Centre d’Élaboration de Matériaux et d’Etudes Structurales


Accueil > Recherche > SINanO : Surfaces, Interfaces et Nano-Objets > Thématiques de Recherche

Surfaces, interfaces and grain boundaries : formation and properties

Selection of our most recent publications on this topic (from 2018) - The names of the team members are in blue


Multiple coupling modes to relax shear strain during grain boundary migration

 

Combe, N. ; Mompiou, F. & Legros, M.

Acta Materialia, 2021, 218, 117222

 

 

Shear-coupled grain boundary (GB) migration is an effective plastic mechanism in absence of dislocation activity, ie. more favorably in nanocrystalline metals. For a given GB, several stress induced migration mechanisms, referred as coupling modes participate to the decrease of the elastic energy produced by the shear. They operate through the nucleation and motion of interfacial defects known as disconnections, carrying elementary shear strain characterized by their Burgers vector. However, so far, the coupling modes have been studied only under a simple shear, a situation much less complex than expected in a strained polycrystal, where multiple components of the stress tensor are present. Here we propose a more systematic investigation of the coupling modes when a composite shear is applied. This promotes the activation of new coupling modes. Using Molecular Dynamics simulations, we evidence these multiple coupling modes and the operation of their associate disconnections. Moreover, we also show that, even at low temperature, GB migration may occur by the successive occurrence of two modes : the relaxed shear appears then as an effective parameter, resulting from the combination of two operating elementary mechanisms.

 


Migration couplée au cisaillement des joints de grains : le chaînon manquant dans le comportement mécanique des métaux à petits grains ?

 

Gautier, R. ; Rajabzadeh, A. ; Larranaga, M. ; Combe, N. ; Mompiou, F. & Legros, M.

Comptes Rendus. Physique, Académie des sciences, Paris, 2021, 22, 19-34

 

 

La réduction de la taille des grains est un moyen très efficace de bloquer les mouvements de dislocations et donc d’augmenter la résistance mécanique des métaux et alliages. Non seulement les joints de grains sont des obstacles connus pour les dislocations, mais lorsqu’ils atteignent des dimensions nanométriques, les cristallites deviennent généralement vides de dislocations, ce qui impose une contrainte supplémentaire pour développer la plasticité. Comprendre les mécanismes de déformation basés sur les joints de grains est devenu un enjeu majeur de la métallurgie physique. Ces mécanismes peuvent être multiples, impliquant des processus conservatifs et diffusifs qui sont mal compris. Une première approche qui consiste à transposer aux petites dimensions des mécanismes documentés à grande échelle comme le fluage de Coble, s’est avérée très limitée. Au contraire, la croissance des grains assistée par la contrainte ou la migration des joints de grains couplée au cisaillement, récemment observées dans les matériaux à petits grains à température ambiante, peuvent fournir une clé pour comprendre pleinement la “plasticité sans dislocation” dans les nanocristaux. Comme il s’agit d’un domaine relativement nouveau avec beaucoup plus de degrés de liberté, un effort de recherche continu doit être mené pour relier les propriétés mécaniques des nanocristaux à ces processus de plasticité basés sur les joints de grains.

 


Zinc-blende group III-V/group IV epitaxy : Importance of the miscut

 

C. Cornet, S. Charbonnier, I. Lucci, L. Chen, A. Létoublon, A. Alvarez, K. Tavernier, T. Rohel, R. Bernard, J.-B. Rodriguez, L. Cerutti, E. Tournié, Y. Léger, M. Bahri, G. Patriarche, L. Largeau, A. Ponchet, P. Turban, and N. Bertru

Phys. Rev. Materials 2020, 4, 053401

 

We clarify the central role of the miscut during group III-V/group IV crystal growth. We show that the miscut impacts the initial antiphase domain distribution, with two distinct nucleation-driven (miscut typically >1°) and terraces-driven (miscut typically <0.1°) regimes. It is then inferred how the antiphase domain distribution mean phase and mean lateral length are affected by the miscut. An experimental confirmation is given through the comparison of antiphase domain distributions in GaP and GaSb/AlSb samples grown on nominal and vicinal Si substrates. The antiphase domain burying step of GaP/Si samples is then observed at the atomic scale by scanning tunneling microscopy. The steps arising from the miscut allow growth rate imbalance between the two phases of the crystal and the growth conditions can deeply modify the imbalance coefficient, as illustrated with GaAs/Si. We finally explain how a monodomain III-V semiconductor configuration can be achieved even on low miscut substrates. Phys. Rev. Materials 4, 053401 (2020).

 


Density Functional Theory Study of the Spontaneous Formation of Covalent Bonds at the Silver/Silica Interface in Silver Nanoparticles Embedded in SiO2 : Implications for Ag+ Release

 

Hilal Balout, Nathalie Tarrat, Joël Puibasset, Simona Ispas, Caroline Bonafos, Magali Benoit

ACS Appl. Nano Mater. 2019, 2, 8, 5179–5189

 

Silver nanoparticles (AgNPs) are widely used in the health-care sector and industrial applications because of their outstanding antibacterial activity. This bactericidal effect is mainly attributed to the release of Ag+ ions in an aqueous medium, the first step of which is the dissolution of the AgNP via the oxidation of its surface by O2. With the aim of designing more durable and less toxic antibacterial devices, it is desirable to fine-tune the rate of Ag+ release into the surrounding environment. This can be achieved by choosing an adequate coating of the AgNPs, e.g., by embedding the nanoparticles in a silica matrix. In a previous work (Pugliara, A. ; et al. Sci. Total Environ.2016, 565, 863), we have shown that the toxic effect on algae photosynthesis of small AgNPs (size <20 nm) embedded in silica layers is preserved, provided that the distance between the AgNPs and the silica free surface is below ≈6–7 nm. Better control of the Ag+ release rate in these systems requires a better understanding of the elementary mechanisms at play concerning both the detachment of the Ag ions from the AgNPs and their diffusion through SiO2. A first step in this direction consists in characterizing the interface between the AgNPs surface and the silica matrix. In this context, periodic density functional theory calculations have been performed on model systems representing the interfaces between amorphous silica and the three crystalline facets of AgNPs, i.e., Ag(111), Ag(110), and Ag(100). Spontaneous breaking of the Si–O bonds and the formation of two O–Ag and one Si–Ag bonds are observed in 50% of the investigated interfaces, corresponding to 1.8 bonds/nm2 on average. The covalent nature of the bonds between Ag and O and between Ag and Si is highlighted by analysis of the electronic structure of the interfaces.

 


Heterogeneous disconnection nucleation mechanisms during grain boundary migration

 

N. Combe, F. Mompiou, and M. Legros

Phys. Rev. Materials 2019 3, 060601(R)

 

Heterogeneous nucleation of a mobile μ⟨110⟩ disconnection from a sessile disconnection
Heterogeneous nucleation of a mobile μ⟨110⟩ disconnection from a sessile disconnection

Shear-coupled grain boundary (GB) migration has been evidenced as an efficient mechanism of plasticityin the absence of dislocation activity. The GB migration occurs through the nucleation and motion ofdisconnections. Using molecular simulations, we report a detailed study of the elementary mechanisms occurringduring heterogeneous disconnection nucleation. We study the effect of a preexisting sessile disconnection in asymmetric S17(410) [001] tilt GB on the GB migration mechanism. Shearing this imperfect GB induces itsmigration and reveals a new GB migration mechanism through the nucleation of a mobile disconnection from thesessile one. Energy barriers and yield stress for the GB migrations are evaluated and compared to the migrationof a perfect GB. We show that the migration of the imperfect GB is easier than the perfect one and that a sessiledisconnection can operate as a source of disconnection driving the GB migration. This GB migration mechanismhas been observed on two other high-angle GBs.

 


Shape transition in InAs nanostructures formed by Stranski-Krastanow growth mode on InP (001) substrate

 

A. Ponchet, L. Pedesseau, A. Le Corre, C. Cornet, and N. Bertru

Appl. Phys. Lett. 2019, 114, 173102

 

Equilibrium shape (length, width and height) as a function of the volume of InAs nanostructures grown on InP(001) substrates
Equilibrium shape (length, width and height) as a function of the volume of InAs nanostructures grown on InP(001) substrates

The shape of InAs nanostructures formed by molecular beam epitaxy on a (001) InP substrate in the Stranski-Krastanow growth mode is studied. A transition from wires to round-shaped islands is observed as a function of the amount of InAs deposited. It is attributed to the non-equivalent energies of the A and B facets existing in zinc blende materials (facets along [1-10] and [110], respectively). This surface energy anisotropy is considered to determine the nanostructure equilibrium shape from the balance between the elastic energy and the surface energy. At low volumes, the most energetically favorable shape is the wire-like shape, while at high volumes, the equilibrium shape is the island-like shape. The calculated sizes for which the shape changes are in good agreement with experimental sizes. The low lattice mismatch and the low surface energy of (114)A InAs facets around 41 meV/A2, as obtained from density functional theory calculations, enhance this effect in the InAs/InP system. Published in Appl. Phys. Lett. 114, 173102 (2019) .

 


Interface energy analysis of III–V islands on Si (001) in the Volmer-Weber growth mode

 

A. Ponchet, G. Patriarche, J. B. Rodriguez, L. Cerutti and E. Tournié

Appl. Phys. Lett. 2018, 113, 191601

 

The in-plane shape of III-V on Si islands varies from quasi rounded to elongate depending on whether the adhesion is low or high.
The in-plane shape of III-V on Si islands varies from quasi rounded to elongate depending on whether the adhesion is low or high.

The experimental island shapes of III–V islands grown on silicon (001) in the Volmer-Weber growth mode are analyzed in the frame of the theory of wetting in crystals. A reverse Wulff-Kaishew (or Winterbottom) construction is used in order to access interfacial energy. We apply this approach to AlSb and GaSb islands on (001) Si grown by molecular beam epitaxy and observed by scanning transmission electron microscopy. Experimental ratios between energies of (001), (110), (111)A, and (111)B surfaces are established. Interface energies are then quantitatively estimated for GaSb/Si and AlSb/Si interfaces. The differences in the shape of GaSb and AlSb islands, which are consistently reported in the literature, can be clearly attributed to a higher energy for the GaSb/Si interface compared to the ASb/Si one and not to different adatom diffusion lengths. The difference in interface energies is quantified, and its origin at the microscopic level is discussed. Published in Appl. Phys. Lett. 113, 191601 (2018).

 


A Stress-Free and Textured GaP Template on Silicon for Solar Water Splitting

 

Ida Lucci, Simon Charbonnier, Maxime Vallet, Pascal Turban, Yoan Léger, Tony Rohel, Nicolas Bertru, Antoine Létoublon, Jean-Baptiste Rodriguez, Laurent Cerutti, Eric Tournié, Anne Ponchet, Gilles Patriarche, Laurent Pedesseau and Charles Cornet

Adv. Funct. Mater. 2018, 28, 1801585

 

This work shows that a large-scale textured GaP template monolithically integrated on Si can be developed by using surface energy engineering, for watersplitting applications. The stability of (114)A facets is first shown, based on scanning tunneling microscopy images, transmission electron microscopy, and atomic force microscopy. These observations are then discussed in terms of thermodynamics through density functional theory calculations. A stress free nanopatterned surface is obtained by molecular beam epitaxy, composed of a regular array of GaP (114)A facets over a 2 in. vicinal Si substrate. The advantages of such textured (114)A GaP/Si template in terms of surface gain, band lineups, and ohmic contacts for water-splitting applications are finally discussed. Published in Adv. Funct. Mater. 2018, 1801585.

 


Universal description of III-V/Si epitaxial growth processes

 

I. Lucci, S. Charbonnier, L. Pedesseau, M. Vallet, L. Cerutti, J.-B. Rodriguez, E. Tournié, R. Bernard, A. Létoublon, N. Bertru, A. Le Corre, S. Rennesson, F. Semond, G. Patriarche, L. Largeau, P. Turban, A. Ponchet, and C. Cornet

Phys. Rev. Materials 2018, 2, 060401(R)

 

Prediction from surface and interface energies of the 3D growth mode of GaP on Si
Prediction from surface and interface energies of the 3D growth mode of GaP on Si

Here, we experimentally and theoretically clarify III-V/Si crystal growth processes. Atomically resolved microscopy shows that monodomain three-dimensional islands are observed at the early stages of AlSb, AlN, and GaP epitaxy on Si, independently of misfit. It is also shown that complete III-V/Si wetting cannot be achieved in most III-V/Si systems. Surface/interface contributions to the free-energy variations are found to be prominent over strain relief processes. We finally propose a general and unified description of III-V/Si growth processes, including a description of the formation of antiphase boundaries. Published in PHYSICAL REVIEW MATERIALS 2, 060401(R) (2018)

 


Noble Metal Nanocluster Formation in Epitaxial Perovskite Thin Films

 

M. Lee, R. Arras, R. Takahashi, B. Warot-Fonrose, H. Daimon, M.J. Casanove, M. Lippmaa

ACS Omega 2018, 3, 21692173

 

We studied the synthesis of nanocomposite materials consisting of noble metal clusters embedded in an oxide semiconductor matrix. The embedded nanostructures form in a simple self-organized single-step growth process. The primary interest is in developing materials for photo-electrochemical energy conversion where spatially inhomogeneous band structures can enhance photogenerated charge separation and carrier extraction from a semiconductor. We show that spontaneous segregation of metallic Ir occurs during the initial growth of an Ir:SrTiO3 thin film. Cross-sectional transmission electron microscopy suggests that the nanoscale Ir clusters are epitaxial with the host lattice, and their presence is not detectable by surface morphology measurements. Published in ACS Omega 3 ,2169-2173 (2018).