Dissertationen zum Thema „Films minces épitaxiales“
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Passuti, Sara. „Electrοn crystallοgrathy οf nanοdοmains in functiοnal materials“. Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMC230.
Der volle Inhalt der QuelleThe investigation of functional materials has increasingly focused on samplescharacterized by nanodomains (ranging from submicron sizes to tens of nanometers) due totheir interesting physical properties, such as those observed in thin films and ceramic materials.When unknown phases need to be determined or detailed information on the crystallinestructure of these materials is required, this presents challenges for both X-ray diffraction andtransmission electron microscopy (TEM). To address this, a novel electron diffraction (ED) technique,Scanning Precession Electron Tomography (SPET), has been employed. SPET combinesthe established precession-assisted 3D ED data acquisition method (a.k.a. Precession ElectronDiffraction Tomography – PEDT) with a scan of the electron beam on a region of interest (ROI)of the specimen at each tilt step. This procedure allows to collect 3D ED data from multipleROIs with a single acquisition, facilitating structure solution and accurate structure refinementsof multiple nanodomains or distinct areas within a single domain, at once. In this thesis, thepotentialities of SPET are explored on both oxide thin films and ceramic thermoelectric materialsprepared as TEM lamellae. Additionally, a novel methodology was developed to efficientlyanalyze the large amount of data collected. This method involves sorting the diffraction patternsaccording to their region of origin, reconstructing the diffraction tilt series of the ROI, andautomatically processing the obtained tilt series for structure solution and accurate refinements.This work demonstrates the potential of SPET for the fine crystallographic characterization ofcomplex nanostructured materials. This approach appears to be complementary to what can bedone in imaging or spectroscopy by (S)TEM or, in diffraction, by the so-called 4D-STEM andACOM approaches
Madaci, Ismail. „Croissance épitaxiale de films minces de Fe3O4 sur ZnO par PLD : une perspective pour la spintronique“. Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPAST170.
Der volle Inhalt der QuelleThis PhD work is inscribed in the researchdomain of materials science for spin electronics. Weaim to master the epitaxial growth of the halfmetallic Fe3O4, a material with a fully polarizeddensity of states, on ZnO semiconducting substrates,possessing a long spin coherence length (within themicrometer range). The successful combination“Fe3O4/ZnO” is the first necessary foundation forphysical spin injection studies on devices. In this worknotable achievements were realized, particularly thesuccessful epitaxial growth processes for Fe3O4 onZnO(000±1) substrates, regardless of substratepolarity. Precise control of oxygen partial pressureduring deposition allowed the synthesis of purestoichiometric Fe3O4 thin films, with magnetizationproperties closely resembling those of bulk Fe3O4.The investigation provided critical insights into theinfluence of growth temperature on the interfacebetween Fe3O4 and ZnO, including the effects ofintentionally grown FeO template layers.Furthermore, the research extended to explore theimpact of substrate miscut on remanentmagnetization of Fe3O4 thin films. Utilizingadvanced transmission electron microscopytechniques, a comprehensive analysis of epitaxialgrowth revealed various structural defects,providing an in-depth understanding of thechallenges in this area of research
Bao, Zhaohui. „Croissance épitaxiale, caractérisation structurale et études magnétiques de couches minces d'UO2“. Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI102.
Der volle Inhalt der QuelleWe have investigated structural and magnetic properties of epitaxial UO2 andUO2/Fe3O4 thin films fabricated by reactive DC-sputtering. The UO2 layer grew commensurately on LaAlO3 substrate with epitaxial relationships of (001)UO2 Î (001)LAO and <100>UO2 Î <110>LAO. Due to the pseudomorphic growth which extended up to 45 Å, a strain (Á) of about 2% were introduced into the UO2 epilayer. A partial relaxation process was observed for films thicker than 500 Å. The large mosaic affects strongly the magnetic properties. Rosonant X-ray scattering studies revealed that the Néel temperature remained at 30.8 K. However, a small reduction of TN is expected at tuo2 ~ 50 Å. The second-order phase transition was found for films with thickness between 181 and 4500 Å. Using the Bernhoeft plot, the thickness of the magnetically ordered phase was estimated. The pseudomorphic part was magnetically inactive. The exchange bias studies confirmed this result. For the first time, the magnetocrystalline anisotropy constant of UO2 was found to be about 1 x 107 erg/cm3
Masset, Gauthier. „Croissance épitaxiale de films et superrésaux de vanadates de terres rares : vers l’émergence de propriétés multiferroïques“. Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0279.
Der volle Inhalt der QuelleRecently, a new origin for ferroelectricity has been discovered and studied in perovskite superlattices ABO₃/A'BO₃, (ABO₃ with A = rare earth or alkaline earth, B = 3d, 4d or 5d transition metal). This phenomenon, called improper hybrid ferroelectricity, rises considerable interest, since it may yield the emergence of a multiferroic or even magnetoelectric behavior in magnetic perovskites. Among the promising perovskite materials for such a ferroelectric and magnetoelectric behavior, rare earth vanadates (compounds RVO₃) have been identified. The thesis work reported in this manuscript aimed at studying RVO₃/R'VO₃ superlattices and their physical properties. The epitaxial growth of PrVO₃ and LaVO₃ thin films by ozone-assisted molecular beam epitaxy (MBE) is thoroughly investigated. An optimization of the growth process is carried out, mainly supported by in situ electron diffraction (RHEED), and ex situ X-ray diffraction (XRD). The epitaxy with layer-by-layer 2D growth mode for LaVO₃ and PrVO₃ on SrTiO₃(001) allows the deposition of high quality LaVO₃/PrVO₃ superlattices. The analysis by electrons microscopy (TEM) highlights abrupt interfaces and enables the determination of structural variants and atomic displacements, key elements for the emergence of improper hybrid ferroelectricity. The first results on the superlattices’ electric properties suggest the occurrence of a ferroelectric behavior in a (LaVO₃)₁/(PrVO₃)₁ superlattice
Lamirand, Anne. „Croissance épitaxiale, structure atomique et couplage d'échange de bicouches ultra-minces d'oxydes sur métaux“. Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY032/document.
Der volle Inhalt der QuelleThis thesis deals with the determination of atomic, electronic and magnetic structure of ferromagnetic and antiferromagnetic ultrathin layers to better understand the mechanism of the exchange coupling which could takes place at their interface. Exchange coupling, expression of the interaction between the two materials, manifests itself by a shift of hysteresis loop and an increase in coercivity below the blocking temperature. We have paid attention to the systems of CoO/FePt on Pt(001), CoO/Fe and CoO/Fe3O4 on Ag(001). We combined experimental techniques mainly using synchrotron light to characterize them. As a first step, we optimized in a ultra-high vacuum (UHV) environment the elaboration of the systems looking for an appropriate surface, the high control of growth conditions and the supervision of the structure by in situ X-ray surface diffraction. The crystalline structure was precisely then detailed. As a second step, we studied the magnetic structure and properties ex situ by X-ray magnetic circular and linear dichroïsm and magneto-optic Kerr effect. The relation between exchange coupling and interface structure is discussed all along the manuscript
Girardot, Cécile. „Structure et propriétés physiques de films minces RENiO3 (RE = Sm, Nd) élaborés par MOCVD“. Phd thesis, Grenoble INPG, 2009. http://www.theses.fr/2009INPG0058.
Der volle Inhalt der QuelleRare earth nickelates present both electric and magnetic phase transitions, whereof the critical temperatures can be tuned with the rare earth size. Using MOCVD, we have synthesized Sm1-xNdxNiO3 (0
Girardot, Cécile. „Structure et propriétés physiques de films minces RENiO3 (RE = Sm, Nd) élaborés par MOCVD“. Phd thesis, Grenoble INPG, 2009. http://tel.archives-ouvertes.fr/tel-00413590.
Der volle Inhalt der QuelleSpiesser, Aurélie. „Croissance épitaxiale et propriétés magnétiques d'hétérostructures de Mn5Ge3 sur Ge pour des applications en électronique de spin“. Thesis, Aix-Marseille 2, 2011. http://www.theses.fr/2011AIX22001/document.
Der volle Inhalt der QuelleSpin-electronics based on ferromagnetic metal/semiconductor systems offer a pathway toward integration of information storage and processing in a single material. This emerging fieldaims to create a new generation of electronic devices where two degrees of freedom will be associated: spin and charge of carriers. In this context, the outcome of this thesis is toelaborate a novel ferromagnetic compound, namely Mn5Ge3, on Ge using molecular beamepitaxy method. The interests in this compound are manyfold: it can be stabilized as a uniquephase on Ge(111) in the form of epitaxial thin films, it is ferromagnetic until room temperature and it is compatible with Si-based conventional microelectronics. In this work,one major effort was devoted to the epitaxial growth of Mn5Ge3 on Ge using Solid PhaseEpitaxy method. By combining structural and magnetic characterizations, we demonstrated high quality epitaxial thin Mn5Ge3 films with good magnetic properties. We also studied theeffect carbon incorporation on the structural and magnetic properties of epitaxial Mn5Ge3films. The carbon-doped films exhibit a high Curie temperature with an atomically smoothinterface and a high thermal stability. All these results show that Mn5Ge3 is a promisingcandidate opening up the ways for spin injection via tunnel effect through the Schottky barrierinto Ge
Waroquet, Anne. „Couches-minces dans le système K-Nb-O : croissance épitaxiale et nanostructuration par PLD de phases pérovskite, TTB et lamellaires“. Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S143/document.
Der volle Inhalt der QuelleThe purpose of this work was the elaboration by pulsed laser deposition (PLD) and the characterization of thin films of oxides in the K-Nb-O system, and more precisely that of a tetragonal tungsten bronze phase (TTB) as nanorods, of potential interest as a new lead free piezoelectric. In spite of a strong growth competition between the different phases, the detailed study of the deposition conditions showed that it is possible to obtain KNb3O8, K4Nb6O17, K6Nb10,88O30 (TTB ) and KNbO3 in thin films form after an important optimization step. We have determined the influence of these deposition conditions on the formation and the nanostructuration of these compounds as thin films. In particular, it was shown that the temperature and the PLD target’s composition has a strong influence on the growth of the TTB structure. A further study of these phases revealed that all have a specific morphology related to their anisotropic structure, that we have controlled by the epitaxial growth on the (100) and (110) SrTiO3 substrates. The existence of a piezoelectric activity in the TTB thin films, evidenced by PFM, gives a great interest to this phase. This TTB phase was also obtained in the Na-K-Nb-O system, well known for its piezoelectric and ferroelectric properties, opening the way to new research
Iliescu, Ionela. „Croissance, caractérisation et transformation de phase dans des couches minces d'YMnO3“. Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI018/document.
Der volle Inhalt der QuelleMultiferroic YMnO3 (YMO) films have been grown by MOCVD on (100)-oriented Si, STO, LAOand LSAT substrates. The effect of the film thickness and the chemical composition on structuraland magnetic properties has been investigated. YMO can crystallize in two structure: hexagonal(h-YMO) and orthorhombic (o-YMO), generally considered as stable and metastable phases,respectively. Both phases, together with their amorphous precursor phase, are studied in this thesis.On one side, a selective growth of the amorphous, o-YMO or h-YMO phase is achieved on Sisubstrates through the deposition conditions. An extensive study of the optimal conditions hasbeen carried out. An irreversible phase transformation from amorphous to crystalline o-YMOphase takes place at an almost constant temperature (~ 700 °C) and in a short period of time (~min). The o-YMO phase thus obtained is stable at least up to 900 °C.On the other side, the o-YMO phase is epitaxially stabilized on perovskite type substrates (STO,LAO, LSAT). The films on STO and LSAT substrates present mainly the (010) orientation whilethose on LAO substrate are (101)-oriented. Secondary domain orientation are observe in particularon STO substrates: (010) in plane with 90° rotation. Strained films are observed for smallthicknesses. The magnetic measurements show a spin glass behavior for either o- or h-YMO phase,independently of the substrate
Tillier, Jérémy. „Films Ni-Mn-Ga et mémoire de forme magnétique : Elaboration et caractérisation des propriétés structurales et magnétiques“. Phd thesis, Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00553096.
Der volle Inhalt der QuelleRuano, Merchán Catalina. „Synthesis and characterization of 2D complex oxide films in the SrTiO₃/Pt(111)/Al₂O₃(0001) system“. Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0039.
Der volle Inhalt der QuelleThe formation of 2D dodecagonal quasicrystalline oxides (OQC), as related approximant phases were recently reported in thin films derived from BaTiO₃ or SrTiO₃ perovskites deposited on (111)-oriented Pt single crystal. These 2D structures add novel functionalities to the ultra-thin films of ternary oxides supported on metals when approaching the 2D limit. Here, we use a thin film stacking approach in which the single crystal is replaced by a Pt (111) buffer layer, deposited by MBE on an Al₂O₃(0001) substrate. An ultra-thin film of SrTiO₃ was subsequently deposited by PLD. The film stacking is fully characterized by diffraction (LEED, RHEED, XRD),microscopy (STM, TEM, Nano-SAM) and spectroscopy (XPS, AES) techniques. We report the discovery of three OQC approximants obtained by reducing this system by annealing at high temperature under vacuum conditions. These phases can be described by three different tilings constructed with NGT elements. An atomic model determined by DFT, in agreement with the experimental observations, is proposed for each approximant. This thin-film approach can be useful for exploring the formation of complex 2D oxide phases in other metal-oxide combinations
Hamidi, Sakr Amer. „Thin films of polythiophenes oriented by epitaxy and high-temperature rubbing : correlations with optical, charge-transport and thermoelectrical properties“. Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAE019.
Der volle Inhalt der QuelleThe aim of this thesis is to study the effect of alignment and morphological control on polythiophene thin films and to correlate this control with the optical, charge transport and thermoelectric properties. Since semiconducting polymers are inherently anisotropic by nature, studying these polymers in the aligned state was essential to understand their properties. This study could be achieved by employing two techniques that are successful in orienting polymers in thin films. High-temperature rubbing (HTR) along with directional epitaxial crystallization (DEC) produced highly oriented polythiophene thin films with order parameters reaching 0.87 and crystallinities up to 65%. HTR was a successful method to control crystal sizes in rubbed poly(3-hexyl-thiophene) P3HT films. By this method, the equilibrium melting temperatures of other poly(3-alkyl-thiophene) P3ATs were calculated. We learned that the free excitonic bandwidth depends on the crystal dimensions in the rubbed thin films. We also learned that the planarity of tie-chains linking consecutive crystalline domains plays a very important role in field-effect mobility. We also discuss the peculiar morphology of poly(3-butyl-thiophene) (P3BT) and the role of the butyl side groups. Then DEC method was proposed to orient poly(3-dioctylphenyl-thiophene) (PDOPT) thin films. We examined the effect of molecular weight of PDOPT on the level of crystallinity and alignment. Consequently, this relation provided fundamental information that helped us refine the crystal structure of PDOPT. Finally, a versatile method to produce highly aligned conducting polymers was proposed. HTR followed by P-type doping proved to be an excellent way to produce highly aligned conducting thin films with enhanced thermoelectric properties. This thesis brings value to the importance of morphology control and the alignment of semiconducting thin films to understand the various properties of these highly anisotropic systems
Liakakos, Nikolaos. „Organometallic approach to the growth of metallic magnetic nanoparticles in solution and on substrates“. Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0026/document.
Der volle Inhalt der QuelleThis thesis concerns a new wet chemical seeded growth method that can produce arrays of metal nanostructures epitaxially grown on crystalline macroscopic surfaces which act as seeds. This approach produces wafer-scale organized 2D hexagonal arrays of perpendicularly oriented, monodisperse and monocrystalline metallic Co nanowires with diameters below 10 nm which exhibit perpendicular magnetic anisotropy and are interesting for applications in ultra high density magnetic recording. Extension of this approach to iron gives rise to nanostructured iron films. The orientation of the nanostructures on the solid substrate depends on the substrate crystallographic orientation, whereas their morphology is dictated by the solution composition. This objective was attained through parallel studies on the growth mechanism of cobalt nano-crystals in solution which revealed an unexpected influence of the stock solution preparation procedure on the nanocrystal morphology. In addition, the use of nanoscopicseeds for the overgrowth of cobalt and iron gave rise to long Co nanowires and Co-Fe dumbbells and contributed to the definition and the improvement of the experimental conditions for the seeded growth of Co and Fe on the solid substrates
Chamorro, Coral William. „Microstructure, chemistry and optical properties in ZnO and ZnO-Au nanocomposite thin films grown by DC-reactive magnetron co-sputtering“. Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0253/document.
Der volle Inhalt der QuelleComposite materials can exhibit properties that none of the individual components show. Moreover, composites at the nanoscale can present new properties compared to the bulk state or to macro-composites due to confinement and quantum size effects. The semiconductor/metal nanocomposites are highly interesting due to their unique catalytic and optoelectronic properties and the possibility to tune them easily. This PhD work gives insight into the specific interactions and resulting physical properties occurring in ZnO and ZnO-Au nanocomposite films grown by reactive DC magnetron sputtering. The results can be summarized in two points: First, it was possible to tune the microstructural and optical properties of ZnO. Epitaxial growth of ZnO onto sapphire was achieved for the first time in O2-rich conditions without thermal assistance. Also, a study of the optical properties highlights the close relationship between the bandgap energy (E_g ) and the defect chemistry in ZnO films. A model was proposed to explain the large scatter of the E_g values reported in the literature. Second, the deep influence of the incorporation of gold into the ZnO matrix on important material properties was revealed. Moreover, the presence of donor (acceptor) defects in the matrix is found to give rise to the reduction (oxidation) of the Au nanoparticles. This research work contributes to a better understanding of semiconductor/metal nanocomposites revealing the key role of the state of the semiconductor matrix
Benamara, Omar. „Croissance physique d'îlots de Pt et Co sur oxydes pour l'auto-organisation de nano-bâtonnets de Co élaborés par synthèse chimique“. Thesis, Toulouse, INSA, 2010. http://www.theses.fr/2010ISAT0032/document.
Der volle Inhalt der QuelleThe subject of this thesis is to be part of strategies in order to organize nanostructures, particularly strategies to increase information density in magnetic media. The synthesis techniques used in chemistry (LPCNO-INSA laboratory) is allowed to develop monocrystalline nanorods of cobalt whose ferromagnetic properties in terms of anisotropy and magnetization present a great interest for applications in the field of magnetic storage. The success in controling the growth of these nanorods arranged perpendicularly on a substrate can lead to achieve a high density media. We tested the perpendicular growth of monocrystalline nanorods of cobalt on a continuous and epitaxial layer of Pt (111) grown on a substrate of sapphire (Al2O3) and showed that this combination of two types of deposits (physical and chemical) give actually a dense and perpendicular network of Co nanorods. In the aim to organizing this growth and decoupling physically the nanorods we studied the growth of these Co nanorods on 3D metallic islands of Pt and Co. In the first part we studied the crystal structure, morphology, size distributions and the stress state of Pt and Co islands deposited on the surface (0001) of sapphire and (001) surface of MgO by sputtering. And in the second part, we studied the growth of Co nanorods on a Pt and Co islands mastered in the previous step