International audiencetreatment of a polycrystalline thin film deposited on a substrate with no further deposition. Two types of substrates have been studied: a single crystalline substrate with no defects and a single crystalline substrate with defects. We obtain islands which are either flat i.e., with a height which does not overcome a given value or grow in height like narrow towers. The numerical results have been qualitatively compared with experimental data: the fragmentation after thermal treatment of an yttria stabilized zirconia thin film deposited on an Al2O3 substrate. A good agreement was found regarding the morphology of simulated and experimental nanoisland
We computed the self-organization process of a monodisperse collection of spherical micrometer-sized particles trapped in a two-dimensional thin liquid film isothermally dried on a chemically inert substrate. The substrate is either flat or indented to create linear stripes on its surface. The numerical results are illustrated and discussed in the light of experimental ones obtained from the drying of a water-based suspension of diamond particles (d{50}=10 microm) on a glass substrate. The drying of the suspension on a flat substrate leads to the formation of linear patterns and small clusters of micrometer-sized particles distributed over the whole surface of the substrate, whereas the drying of the suspension on an indented substrate leads to the aggregation of the particles along one side of the stripe which has a higher roughness than the other side of the stripe. This is an easy experimental way to obtain colloidal self-organized patterns.
We present an ab initio study of the interface energies of cubic yttria-stabilized zirconia ͑YSZ͒ epitaxial layers on a ͑0001͒ ␣-Al 2 O 3 substrate. The interfaces are modeled using a supercell geometry and the calculations are carried out in the framework of density-functional theory ͑DFT͒ and the local-density approximation ͑LDA͒ using the projector augmented wave ͑PAW͒ pseudopotential approach. Our calculations clearly establish the existence of competing growth mechanisms between ͑111͒ YSZ ʈ ͑0001͒ ␣-Al 2 O 3 and ͑100͒ YSZ ʈ ͑0001͒ ␣-Al 2 O 3 interfaces. This result is central to understanding the behavior of YSZ thin solid film islanding on ͑0001͒ ␣-Al 2 O 3 substrates, either flat or in presence of defects.
International audienceThe synthesis of self-organized quantum dots (QD's) can be achieved through bottom up layer by layer deposition processes as chemical vapor deposition (CVD) or physical vapor deposition (PVD). However, QD's may also be synthesized via sol-gel route, which involves a spontaneous evolution from thin films to discrete QD's without further deposition. The aim of the paper is to discuss and compare the physical phenomena involved in QD's formation which initiate from thin film surface roughening between PVDCVD and sol-gel synthesis approaches. We propose two simple physical models which are relevant to explain the fundamental differences between those methods
We compared two models of aggregation which represent the sol gel transition of base-catalyzed colloidal gels. The two models are a Langevin dynamics approach of this transition and the DLCA model (diffusion limited cluster-cluster aggregation). For large numbers of particles, we compared the fractal dimension of the gelling network via the structure factor of the bulk. We observed that the Langevin dynamics approach did give more realistic fractal dimension than the DLCA model. This is due to the fact that Langevin dynamics evolves as a function of a physical time.
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