This research describes the development of ALD processes for the deposition of nitride materials including tantalum, hafnium and gadolinium nitrides. Ta and Hf nitrides are of significant interests for sub-l00nm silicon based electronic devices, while Gd nitride may be exploitable in future spintronic devices. ALD has been established a key manufacturing tool in microelectronics, the development of ALD processes for these nitrides are essential for future manufacturing of electronic devices and can benefit future manufacturing of spintronic devices. In the current research, these nitrides were deposited using ALD and the films were characterised using MEIS, AES, XRD, TEM, SEM, AFM, and a four point probe. Ta nitride films were grown at temperatures ranging from 200°C to 375°C using ALD with Pentakis( dimethylamino )tantalum, Ta(NMe2)s as the metal source and either ammonia or monomethyl-hydrazine (MMH) as a nitrogen eo-reactant. Self-limiting behaviour was observed for both ammonia and MMH processes, with growth rates of 0.6 and 0.4 A/cycle respectively at 300°C. Films deposited using ammonia were found to have a mono-nitride stoichiometry with a cubic microstructure and resistivities as low as 70 mfz.cm. In contrast, films deposited using MMH were found to be nitrogen rich Ta3Ns with an amorphous microstructure and high resistivities (>4 O.cm). A QCM was used to measure mass gain and loss during the cyclic ALD processes and the data was used in combination with MEIS to elucidate the Ta(NMe2)s absorption mechanisms. For Hf nitride, films were firstly deposited using thermal ALD with tetrakis( dimethyl amino )hafnium, Hf(NMe2)4 and ammonia between 100 and 400°C. Self- limiting behaviour was observed, however, the films exhibit a low density and were prone to oxidation during post-deposition exposure to air. A comparison between thermal and PE ALD was then made at 300°C with tetrakis(ethylmethylamino)hafnium, Hf(NEtMe)4 as the metal source and either molecular or plasma-cracked ammonia as a nitrogen source. PEALD allows shorter purge time, which significantly reduces the cycle length; PEALD also results in higher film density. The densities of the films deposited by PEALD and thermal ALD were found to be 11.6 and 9.7 g/cm'' respectively. Mass spectroscopy indicates that the process characteristics in PEALD are attributed to the nature of the eo-reactants, namely, radicals of hydrogen and nitrogen. Their high reactivity and short life time are responsible for the resulted high density and the short required purge time. All films deposited were found to be insulators and with an amorphous microstructure. The films deposited by PEALD remain amorphous and stable with no interactions between Hf and Si after vacuum annealing up to 800°C. Gd nitride films were successfully deposited using a cyclic PEALD based process. The deposition was carried out with tris(methylcyclopentadienyl)gadolinium, Od(MeCp )3, and remote nitrogen plasma exposure, separated by argon pulses. Films were deposited at temperatures between 150 and 300°C and capped with Ta nitride to prevent post deposition oxidation. Gd nitride with a 1:1 Od:N ratio, low oxygen incorporation (5%), good thickness uniformity (95%), an amorphous microstructure and smooth surface (Ra.=~0.7nm) have been deposited. Deposition with tris(silylamide)gadolinium, Od{N(SiMe3hh, and either ammonia or MMH was also investigated. Although the process using ammonia was unsuccessful due to the insufficient reactivity of ammonia, the results show that a reaction between Od{N(SiMe3)2h and MMh does take place. Od{N(SiMe3)2h was found to be a self-limiting precursor, however, the as deposited films were found to be OdSixOy• The silicon incorporation was attributed to partial breakdown of silylamine groups, where the oxygen incorporation was attributed to the possible tetrahydrofuran (THF) contamination in the precursor.

In the solid state the rotation of a methyl group is hindered by a potential barrier and at low temperature the rotational motion is characterised by quantum tunnelling. The Pauli Exclusion Principle imposes constraints on the allowable eigenstates of the methyl rotor and leads to a combination of spatial and spin variables. The characteristics of these quantum tunnelling states, labelled A and E, are explored experimentally and methods are investigated for creating prescribed non-equilibrium states. We will investigate and explore the tunnelling polarization associated with the A and E tunnelling-magnetic levels by means of field-cycling NMR. Secondary rf irradiation is used to drive A-E and E-A transitions associated with NMR tunnelling sidebands. This polarization is then transferred to the 1H Zeeman system at a field-dependent level-crossing where the methyl tunnelling frequency equals one or two times the 1H Larmor frequency. The level-crossing contact is a necessary step since the tunnel temperature cannot be measured directly with a pulse. A new pulse sequence is described and the resulting spectra are analogous to the solid effect and dynamic nuclear polarization. Therefore we assign the phrase ‘dynamic tunnelling polarization’ to describe the experiments. Two samples are studied in depth, methyl ethyl ketone and acetophenone which have tunnel frequencies of 495 and 1435 kHz respectively. The experiments investigate the phenomena as a function of a variety of physical parameters in order to determine the fundamental physics.

Ce travail porte sur la synthèse et la caractérisation d’oxydes de manganèse de formule généraleCaxMnyOz avec y/x > 1. Par une approche de chimie du solide, les propriétés redox de ces matériauxseront corrélées à leur composition chimique et leur structure cristalline ce qui constitue une étude enamont de l’application pour ces systèmes pouvant jouer le rôle de tampon à oxygène dans desprocessus catalytiques. Les composés ont été synthétisés par autocombustion en voie aqueuse etcaractérisés d’un point de vue structural. Les propriétés redox ont été évaluées par ATG et lespropriétés de réductibilité par H2-TPR pour certains composés. Quelles que soient la structure, ladimensionnalité ou la valence du manganèse dans les composés oxydés (Mn4+/Mn3+), le manganèsese réduit totalement en Mn2+ sous atmosphère réductrice (Ar/H2). Les composés réduits cristallisentdans une solution solide de type NaCl de formule Ca1-xMnxO. Les mécanismes de réduction dumanganèse au sein de ces structures ont été appréhendés sur la base des analysesthermogravimétriques. Afin de faire varier les températures de réduction, l’iono-covalence de la liaisonMn-O a été modifiée via des substitutions cationiques (i) sur les sites du calcium principalement ausein de réseaux 2D ou (ii) sur les sites du manganèse essentiellement dans les réseaux 3D avec laprésence d’Al3+ ou de Fe3+ de rayons ioniques comparables respectivement à Mn4+ et Mn3+. Lessolutions solides ont été caractérisées d’un point de vue structural mais aussi pour leurs propriétésredox. Il convient de souligner que les phases substituées au Fer présentent des propriétés redox toutà fait remarquables dans la mesure où les ions Fe3+ tout comme Mn4+/3+ se réduisent d’abord en Fe2+puis en Fe° qui est dès lors expulsé hors de la matrice oxyde. Lors de la réoxydation, le fer réintègrele réseau 3D et les matériaux sont cyclables dans des conditions réductrices puis oxydantes à l’air àdes températures inférieures à 1000°C. / This work deals with the synthesis and characterization of manganese oxides with CaxMnyOz formulaand y/x >1. According to a solid state chemistry scope, the redox properties of these materials will becorrelated to their chemical composition and crystallographic structure which constitutes a forehandexploratory study of compounds that are intended to be used for the automotive catalysis exhaustbased on the three-way catalysis principle. The materials were synthesized by aqueous selfcombustionroute and structurally characterized. Redox properties and reducibility properties wereevaluated by TGA and H2-TPR, respectively. Whatever the structure, the dimensionality of the networkor the manganese valence in the starting oxidized material, all of the manganese ions are completelyreduced (Mn2+) in a Ar/H2 atmosphere. The reduced compounds crystallize in a rock-salt type solidsolution with the formula Ca1-xMnxO. The mechanisms of manganese reduction within these structureswere explored on the basis of TGA analysis. In order to tune the reduction temperatures, the ionocovalenceof the Mn-O bond has been modified by either cationic substitution of calcium in the 2Dnetworks or either substitution of manganese in the 3D networks. In this last case, Substituting ionswere Al3+ and Fe3+ which ionic radii comparable to Mn4+ and Mn3+, respectively. Solid solutions havebeen characterized from a structural point of view but also for their redox properties. One shouldnotice that iron substituted compounds exhibit remarkable redox properties because Fe3+ ions firstreduce in Fe2+ iron before a final reduction in Fe° that is consequently expulsed from the matrix. Atreoxidation, iron returns into the 3D network and cycling can be observed when reducing and oxidizingat temperatures lower than 1000°C.