Molecular Layer Deposition Using Ring-Opening Reactions : Molecular Modeling of the Film Growth and the Effects of Hydrogen Peroxide

Published under an ACS AuthorChoice licenseNovel coating materials are constantly needed for current and future applications in the area of microelectronics, biocompatible materials, and energy-related devices. Molecular layer deposition (MLD) is answering this cry and is an increasingly important coating method for organic and hybrid organic-inorganic thin films. In this study, we have focused on hybrid inorganic-organic coatings, based on trimethylaluminum, monofunctional aromatic precursors, and ring-opening reactions with ozone. We present the MLD processes, where the films are produced with trimethylaluminum, one of the three aromatic precursors (phenol, 3-(trifluoromethyl) phenol, and 2-fluoro-4-(trifluoromethyl)benzaldehyde), ozone, and the fourth precursor, hydrogen peroxide. According to the in situ Fourier-transform infrared spectroscopy measurements, the hydrogen peroxide reacts with the surface carboxylic acid group, forming a peroxyacid structure (C(O)-O-OH), in the case of all three processes. In addition, molecular modeling for the processes with three different aromatic precursors was carried out. When combining these modeling results with the experimental research data, new interesting aspects of the film growth, reactions, and properties are exploited.Peer reviewe

Molecular layer deposition of "magnesicone", a magnesium-based hybrid material

Molecular layer deposition (MLD) offers the deposition of ultrathin and conformal organic or hybrid films which have a wide range of applications. However, some critical potential applications require a very specific set of properties. For application as desiccant layers in water barrier films, for example, the films need to exhibit water uptake and swelling and be overcoatable. For application as a backbone for a solid composite electrolyte for lithium ions on the other hand, the films need to be stable against lithium and need to be transformable from a hybrid MLD film to a porous metal oxide film. Magnesium-based MLD films, called "magnesicone", are promising on both these aspects, and thus, an MLD process is developed using Mg(MeCp)(2) as a metal source and ethylene glycol (EG) or glycerol (GL) as organic reactants. Saturated growth could be achieved at 2 to 3 angstrom/cycle in a wide temperature window from 100 to 250 degrees C. The resulting magnesicone films react with ambient air and exhibit water uptake, which is in the case of the GL-based films associated with swelling (up to 10%) and in the case of EG-based magnesicone with Mg(CO)(3) formation, and are overcoatable with an ALD of Al2O3. Furthermore, by carefully tuning the annealing rate, the EG-grown films can be made porous at 350 degrees C. Hence, these functional tests demonstrate the potential of magnesicone films as reactive barrier layers and as the porous backbone of lithium ion composite solid electrolytes, making it a promising material for future applications

Atomic layer deposition of thin films as model electrodes : a case study of the synergistic effect in Fe2O3-SnO2

Developing higher capacity electrode materials is a key challenge in battery advancement. Metal oxides undergoing conversion and/or alloying reactions offer high capacities, but suffer from volumetric changes and poor conductivities. However, combining several of these oxides can induce a synergistic effect, enhancing electrode characteristics. Using atomic layer deposition (ALD), carefully controlled model thin-film electrodes comprised of SnO2 and Fe2O3, and mixtures thereof are deposited to investigate length scales at which intermixing of the oxides is required to maximize this effect. ALD enables the synthesis of both intermixed structures and oxides where Fe, Sn, and O are mixed at the atomic scale and nanolaminated structures where Fe2O3 layer and SnO2 layers form a structure with well-defined interfaces. These model systems reduce the complexity of electrodes by eliminating the need for binders and additives and ensuring one-dimensional charge carrier diffusion. Using ALD enables us to study the influence of interfaces on electrode characteristics. It was found that intermixing of Fe2O3 and SnO2 at the atomic scale kinetically suppresses the alloying of Sn. In the nanolaminated superstructure, however, Sn alloying does take place, causing the well-defined interfaces to break down due to the volume changes brought about by alloying. As a consequence, the electrode capacity is rapidly fades, and thus, this structure type should be avoided. Here, the authors demonstrate that ALD is a unique tool with great potential for unraveling complex mechanisms in battery materials

Allometric biomass equations for Scots pine (Pinus sylvestris L.) seedlings during the first years of establishment in dense natural regeneration

International audienceA dense natural regeneration of Scots pine (Pinus sylvestris L.) exhibits a considerable biomass build-up in the first four years, with amounts of 7.03 Mg ha-1 for aboveground biomass, and 0.88 Mg ha-1 for coarse root biomass (> 1 mm). Power equations were developed, which relate collar diameter (ranging from 0.3 to 2.7 cm) and height to total aboveground and coarse root biomass of two, three and four-year-old seedlings in a regeneration of 16 seedlings m-2 at one site in Belgium. During the first years of establishment, seedling allometry changes with age, whilst the density remains constant. Biomass equations developed for one of the three ages can produce biased predictions for the other ages. Even when an equation is based on data for all ages and information on height is included, age still has to be considered as a potential predictor variable. For pooled ages, linear regression after logarithmic transformation of the power equation, selected other predictors than weighted non-linear regression. The former approach indicated significant interactions between predictors, while the latter does not reveal interactions.Équations d'allométrie de biomasse pour semis de pin sylvestre (Pinus sylvestris L.) dans les premières années d'établissement d'une régénération naturelle dense. Une régénération naturelle dense de pin sylvestre (Pinus sylvestris L.) montre une accroissement considérable de biomasse dans les quatre premières années, avec des quantités de 7,03 Mg ha-1 pour la biomasse aérienne et 0,88 Mg ha-1 pour la biomasse des grosses racines (> 1 mm). Des équations de type puissance mettant en relation le diamètre au niveau du collet racinaire (intervalle de 0,3 à 2,7 cm) et la hauteur avec la biomasse aérienne et la biomasse des grosses racines de semis de pin sylvestre âgés de deux, trois et quatre ans ont été développées dans une régénération d'une densité de 16 semis m-2 sur un site en Belgique. Entre la deuxième et la quatrième année, à densité stationnaire, la relation d'allométrie des semis change avec l'âge. Les équations de biomasse développées pour les semis d'un même âge, peuvent produire des prédictions erronées pour les autres âges. Même en utilisant des donnés de tous les âges et la variable hauteur, l'âge doit être considéré comme une variable potentielle dans l'analyse de régression. En utilisant des donnés de tous les âges, l'analyse de régression linéaire a retenu différentes variables que l'analyse de régression non-linéaire pondérée. La première désignait des interactions significatives, tandis que la dernière ne considère pas les interactions

Fuel for debating ancient economies. Calculating wood consumption at urban scale in Roman Imperial times

Estimating wood extraction rates from forests based on archaeological and historical evidence is an important step in evaluating the sustainability of past social-ecological systems. In this paper, we present a calculation tool to estimate human wood resource use for a selected location during a defined period in the past. We illustrate the method by its application to the ancient town of Sagalassos (South-west Anatolia, Turkey) during the Roman Imperial period, with a focus on pottery production and the Roman Baths. Based on archaeological data, thermodynamic formulas and calorific values, an estimation is provided of the amount of wood used within a time step of one year. Because quantitative information on ancient technology and lifestyle is rather scarce and uncertain, input values consist of ranges. In order to take this uncertainty into account, a Monte Carlo procedure is included, offering a probability distribution of possible outcomes. Our results indicate that wood consumption in 2nd century Sagalassos was quite high, with a lifestyle including frequent hot bathing, export driven pottery production and a climate that required heating during winter months. Based on the available woodland area, we conclude that the community of Sagalassos was intensively using the surrounding forests.status: publishe