainly due to the change in the reflectivity of the multilayers. Structural, electrical and optical properties are studied to optimize the structure for very thin transparent electrodes suitable for photovoltaic applications. © 2014 Springer-Verlag Berlin Heidelberg.

Laser irradiation of ZnO:Al/Ag/ZnO:Al transparent contacts is investigated for segmentation purposes. The quality of the irradiated areas has been experimentally evaluated by separation resistance measurements, and the results are complemented with a thermal model used for numerical simulations of the laser process. The presence of the Ag interlayer plays two key effects on the laser scribing process by increasing the maximum temperature reached in the structure and accelerating the cool down process. These evidences can promote the use of ultra-thin ZnO:Al/ Ag/ZnO:Al electrode in large-area products, such as for solar modules. © 2013 Crupi et al.; licensee Springer.

Al-doped ZnO (AZO)/Ag/AZO multilayer coatings (50-70 nm thick) were grown at room temperature on glass substrates with different silver layer thickness, from 3 to 19 nm, by using radio frequency magnetron sputtering. Thermal stability of the compositional, optical and electrical properties of the AZO/Ag/AZO structures were investigated up to 400 °C and as a function of Ag film thickness. An AZO film as thin as 20 nm is an excellent barrier to Ag diffusion. The inclusion of 9.5 nm thin silver layer within the transparent conductive oxide (TCO) material leads to a maximum enhancement of the electro-optical characteristics. The excellent measured properties of low resistance, high transmittance in the visible spectral range and thermal stability allow these ultra-thin AZO/Ag/AZO structures to compete with the 1 μm thick TCO layer currently used in thin film solar cells. © 2012 Elsevier B.V. All rights reserved.