Synthèse, caractérisation et évaluation de nouveaux précurseurs azotés pour dépôt de films d'oxydes métalliques MO2 (M = Hf, Zr) par MOCVD à injection liquide

De nouveaux précurseurs pour LI-MOCVD (Liquid injection Metal Organic Chemical Vapor Deposition) de Hf et de Zr ont été synthétisés et caractérisés par IR-TF, RMN multinoyaux, diffraction des RX sur monocristal et par ATG. La comparaison des comportements thermiques de différents complexes synthétisés a permis d'étudier l'effet de différents groupements sur leur volatilité et leur stabilité thermique. Les mono-amidinates et les monoguanidinates sont apparus plus volatiles et moins stables thermiquement que les di-amidinates et les di-guanidinates. Les films d'oxyde d'hafnium déposés ont été caractérisés par DRX, XRR, ATR et XPS. Les mono-guanidinates asymétriques tel que Hf(NEt2)3(iPr-Et2-tBu-GUA) et les di-guanidinates asymétriques tel que Hf(NMe2)2(Et-Me2-tBu-GUA)2 sont très prometteurs pour le dépôt de couches d'HfO2. Ils permettent la stabilisation d'une phase d'HfO2 de structure cristalline de symétrie supérieur à la phase monoclinique à 580C. De plus, ces précurseurs permettent l'obtention des films de HfO2 nitruré en absence d'une étape supplémentaire de nitrurationNew precursors for LI-MOCVD (Liquid Injection Metal Organic Chemical Vapor Deposition) of Hf and Zr were synthesized and characterized by FT-IR, NMR multi-nuclei, X-ray diffraction on monocrystal and TGA. The comparison of the thermal behaviours of various synthesized complexes made it possible to study the effect of various groups on their volatility and thermal stability. The mono-amidinates and -guanidinates appeared more volatile and less stable thermically than the di-amidinates and -guanidinates. The films of hafnium oxide deposited were characterized by XRD, XRR, ATR and XPS. The asymmetrical mono-guanidinates such as Hf(NEt2)3(iPr-Et2-tBu-GUA) and the asymmetrical diguanidinates such as Hf(NMe2)2(Et-Me2-tBu-GUA)2 are very promising for the deposit of HfO2 films. They allow the stabilization of a crystalline phase of HfO2 with a symmetry that is superior to the monoclinical phase at 580C. Moreover, these precursors allow obtain nitrided films of HfO2 in absence of an additional stage of nitridingLYON1-BU.Sciences (692662101) / SudocSudocFranceF

The structure and binding mode of citrate in the stabilization of gold nanoparticles

Elucidating the binding mode of carboxylate-containing ligands to gold nanoparticles (AuNPs) is crucial to understand their stabilizing role. A detailed picture of the three-dimensional structure and coordination modes of citrate, acetate, succinate and glutarate to AuNPs is obtained by C-13 and Na-23 solid-state NMR in combination with computational modelling and electron microscopy. The binding between the carboxylates and the AuNP surface is found to occur in three different modes. These three modes are simultaneously present at low citrate to gold ratios, while a monocarboxylate monodentate (1 kappa O-1) mode is favoured at high citrate: gold ratios. The surface AuNP atoms are found to be predominantly in the zero oxidation state after citrate coordination, although trace amounts of Au delta+ are observed. Na-23 NMR experiments show that Na+ ions are present near the gold surface, indicating that carboxylate binding occurs as a 2e(-) L-type interaction for each oxygen atom involved. This approach has broad potential to probe the binding of a variety of ligands to metal nanoparticles