arXiv subjects

F. Lallet

Publications and source records attributed to F. Lallet.

5 recordsLinked to original sources

arXiv2009

Sol-gel obtained YSZ nanocrystals on a substrate: a Monte Carlo approach of the crystallographic orientation

Sol gel obtained YZS (Yttria Stabilized Zirconia) nanocrystals have different morphologies when they grow on an $α$-alumina substrate after thermal treatment. When the substrate has planar defects, the nanocrystals grow in height and are narrow with a crystallographic orientation [111] in the vertical direction, while when the substrate is a perfect plane at the nanometric scale, the nanocrystals are rather extended over the substrate and do not grow in height, with a crystallo- graphic orientation [100] in the vertical direction. We present here a Monte Carlo approach which computes the actions of the substrate on the nanocrystals during thermal treatment: one action is the change in crystallographic orientation depending on the presence of defects and the other is the action on the morphology of the nanocrystals. The equivalent of thermal treatment is obtained after applying the Metropolis algorithm with adequate expressions of the energy depending on the inter-plane spacings and surface diffusion. Our numerical approach is in good agreement with the experimental results on the orientations and morphologies of the YSZ nanocrystals growing on a $α$-alumina substrate with planar defects

cond-mat.mtrl-sci↗

arXiv2008

Comparison between models of insulator and semiconductor thin films islanding

The 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 PVD-CVD and sol-gel synthesis approaches. We propose two simple physical models which are relevant to explain the fundamental differences between those methods.

cond-mat.mtrl-sci↗

arXiv2008

Interface energies of (100)_{YSZ} and (111)_{YSZ} epitaxial islands on (0001)_{alpha-Al_2O_3} substrates from first principles

We present an ab initio study of the interface energies of cubic yttria-stabilized zirconia (YSZ) epitaxial layers on a (0001)_{alpha-Al_2O_3} substrate. The interfaces are modelled using a supercell geometry and the calculations are carried out in the framework of density-functional theory (DFT) and the local-density approximation (LDA) using the projector-augmented-wave (PAW) pseudopotential approach. Our calculations clearly demonstrate that the (111)_{YSZ} || (0001)_{alpha-Al_2O_3} interface energy is lower than that of (100)_{YSZ} || (0001)_{alpha-Al_2O_3}. This result is central to understanding the behaviour of YSZ thin solid film islanding on (0001)_{alpha-Al_2O_3} substrates, either flat or in presence of defects.

cond-mat.mtrl-sci↗

arXiv2006

Micrometric particles twodimensional self-assembly during drying of liquid film

We computed the self-organisation process of a monodisperse collection of spherical micrometric particles trapped in a two-dimensional (2D) 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 diamond particles water based suspension ($d_{50} = 10 μm$) on a glass substrate. The drying of the suspension on a flat substrate leads to the formation of linear patterns and small clusters of micrometric particles distributed over the whole surface of the substrate, whereas the drying of the suspension on a 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 selforganized patterns.

cond-mat.soft↗

arXiv2005

Monte Carlo approach of the islanding of polycrystalline thin films

We computed by a Monte Carlo method derived from the Solid on Solid model, the evolution of a polycrystalline thin film deposited on a substrate during thermal treatment. 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. A good agreement was found regarding the morphology of numerical nanoislands at equilibrium, deduced from our model, and experimental nanoislands resulting from the fragmentation of YSZ thin films after thermal treatment.

cond-mat.mtrl-sci↗