Long term directional wave recording in the Northern Adriatic Sea

We report on the instrumental system used on an oceanographic tower for the directional measurement of wind waves. The associated time series is one of the longest ones in the world. After a compact description of the instrumental part, we present some long term statistics of the wave conditions in the Northern Adriatic Sea. Then we discuss the applications of the results and the possible evolution of the system

Microplastic Contamination in Protected Areas of the Gulf of Venice

We investigated the concentration and composition of plastics in 7 Special Areas of Conservation (SACs) from the Gulf of Venice (northern Adriatic Sea). A total of 42 sediment samples were analyzed from 21 sites from 2017 to 2018. All sites except one were found to be polluted by plastics, with density ranging between 2250 and 28.4 items kg−1. Microplastics ranged from 100 to 61.6% of the collected plastics. Fragments were more represented than filaments. The greatest plastic concentrations were generally recorded in western SACs. Identification through FT-IR spectroscopy evidenced the presence of 8 polymer types: in western SACS, the majority were low-density polymers (PE, PP, PS, and TPU), while in eastern SACs they were high-density polymers (PET, nylon, and PVC). In addition to the role of large rivers (all on the western side of the Gulf) in conveying plastics into the sea, a possible role of the cyclonic water circulation of the northern Adriatic Sea on distribution and composition of plastics along the Gulf coasts is likely

Interplay between deoxidation and dewetting for ultrathin SOI films

International audienceSince a few years there have been many efforts for studying solid state dewetting that means the spontaneous agglomeration of a metastable film into an assembly of 3D crystallites [1–3]. Since the size of the so-formed 3D crystallites depends on the initial thickness of the film [3–6], solid state dewetting of ultra-thin films is a promising method for producing nanodots [7, 8]. Many studies thus focused on the effect of the film thickness on the dewetting morphologies. Generally thicker films dewet by void nucleation and opening process forming then well-organized 3D islands [1–3]. In contrast to this thinner films tend to form more complex structures [9–14]. For instance Kinetic Monte Carlo simulations have shown that a 3 ML-thick film dewets by void nucleation whereas a 1 ML-thick film dewets by forming a labyrinthine pattern of bilayer islands [10, 11]. In the literature the specific behavior of the thinner films has been attributed to barrierless void nucleation [15], spinodal dewetting (enhanced sensitivity to thickness or thermal fluctuations) [16], short range effect of the wetting potential [17, 18] or local stresses [14, 19]. Recently we investigated dewetting properties of Silicon-on-Insulator (SOI) samples capped by a chemically-prepared oxide layer. We thus reported that films thicker than 8 nm dewet in four steps and break down into self-organized 3D crystals whereas films thinner than 6 nm dewet by labyrinthine formation [9]. In this paper we show that this thin film effect is actually due to a subtle interplay between film deoxidation and film dewetting. Indeed the temperature at which a film dewets (T dew (h)) depends on its thickness h whereas the deoxidation temperature (T deox) is a constant. We thus show that if T dew (h) > T deox SOI dewetting occurs by void opening and leads to 3D crystals whereas if T dew (h) < T deox SOI dewetting leads to labyrinthine morphologies. In other words, the dewetting of the thicker films does not depend on the oxide cap (that decomposes before dewetting and thus only depends on the surface energy gain due to the disappearance of the Si surface with respect to the uncovered bare substrate) while the dewetting of the thinner films depends on the deoxidation (since only the clean deoxidized parts of the silicon film can dewet). We use LEEM to investigate in-situ and in real time the decomposition of the oxide as well as the dewetting of the SOI films. We define the deoxidation temperature T deox as the temperature at which LEEM enables to see void opening in the oxide cap layer with subsequent silicon film appearance. In a similar manner, the dewet-ting temperature T dew is defined as the temperature at which the amorphous SiO 2 substrate starts becoming visible by retraction of the silicon film. Obviously both temperatures T deox and T dew do not correspond to phase transitions and thus depend on the observation means. However since measured in the same experimental conditions they can be compared without any ambiguity. The SOI samples used in the experiments (12 nm Si on top of 25 nm SiO 2) were prepared as described elsewhere [20]. By means of repeated etching and oxidation cycles a stepwise thinning of the samples is possible to produce films of a certain thickness with a very high accuracy ending with a final oxidation step. Since this protective oxide layer is produced with the same wet chemical oxidation for each Si film thickness the thickness of the oxide is the same for all samples. Ellipsometry measurements have proven that the oxide thickness is constant with approximately 1 nm. FIG. 1. Temperature at which the initial deoxidation (black) and dewetting (red) was observed depending on the Si film thickness. Dewetting velocities are in the range of 1 to 8 nm s. The data point at 21.6 nm was obtained using a SOI sample of 22 nm Si on top of 150 nm SiO2. In Figure 1 are thus reported T deox and T dew as a function of the Silicon film thickness. As expected, the decomposition temperature of the capping oxide does not depend on the thickness of the silicon film and is rather constant at T deox =760 • C whereas T dew decreases as h n with n = 0.08 ± 0.01 comparable to [21, 22] where exponents n = 0.15 ± 0.01 have been reported. In the following we will report dewetting morphologie

Dewetting of patterned solid films: Towards a predictive modelling approach

International audienceOwing to its ability to produce an assembly of nanoislands with controllable size and locations, the solid state dewetting of patterned films has recently received great attention. A simple Kinetic Monte Carlo model based on two reduced energetic parameters allows one to reproduce experimental observations of the dewetting morphological evolution of patterned films of Si(001) on SiO2 (or SOI for Silicon-on-Insulator) with various pattern designs. Thus, it is now possible to use KMC to drive further experiments and to optimize the pattern shapes to reach a desired dewetted structure. Comparisons between KMC simulations and dewetting experiments, at least for wire-shaped patterns, show that the prevailing dewetting mechanism depends on the wire width

The liquid metastable miscibility gap in the Cu-Co-Fe system

Cu-Co-Fe alloys undercooled below a certain temperature display demixing of the liquid, followed by coagulation before dendritic solidification. In this article high temperature phase equilibria in Cu-Co-Fe samples have been precisely determined by DSC. Special attention has been paid to the liquid-liquid phase separation and on its effect on the formation of microstructures. The measured transformation temperatures have also been used to update the description of the ternary phase diagram