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Academic literature on the topic 'Contrainte épitaxiale'
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Journal articles on the topic "Contrainte épitaxiale"
Arenal de la Concha, R., I. Schuster, D. Halley, A. Marty, and P. Bayle-Guillemaud. "Alliages magnétiques FePd et FePt en couches minces sous contrainte épitaxiale : mise en ordre en température et propriétés magnétiques." Journal de Physique IV (Proceedings) 12, no. 6 (July 2002): 25–38. http://dx.doi.org/10.1051/jp4:20020209.
Full textDissertations / Theses on the topic "Contrainte épitaxiale"
Solere, Alexis. "Instabilité de croissance dans les couches épitaxiées contraintes." Ecully, Ecole centrale de Lyon, 1999. http://www.theses.fr/1999ECDL0053.
Full textUnstability in the growth of epitaxially strained layers. Study by scanning tunneling microscopy of the system In1-xGaxAs / InP (001). The heteroepitaxial growth of semiconducting strained films shows a morphological unstability: the growth evolves from a layer-by-layer growth mode towards a three-dimensional mode with islands. Understanding the physics of this phenomenon is of a great importance as for the realization of flat interfaces that is sough-after for microelectronic applications as for the elaboration of nanostructures whose quantum character could drive to novel applications. The scanning tunneling microscopy (STM) study developed in this work concerns the III-V system In1-xGaxAs strained on InP (001) which, according to the chosen composition x, allows to obtain a compressive (x<0,47;ε<0) or a tensile (x>0,47;ε>0) strain. The roles of the sign and of the intensity of the strain are thus studied by following the growth behavior of four strained systems: GaAs (ε=+3,8%), In0,25Ga0,75As (ε=-2%), In0,82Ga0,18As (ε=-2%) and As(ε=-3,1%). Moreover, the importance of the supersaturation conditions on the layers growth has been proved by using two different protocols: supersaturation of arsenic as a first and cationic supersaturation as the other. In standard growth conditions, with an excess of arsenic prssure, an abrupt 2D-3D transition in the growth mode is observed in the compression case; it leads to the formation of wire-shaped three-dimensional islands that are extended in the [1 1 0] direction and spread out the whole surface. The starting of the unstability is all the earlier and the anisotropic shape is all the more pronouced since the strain is strong. In the tension case, the unstability appears through a continuous roughening process which results, at the end, in a 3D anisotropic [11 ̅0]-oriented morphology. When the elements III are in majority (cation-rich stabilization), the layer-by-layer growth mode is preserved, and this until the first plastic defaults occur. Such 2D morphologies are stable against thermal annealing. The whole results can be described through a model, considering the competition between step energy-steps are necessary to create 3D structures- and relaxed strain energy-relaxation becomes possible through steps creation. The formation of wire-shaped structures can be explained by the large difference in the energy of A-steps ([11 ̅0]-oriented) and B-steps([11 ̅0]-oriented). The absence of 2D-3D transition can be sucessfully interpreted by a high step energy on cation-stabilized surfaces; the 2d-3D transition cannot then occur before the first plastic defaults appear. Also, the non-symmetrical behavior between compression and tension would indicate a weaker step energy in the tensile case than in compression; the steps creation in layers under tension would always be favored. Moreover, the model points out local overstrain effects, at the bottom of the steps, which must be considered to justify the formation of wire-shaped structures during the 2D-3D transition
Zahradník, Martin. "Dynamic control of magnetization for spintronic applications studied by magneto-optical methods." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS155/document.
Full textTwo important mechanisms in preparation of ultrathin films of magnetic oxides were systematically investigated in this work. First, influence of epitaxial strain on resulting magneto-optical properties of La₂/₃Sr₁/₃MnO₃ (LSMO) ultrathin films was studied. The investigated films were grown by pulsed laser deposition on four different substrates, providing a broad range of induced epitaxial strains. Magnetic properties were found to deteriorate with increasing value of the epitaxial strain, as expected due to the unit cell distortion increasingly deviating from the bulk and effect of the magnetically inert layer. A combination of spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy was used to determine spectra of the diagonal and off-diagonal elements of permittivity tensor. The off-diagonal elements confirmed presence of two previously reported electronic transitions in spectra of all films. Moreover, they revealed another electronic transition around 4.3 eV only in spectra of films grown under compressive strain. We proposed classification of this transition as crystal field paramagnetic Mn t2g → eg transition, which was further supported by ab initio calculations. A key role of strain in controlling electronic structure of ultrathin perovskite films was demonstrated. Dynamic application of strain via use of piezoelectric underlayer remained inconclusive, requiring further improvement of the strain transfer from the piezoelectric layer into the LSMO. Second, influence of substrate miscut on magnetization dynamics in SrRuO₃ (SRO) was studied. As expected we found that high miscut angle leads to suppression of multi-variant growth. By means of magnetic force microscopy we showed that presence of multiple SRO variants leads to higher density of defects acting as pinning or nucleation sites for the magnetic domains, which consequently results in deterioration of magnetic properties. We demonstrated that use of vicinal substrate with high miscut angle is important for fabrication of high quality SRO ultrathin films with low density of crystallographic defects and excellent magnetic properties
Halley, David. "Croissance, mise en ordre chimique et relaxation des contraintes épitaxiales dans des alliages FePd et FePt." Phd thesis, Université Joseph Fourier (Grenoble), 2001. http://tel.archives-ouvertes.fr/tel-00757727.
Full textFeltin, Eric. "Hétéro-épitaxie de Nitrure de Gallium sur substrat de silicium (111) et applications." Nice, 2003. http://www.theses.fr/2003NICE4075.
Full textThe work presented in this manuscript deals with the epitaxial growth of gallium nitride on silicon (111) substrate by Metal-Organic Vapor Phase Epitaxy for the optoelectronic applications of III-nitride semiconductors. Cracking of the GaN layers is a consequence of th tensile biaxial stress arising from the epitaxy on silicon. Experimental and theoretical analysis of the thermal and intrinsic stresses give a nes possibilities for the growth of GaN on S1 (111) and a better understanding of the problem of cracks in GaN layers. AIN/GaN superlattices have been used for stress engineering in GaN layers deposited on silicon and to strongly increase the GaN thickness deposited on Si (111) without any crack. InGan on silicon for electronic and optoelectronic applications. Three-dimensional growth process and Epitaxial Lateral Overgrowth (ELO) process have been developed in order to increase the optical and crystalline properties of GaN layers on silicon. For the first time, a decrease of the dislocations density of more than two orders of magnitude has been achieved in fully coalesced layers. The stresses present in ELO layers and cracked layers were explained by theoretical models for the reduction of stress from free surfaces. In agreement with these models, the stress present in GaN on silicon can be relieved and the formation of crack can be avoided by the decrease of the lateral dimensions of the layers
Luong, Thi kim phuong. "Croissance épitaxiale du germanium contraint en tension et fortement dopé de type n pour des applications en optoélectronique intégrée sur silicium." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4002.
Full textSilicon (Si) and germanium (Ge) are the main materials used as active layers in microelectronic devices. However, due to their indirect band gap, they are not suitable for the fabrication of light emitting devices, such as lasers or electroluminescent diodes. Compared to Si, pure Ge displays unique optical properties, its direct bandgap is only 140 meV above the indirect one. As Ge has a thermal expansion coefficient twice larger than that of Si, tensile strain can be induced in the Ge layers when growing Ge on Si at high temperatures and subsequent cooling down to room temperature. However, due to the existence of a misfit as high as 4.2 % between two materials, the Ge growth on Si proceeds via the Stranski-Krastanov mode and the epitaxial Ge films exhibits a rough surface and a high density of dislocations. We have evidenced the existence of a narrow substrate temperature window, allowing suppressing the three-dimensional growth of Ge on Si. By combining high-temperature growth with cyclic annealing, we obtained a tensile strain up to 0.30 %. The n-doping in Ge was carried out using the decomposition of GaP to produce the P2 molecules, which have a higher sticking coefficient than the P4 molecules. In particular, by implementing a co-doping technique using phosphorus and antimony, we have evidenced an intensity enhancement of about 150 times of the Ge direct band gap emission. This result represents as one of the best results obtained up to now
Gaillard, Philippe. "Modélisation de la croissance de boîtes quantiques sous contrainte élastique." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4303/document.
Full textThe growth and morphology of quantum dots is currently a popular subject as these structures have numerous potential uses, specifically in microelectronics and optoelectronics. Control of the size, shape and distribution of these dots is of critical importance for the uses that are being considered. This thesis presents a theoretical and numerical study of the growth of islands during molecular beam epitaxy. In order to study these dots, we used two models : a nonlinear study of an Asaro-Tiller-Grinfeld like instability, and kinetic Monte Carlo simulations. The first model is appropriate for low misfit systems, and is detailed in the case where misfit is anisotropic (this is the case when depositing GaN on AlGaN). In this case we took into account elastic effects, wetting effects and evaporation. Numerical calculations show faster growth, compared to the isotropic misfit case, and the growth of strongly anisotropic islands.The second model is based on kinetic Monte Carlo simulations that can describe 3D island nucleation. We use these simulations to study systems with high misfits, specifically Ge on Si. Adatom diffusion on a surface is considered and takes into account elastic effects, and surface energy anisotropy, that allows us to stabilize (105) facets. Simulation results show the growth of pyramid-shaped 3D islands, as observed in experiments, and their ripening is interrupted. The results of these simulations are then compared to the case of 2D nucleation, and we find that several of the known 2D properties also apply to 3D islands. Specifically, island density depends on a power law of D/F, the diffusion coefficient divided by the deposition flux
Joblot, Sylvain. "Croissance d'hétérostructures à bases GaN sur substrat de silicium orienté (001) : application aux transistors à haute mobilité d'électrons." Nice, 2007. http://www.theses.fr/2007NICE4102.
Full textGaN based devices are usually grown on silicon carbide (SiC), sapphire (Al2O3), and silicon substrates. Silicon substrate presents a thermal conductivity close to GaN one and advantages in terms of availability, size and cost. The (111) orientation with a 6-fold symmetry is preferred for the GaN-based heterostructures on silicon substrate. Nevertheless, in the aim of integrating GaN based devices into MOS (Metal-Oxyde-Semiconductor) based technology, the use of (001) and (110) orientations, with a square and quadratic surface symmetry, respectively, is preferred. This is why, in this thesis, we have developed the growth process of (Al,Ga)N structures on the (001) orientation. We have shown that the use of misoriented substrates towards the [110] direction with specific surface treatment and growth process have permitted to obtain a single orientation wurtzite GaN layers. They were grown by molecular beam epitaxy (MBE) and metal organic vapour phase epitaxy (MOVPE). We have also achieved, by the insertion of optimized AlN/GaN stack layers, crack-free AlGaN/GaN HEMT structures and devices with properties close to those obtained on the (111) orientation
Buchheit, Marc. "Application de l'imagerie de photoluminescence à l'étude de la distribution spatiale de propriétés physico-chimiques de semiconducteurs pour la réalisation de dispositifs." Ecully, Ecole centrale de Lyon, 1998. http://www.theses.fr/1998ECDL0042.
Full textMlayah, Adnen. "Etude par spectrométrie Raman des contraintes, dopage et défauts associés dans GaAs hétéroépitaxie." Toulouse 3, 1991. http://www.theses.fr/1991TOU30026.
Full textGodefroy, Anne. "Croissance et étude d'hétérostructures contraintes pour amplificateurs optiques insensibles à la polarisation." Rennes 1, 1994. http://www.theses.fr/1994REN1A001.
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