Tesis doctoral de Patricia Abellan Baeza
A variety of oxide materials properties are controlled by epitaxial strain due to lattice mismatch to the substrate and by interfaces structure and chemistry. Recent relevant examples span from layered heteroepitaxial systems exhibiting ionic conductivity [1], vertically assembled multifunctional nanostructures [2, 3] to superconducting nanocomposite films [4]. Therefore, the atomic-scale study of interfaces and the investigation of the strain state of thin films and nanostructures are crucial in exploring the structure-function correlations. the challenge of studying the microstructure at the interface between two materials is typically addressed by electron microscopy. Direct exploration of interfaces is possible in a transmission electron microscope (tem) by means of cross-sectional investigations. The improved experimental resolution and signal-to-noise ratio in images due to advances on spherical aberration correction enables more accurate image interpretation at subnanometer scale resolution. As an example, the spherical aberration corrected microscope at cemes, toulouse, used in this thesis, allows to measure deformations at the nanoscale by the geometrical phase analysis (gpa) technique [5] from high-resolution tem (hrtem) images to an accuracy of less than 1pm [6, 7]. Structural information at a larger scale and local chemical information may also be gained in the tem using different imaging modes and various spectroscopies. the microstructure of the systems under study is strongly dependent on the deposition process employed and on the particular processing conditions. While only one chapter of this report deals with high-temperature superconductors (hts), the choice of the deposition process used for the growth of all the different films and nanostructured templates reported here comes from previous research performed on deposition methods for hts wire technology. In other words, the synthesis of the samples studied for completion of this work has strongly benefited from the advances for the development of epitaxially deposited yba2cu3o7 superconducting films and associated buffer layers during the last years [8, 9]. Epitaxial thin films and lower dimension structures explored in this thesis were grown by metal-organic decomposition (mod), being capable of homogeneously covering large areas of material with relatively low cost. Thus, results obtained with this technique gather high potential to be ultimately used in power industry [10]. However, despite this added value, there are few specialists focused on the study of the microstructure of solution-derived systems. for this thesis, a variety of nanostructured functional oxide systems grown by colleagues of this research group by mod have been investigated using tem. This work is aimed to investigate the microstructural mechanisms acting at interfaces between multiple solution-derived materials and their strain state. A further goal is to investigate the dependence of the microstructure on processing conditions and the correlation between microstructure and specific properties of the different nanostructured systems. A motivation for this thesis was that the exploration of the microstructure of various solution-derived nanostructured systems and their evolution under specific processing conditions may lead to advances on the preparation of novel functional materials based on interface control. The materials explored during this thesis and reported in the experimental part of this manuscript are: superconducting yba2cu3o7 thin films grown on a bazro3 nanodot templates on (001) laalo3 substrates, different self-nanostructured la0.7sr0.3mno3 thin films grown on (001) srtio3, and self-assembled la0.7sr0.3mno3 nanodots on (001) mgo substrates. These systems display a strain state and interface structure which is observed to strongly affect their performance. Particularly, differences in the superconducting properties for the case of the nanostructured yba2cu3o7 thin films and on the magnetotransport properties for the case of segregated la0.7sr0.3mno3 thin films and nanodots are observed to be correlated to microstructure. The present thesis reviews the investigation performed on these systems. bibliography [1] j. Garcia-barriocanal, a. Rivera-calzada, m. Varela, z. Sefriouri, e. Iborra, c. Leon, s.J. Pennycook, j. Santamaria, science 321 (2008) 676 [2] j.L. Macmanus-driscoll, p. Zerrer, h. Wang, h. Yang, j. Yoon, a. Fouched, r. Yu, m.G. Blamire,q.X. Jia, nat. Mater. 7 (2008) 314 [3] h. Zheng, j. Wang, s.E. Lofland, z. Ma, l. Mohaddes-ardabili, t. Zhao, l. Salamanca-riba, s.R. Shinde, s.B. Ogate, d. Viehland, y. Jia, d.G. Schlom, m. Wutting, a. Roytburd, r. Ramesh, science 303 (2004) 661 [4] j. Gutierrez, a. Llordes, j. Gazquez, m. Gibert, n. Roma, s. Ricart, a. Pomar, f. Sandiumenge, n. Mestres, t. Puig, x. Obradors, nat. Mater. 6 (2007) 367 [5] m. J. Hí¿tch, e. Snoeck, r. Kilaas, ultramicroscopy 74 (1998) 131 hhtp://www.Hremresearch.Com [6] m. J. Hí¿tch, f. Houdellier, microelectronic engineering 84 (2007) 460 [7] f. Houdellier, m. Hí¿tch, f. Hí¼e, e. Snoeck in: advances in imaging and electron physics, chapter 6, aberration correction with the sactem-toulouse: from imaging to diffraction, 153 (2008) 225-259 [8] x. Obradors et al., Supercond. Sci. Technol. 19 (2006) s13 [9] d. Wesolowski, m. Yoshizumi, m.J. Cima: metalorganic deposition for htsc conductors, in flux pinning and ac loss studies on ybco coated conductors, m.P. Paranthaman, v. Selvamanickam (eds.) Nova science publishers, in. New york (2007) chapter 7 [10] f.F. Lange, science 273 (1996) 903
Datos académicos de la tesis doctoral «Interfacial structure and microstructural evolution of solution-derived dissimilar oxide nanostructures. implications on their functional properties«
- Título de la tesis: Interfacial structure and microstructural evolution of solution-derived dissimilar oxide nanostructures. implications on their functional properties
- Autor: Patricia Abellan Baeza
- Universidad: Autónoma de barcelona
- Fecha de lectura de la tesis: 23/05/2011
Dirección y tribunal
- Director de la tesis
- Felip Sandiumenge Ortiz
- Tribunal
- Presidente del tribunal: marie-josé Casanove
- jacques Rabier (vocal)
- (vocal)
- (vocal)