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Previous issue date: 2004-08-06 / Universidade Federal de Minas Gerais / This work reports a systematic study on the deposition and characterization of LaNiO3 thin
films. This material is a ceramic conductor and presents a near metallic behavior, and is interesting for capacitor electrodes application in memories systems, because of the reduction of fatigue behavior. The synthesis of the precursor resin was realized by the polymeric precursor method. The films were deposited with the spin-coating technique on five different substrates: Si(100), Safire(0001), MgO(100), LaAlO3(100) and SrTiO3(100), and after they were crystallized at 700ºC for two hours in a conventional furnace or at 700ºC for ten minutes in a microwave oven. After that, the films were characterized by X ray
diffraction, scanning electron microscopy, atomic force microscopy and measurements of electrical resistivity as a function of temperature. The films deposited on Si(100) were tested as electrodes for SrTiO3 capacitors, deposited with the same method. Polycrystalline and single phase LaNiO3 thin films were
obtained on Si(100), Safire(0001) and MgO(100) substrates, whereas the films deposited on LaAlO3(100) and SrTiO3(100) substrates were epitaxial. The method enable a good thickness control and allows the deposition of films without cracks and very homogeneous. Electrical measurements shown a metallic behavior between 20 and 300K, and the epitaxial films have a smaller
electrical resistivity, in comparison with the polycrystalline ones. The best result was obtained with the deposition on strontium titanate substrate and the measured resistivity was 250µΩcm, lower than that obtained with others
methods reported in the literature. The crystallization in a microwave oven was not so satisfactory, since films with higher resistivity than that crystallized in
conventional furnaces were obtained, because their morphology. However, these films are still good for an application in capacitors systems. The system Au/SrTiO3/LaNiO3/Si(100) was also studied being the lanthanum nickelate a good electrode for this system. Dielectric constant of 250 at 10 kHz was obtained which is about the same reported in the literature for this system with Pt electrodes. Dielectric constant measurements as a function of the applied
potential of work shown an asymmetric behavior because the difference between the two electrodes of the capacitor. The charge imprisonment in the ceramic/electrode interface causes a reduction in the capacitance with applied potential. In this manner, a simple methodology for preparation of thin films was
used resulting in good characteristics and promising for application in DRAM systems. THIN FILMS DEPOSITED ON SINGLE CRYSTAL SUBSTRATES BY THE POLIMERIC PRECURSOR METHOD: This work
reports a systematic study on the deposition and characterization of LaNiO3 thin films. This material is a ceramic conductor and presents a near metallic behavior, and is interesting for capacitor electrodes application in memories
systems, because of the reduction of fatigue behavior. The synthesis of the precursor resin was realized by the polymeric precursor method. The films were deposited with the spin-coating technique on five different substrates: Si(100),
Safire(0001), MgO(100), LaAlO3(100) and SrTiO3(100), and after they were crystallized at 700ºC for two hours in a conventional furnace or at 700ºC for ten minutes in a microwave oven. After that, the films were characterized by X ray
diffraction, scanning electron microscopy, atomic force microscopy and measurements of electrical resistivity as a function of temperature. The films deposited on Si(100) were tested as electrodes for SrTiO3 capacitors, deposited with the same method. Polycrystalline and single phase LaNiO3 thin films were
obtained on Si(100), Safire(0001) and MgO(100) substrates, whereas the films deposited on LaAlO3(100) and SrTiO3(100) substrates were epitaxial. The method enable a good thickness control and allows the deposition of films without cracks and very homogeneous. Electrical measurements shown a metallic behavior between 20 and 300K, and the epitaxial films have a smaller
electrical resistivity, in comparison with the polycrystalline ones. The best result was obtained with the deposition on strontium titanate substrate and the measured resistivity was 250µΩcm, lower than that obtained with others
methods reported in the literature. The crystallization in a microwave oven was
not so satisfactory, since films with higher resistivity than that crystallized in
conventional furnaces were obtained, because their morphology. However, these films are still good for an application in capacitors systems. The system Au/SrTiO3/LaNiO3/Si(100) was also studied being the lanthanum nickelate a
good electrode for this system. Dielectric constant of 250 at 10 kHz was obtained which is about the same reported in the literature for this system with Pt electrodes. Dielectric constant measurements as a function of the applied potential of work shown an asymmetric behavior because the difference between
the two electrodes of the capacitor. The charge imprisonment in the ceramic/electrode interface causes a reduction in the capacitance with applied potential. In this manner, a simple methodology for preparation of thin films was
used resulting in good characteristics and promising for application in DRAM systems. / Este trabalho apresenta um estudo sistemático sobre a deposição e caracterização de filmes finos de LaNiO3. Este material é um condutor cerâmico e apresenta um comportamento próximo ao metálico, sendo interessante para aplicações como eletrodos para capacitores em dispositivos de memória, promovendo a diminuição da fadiga nestes sistemas. A síntese da resina precursora foi realizada a partir do método dos precursores
poliméricos. Os filmes foram depositados pela técnica de spin-coating sobre cinco diferentes substratos monocristalinos: Si(100), safira(0001), MgO(100), LaAlO3(100) e SrTiO3(100), e depois foram cristalizados a 700ºC por duas horas em forno convencional ou a 700ºC por dez minutos em forno de microondas. Em seguida, foram caracterizados por difratometria de raios X, microscopia eletrônica de varredura, microscopia de força atômica e medidas de resistividade
como função da temperatura pelo método das quatro pontas. Os filmes depositados sobre Si(100) foram também testados como eletrodos em
capacitores de filmes finos de SrTiO3 obtidos pelo mesmo método. Foram obtidos sistemas monofásicos policristalinos quando depositados sobre Si(100), safira(0001) e MgO(100), enquanto que para filmes depositados sobre LaAlO3(100) e SrTiO3(100) a cristalização se mostrou epitaxial. O método possibilitou um bom controle na espessura dos filmes e produziu filmes com microestrutura sem trincas e bastante homogênea. As medidas de resistividade elétrica mostraram o comportamento metálico dos filmes no intervalo de 20 a 300K, sendo que os filmes epitaxiais têm valores menores de resistência que os filmes policristalinos. O melhor resultado foi obtido com a deposição sobre
titanato de estrôncio monocristalino, com valor de resistividade de 250µΩcm, que é um valor menor que a maioria daqueles apresentados na literatura para o mesmo sistema depositado por outros métodos. A cristalização em forno de microondas não se mostrou tão satisfatória quanto a realizada em forno convencional, levando a filmes com maior resistividade devido à morfologia dos mesmos, porém, ainda uma resistividade que possibilita uma aplicação bem sucedida em capacitores. Também foi estudado o sistema Au/SrTiO3/LaNiO3/Si(100); o niquelato de lantânio se mostrou um bom eletrodo
para o sistema em questão, obtendo-se um valor de constante dielétrica por volta de 250 em freqüências da ordem de kHz, semelhante ao obtido com eletrodos de platina. A medida de constante dielétrica como função do potencial de trabalho
mostrou um comportamento assimétrico devido à diferença entre os eletrodos do capacitor formado; o aprisionamento de cargas no eletrodo cerâmico causa uma diminuição da capacitância em certos potenciais. Assim, utilizou-se uma metodologia simples que resultou em filmes com boas características e promissores na aplicação em sistemas de memória do tipo DRAM.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufscar.br:ufscar/6491 |
| Date | 06 August 2004 |
| Creators | Mambrini, Giovanni Pimenta |
| Contributors | Varela, José Arana |
| Publisher | Universidade Federal de São Carlos, Programa de Pós-graduação em Química, UFSCar, BR |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFSCAR, instname:Universidade Federal de São Carlos, instacron:UFSCAR |
| Rights | info:eu-repo/semantics/openAccess |
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