Alexandre DANESCU                                Version française               

Maître de Conférences ECL

INL
Site Ecole Centrale de Lyon
Batiment F7
36, Avenue Guy de Collongue
69134 Ecully
France

Tel : (33).04 72 18 60 58

E-mail : alexandre.danescu@ec-lyon.fr

Localisation : 2ème étage F7


Research activities

HDR

Department : Matériaux

Group : Hétéroépitaxie et Nanostructures

Activities :


Publications (last 5 years)

Articles Conférences invitées Communications
 

Articles (6)

Multiphase mean curvature flows with high mobility contrasts: A phase-field approach, with applications to nanowires
E. Bretin, A. Danescu, J. Penuelas, S. Masnou, , , , , , , , , , , , , , , ,
Journal of Computational Physics 365 324 2018 AbstractThe structure of many multiphase systems is governed by an energy that penalizes the area of interfaces between phases weighted by surface tension coefficients. However, interface evolution laws depend also on interface mobility coefficients. Having in mind some applications where highly contrasted or even degenerate mobilities are involved, for which classical phase field models are inapplicable, we propose a new effective phase field approach to approximate multiphase mean curvature flows with mobilities. The key aspect of our model is to incorporate the mobilities not in the phase field energy (which is conventionally the case) but in the metric which determines the gradient flow. We show the consistency of such an approach by a formal analysis of the sharp interface limit. We also propose an efficient numerical scheme which allows us to illustrate the advantages of the model on various examples, as the wetting of droplets on solid surfaces or the simulation of nanowires growth generated by the so-called vapor–liquid–solid method.       
Texture of Ge on SrTiO3(001) substrates: Evidence for in-plane axiotaxy
A. Danescu, J. Penuelas, B. Gobaut, G. Saint-Girons
Surface Science 644 13 2016       
Exact continuum intepolation of the linear chain with hyper-pre-stress
A. Danescu
International Journal of Fracture 202 237-244 2016       
On the propagation waves in the theory of thermoelasticity with microtemperatures
A. Danescu, S. Chirita
Mechanics Research Communications 75 1 2016       
Surface waves problem in a thermoviscoelastic porous half-space
S. Chirita, A. Danescu
Wave Motion 54 100-114 2015 AbstractIn this paper we analyze the surface Rayleigh waves in a half space filled by a linear thermoviscoelastic material with voids. We take into account the effect of the thermal and viscous dissipation energies upon the corresponding waves and, consequently, we study the damped in time wave solutions. The associated characteristic equation (the propagation condition) is a ten degree equation with complex coefficients and, therefore, its solutions are complex numbers. Consequently, the secular equation results to be with complex coefficients, and therefore, the surface wave is damped in time and dispersed. We obtain the explicit form of the solution to the surface wave propagation problem and we write the dispersion equation in terms of the wave speed and the thermoviscoelastic homogeneous profile. The secular equation is established in an implicit form and afterwards an explicit form is written for an isotropic and homogeneous thermoviscoelastic porous half-space. Furthermore, we use numerical methods and computations to solve the secular equation for some special classes of thermoviscoelastic materials considered in the literature. (C) 2014 Elsevier B.V. All rights reserved.       
Surface waves problem in a thermoviscoelastic half-space
A. Danescu, S. Chirita
Wave motion 54 100 2015       

Conférences invitées (3)

Hétérostructures à base de nanofils III-V
J. Penuelas, X. Guan, J. Becdelievre, L. Fouquat, P. Regreny, M. Gendry, G. Saint-Girons, R. Bachelet, A. Danescu, C. Botella, G. Grenet
Journées Surfaces et Interfaces Strasbourg, France January 24-26, 2018 AbstractLes nanofils semiconducteurs ont été intensivement étudiés au cours de ces dernières années en raison de leurs propriétés physiques originales. Contrairement à d’autres systèmes, les nanofils offrent la possibilité de créer des structures hétéroépitaxiales suivant deux géométries: radiale [1] (combinant les matériaux autour de l'axe de croissance des nanofils) et axiale [2] (combinant les matériaux le long de l'axe de croissance des nanofils). Dans les deux cas, un contrôle précis de la qualité des interfaces est nécessaire. Dans cette présentation, ces deux types d'hétérostructures seront présentés, en partant de nanofils de GaAs fabriqués par épitaxie par jets moléculaires. La première hétérostructure est formée d'une insertion axiale d’un segment Wurtzite dans des nanofils Zinc Blende. Nous montrerons qu'il est possible de contrôler la formation de telles structures en accordant les flux d’As et de Ga pendant la croissance. Ces travaux ouvrent la voie vers une ingénierie de la structure cristalline pour modifier les propriétés optiques et de transports [3]. La seconde hétérostructure consiste en un système hautement hétérogène: nanofils cœur (GaAs) / coquille (oxyde fonctionnel) et nanofils cœur (GaAs) / coquille (métal). En raison de la grande hétérogénéité, la croissance est difficile à réaliser car il est nécessaire d'éviter une oxydation indésirable pendant le transfert de l'échantillon et car le désaccord de maille est élevé. Une technique de protection des nanofils permettant d’obtenir des facettes de GaAs exemptes de contamination avant la croissance de la coquille est proposée [4].        
Growth of hybrid GaAs core / shell nanowires
X. Guan, J. Becdelievre, G. Saint-Girons, R. Bachelet, P. Regreny, C. Botella, G. Grenet, A. Danescu, B. Vilquin, P. Rojo Romeo, N. Chauvin, N. Blanchard, M. Silly, F. Sirotti, M. Gendry, J. Penuelas
GDR PULSE Marseille, France July 2016       
Semiconducting core / piezoelectric shell nanowires
J. Penuelas, X. Guan, J. Becdelievre, G. Saint-Girons, R. Bachelet, P. Regreny, C. Botella, G. Grenet, A. Danescu, B. Vilquin, P. Rojo Romeo, N. Chauvin, N. Blanchard, M. Silly, F. Sirotti, M. Gendry
PiezoNEMS workshop Grenoble, France December 1st 2016       

Communications (1)


Self-assembly “micro-origami” photon cages as hollow micro-resonators
A. Danescu, C. Chevalier, R. Artinyan, P. Regreny, G. Grenet, S. Callard, P. Rojo Romeo, X. Letartre, J.L. Leclercq
SPIE Microtechnologies Barcelona, Spain 4-6 mai 2015 AbstractSelective etching of pre-stressed multi-layered structures releases intrinsic stresses creating flexible macroscopic shapes (rolls, spirals, tubes…). Combining mechanical and photonic concepts, we develop an experimental approach by controlling material composition, mask design and etching process in order to obtain prescribed macroscopic 3D hollow optical micro-cavities. New photonic microstructures are proposed for an efficient light trapping in low index media. Cylindrical hollow cavities formed by bending a photonic crystal membrane are designed. Using numerical simulations, strong confinement of photons is demonstrated for very open resonators. The resulting strong light matter interaction can be exploited in optical devices comprising an active material embedded in a low index matrix like polymer or even gaz.