Metal-containing polymer thin films are known to possess interesting electrical, magnetic, optical or barrier properties. Such coatings can be deposited by plasma assisted chemical vapour deposition (PACVD). This technique comprises the fragmentation and rearrangement of metallorganic precursors within a low pressure non-equilibrium electrical discharge. In this work, the deposition of titanium containing species embedded into a polymeric network from titanium tetraisopropoxide (TiTP), Ti[OCH(CH(_3))(_2)](_4), and tetrakis (dimethylamido) titanium (TMT), Ti[N(CH(_3))(_2)](_4), precursors has been investigated as a function of glow discharge power and substrate location. In addition these precursors have been mixed with hydrogen and ammonia gases during PACVD. These metal-containing plasma polymers layers have been characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscopy (AFM).It has been demonstrated that Ti02/polymer composite layers can be produced using the TiTP precursor with a wide range of stoichiometries. The mixing of hydrogen gas with TiTP create films which are stable towards oxidation and aging. TiTP/ammonia mixtures produced Ti(0,N)/polymer films which contained Ti-N bonds. Injection of TMT into a glow discharge has been found to result in a non-thermally assisted intramolecular alkyl (3-hydrogen activation mechanism to produce Ti(0,C,N)/polymer composite films. The film composition is found to be independent of glow discharge power beyond 5 W. Mixing with hydrogen gas lowers the carbon content due to recombination reactions competing with plasma polymerization. TMT/ammonia mixtures result in a gas phase transamination reaction prior to and during plasma activation causing a drop in the total carbon content due to replacement of the -N(CH(_3))(_2) ligand by –NH(_x).

O objetivo deste trabalho foi contribuir para o desenvolvimento de um dispositivo elétrico baseado em moléculas organometálicas sobre substratos de silício poroso visando a sua aplicação no desenvolvimento de sensores de gás. Foi proposto um procedimento de deposição de monocamadas de moléculas de Ftalocianina sobre a superfície da estrutura de silício poroso aproveitando sua elevada superfície específica. As moléculas de Ftalocianina adsorvidas sobre o filme de silício poroso oxidado termicamente não apresentaram processos de reação química preservando suas características elétricas e ópticas. Foi fabricado um dispositivo com eletrodo de Ouro baseado no filme de moléculas de Ftalocianina depositado sobre silício poroso oxidado. A partir das curvas características I x V foi identificado o mecanismo de transporte de portadores através do filme de Ftalocianina e o tipo de junção na região de eletrodo-Ftalocinina. O mecanismo é baseado na corrente limitada por cargas armadilhadas nos níveis altamente localizados no interior da banda proibida entre os níveis HOMO e LUMO das moléculas de Ftalocianina. A resposta I x V do dispositivo mostrou-se sensível à exposição a gases orgânicos mostrando maior sensibilidade para o gás (Metanol) com maior constante dielétrica, sugerindo uma importante contribuição do efeito de blindagem sobre os níveis de armadilha, e como conseqüência a diminuição da profundidade destes níveis. / The aim of this work was to contribute for the development of an electrical device based on organometallic molecules onto porous silicon bulks for the application in the development of gas sensor devices. It was proposed a procedure of deposition of monolayer of Phthalocyanine molecules onto the surface of the porous silicon structure taking advantage of its high specific surface. The Phthalocyanine molecules adsorbed on the porous silicon film thermally oxidized did not show any chemical reaction process preserving their electrical and optical characteristics. A device was fabricated with Gold electrodes based on the Phthalocyanine molecules film deposited onto oxidized porous silicon. From the (I x V) characteristic curves, the carrier transport mechanism through the Phthalocyanine film and the junction type in the Phthalocyanine-electrode region were identified. The mechanism is based on the current limited by the trapped charges in the highly localized levels inside the band gap between the HOMO and LUMO levels of the Phthalocyanine molecules. The I x V response of the device showed to be sensitive to organic gases exposition showing higher sensibility to (Methanol) gas with higher dielectric constant, suggesting an important contribution of the shield effect on the trap levels and as a result decreasing the depth of these levels.

O objetivo deste trabalho foi contribuir para o desenvolvimento de um dispositivo elétrico baseado em moléculas organometálicas sobre substratos de silício poroso visando a sua aplicação no desenvolvimento de sensores de gás. Foi proposto um procedimento de deposição de monocamadas de moléculas de Ftalocianina sobre a superfície da estrutura de silício poroso aproveitando sua elevada superfície específica. As moléculas de Ftalocianina adsorvidas sobre o filme de silício poroso oxidado termicamente não apresentaram processos de reação química preservando suas características elétricas e ópticas. Foi fabricado um dispositivo com eletrodo de Ouro baseado no filme de moléculas de Ftalocianina depositado sobre silício poroso oxidado. A partir das curvas características I x V foi identificado o mecanismo de transporte de portadores através do filme de Ftalocianina e o tipo de junção na região de eletrodo-Ftalocinina. O mecanismo é baseado na corrente limitada por cargas armadilhadas nos níveis altamente localizados no interior da banda proibida entre os níveis HOMO e LUMO das moléculas de Ftalocianina. A resposta I x V do dispositivo mostrou-se sensível à exposição a gases orgânicos mostrando maior sensibilidade para o gás (Metanol) com maior constante dielétrica, sugerindo uma importante contribuição do efeito de blindagem sobre os níveis de armadilha, e como conseqüência a diminuição da profundidade destes níveis. / The aim of this work was to contribute for the development of an electrical device based on organometallic molecules onto porous silicon bulks for the application in the development of gas sensor devices. It was proposed a procedure of deposition of monolayer of Phthalocyanine molecules onto the surface of the porous silicon structure taking advantage of its high specific surface. The Phthalocyanine molecules adsorbed on the porous silicon film thermally oxidized did not show any chemical reaction process preserving their electrical and optical characteristics. A device was fabricated with Gold electrodes based on the Phthalocyanine molecules film deposited onto oxidized porous silicon. From the (I x V) characteristic curves, the carrier transport mechanism through the Phthalocyanine film and the junction type in the Phthalocyanine-electrode region were identified. The mechanism is based on the current limited by the trapped charges in the highly localized levels inside the band gap between the HOMO and LUMO levels of the Phthalocyanine molecules. The I x V response of the device showed to be sensitive to organic gases exposition showing higher sensibility to (Methanol) gas with higher dielectric constant, suggesting an important contribution of the shield effect on the trap levels and as a result decreasing the depth of these levels.

The research in the area of metal-organic frameworks (MOFs) continues to be interesting for their unique structures and tunable properties. In this thesis, the various aspects of metal-organic frameworks (MOFs) compounds are presented. As part of this study, preparation of MOFs of transition metals (Mn, Co, Ni, Zn), rare-earth metals (Y, La, Pr, Nd, Gd, Dy) and mixed metals (3d-4f) using aromatic carboxylates as linker ligands were accomplished. Structures of the synthesized compounds have been determined by single crystal X-ray diffraction technique. Magnetic properties of the transition metal based compounds have been studied by SQUID magnetometer and the magnetic behaviors have been correlated with their structures using suitable theoretical model. Photocatalytic properties on transition metal and mixed metal compounds have been investigated. Ligand-sensitized metal-center emission has been studied on the Eu3+ and Tb3+ doped MOF compounds of La and Y. Up-conversion luminescence properties of Nd based compounds have also been studied. To gain an insight into the possible mechanism of the formation of MOF compounds, a detailed study of the role of temperature and time during the synthesis has been undertaken. In addition, the transformations of low-dimensional structures to structures of higher dimensionality was also studied, both in the solid state as well as in the solution mediated processes. In Chapter 1 of the thesis an overview of framework compounds is presented. In Chapter 2, the synthesis, structure and magnetic properties of benzene tricaboxylate and 4,4’-oxybis(benzoate) compounds of 3d metals are presented. Some of these compounds show unusual structure and interesting magnetic properties. For example, three-dimensional MOF with -Mn-O-Mn- Kagome layer exhibits canted antiferromagntic behavior. Three-dimensional MOF based on body centered arrangement of Co4 clusters shows two-dimensional ferromagnetic behavior. In Chapter 3, the role of temperature and time of reaction in the formation of MOF compounds and the transformation studies are presented. These studies give a clue regarding the mechanism for the synthesis of MOF compound. In chapter 4, synthesis, structure and luminescent properties of rare-earth and 3d-4f mixed metal compounds are presented. The thermal decomposition of Gd-Co-pyridine carboxylate indicates the formation of nano-sized perovskite oxide at temperature ~ 700 °C. In chapter 5, the photocatalytic behavior for the decomposition of organic dyes using MOF compounds are presented.