Solid State Phenomena Vol. 105

Abstract: Control of the texture and the biaxial alignment of sputter deposited films has provoked a great deal of interest due to its technological importance. Indeed, many physical properties of thin films are influenced by the biaxial alignment. In this context, extensive research has been established to understand the growth mechanism of biaxially aligned Yttria Stabilized Zirconia (YSZ) as a buffer layer for high temperature superconducting copper oxides. In this work, the growth mechanism in general and the mechanism responsible of the biaxial alignment in detail were investigated for thin films of YSZ and TiN deposited by unbalanced magnetron sputtering using non-aligned polycrystalline stainless steel substrates. The mechanism responsible for the preferential out-of-plane alignment has been investigated by performing depositions on a non-tilted substrate. However, to study the in-plane alignment a tilted substrate was used. The microstructure of the deposited layers was characterised by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The crystallographic alignment has been investigated by X-ray diffraction (XRD) (angular scans and pole figures) and by Selective Area Diffraction (SAD). It was observed that the deposited layers show a zone T or zone II structure and the layers with a zone T structure consist of faceted grains. There seems to be a correlation between the crystal habit of these faceted grains and the measured biaxial alignment. A model for the preferential out-ofplane orientation, the in-plane alignment and the correlation between the microstructure and the biaxial alignment is proposed.

Abstract: High critical current density Jc under high magnetic field is required in numerous applications for high temperature superconductor YBa2Cu3O7-δ (Y123). Significant efforts have been made to control sample preparation in view of optimized textures and microstructures. In YBa2Cu3O7-δ superconductor, Jc is limited by grain misalignment and by other defaults like secondary phase (Y211), microcracks... So YBaCuO films were prepared by electrophoretic deposition directly on polycrystalline Ag substrate. Melt textured growth (MTG) in low oxygen partial pressure and cold rolling were performed to YBaCuO samples respectively to improve texture growth of the films and to study deformation effect on the texture. The film obtained by melted growth after rolling has better texture orientation than the film without rolling, and presents higher critical current density.

Abstract: Issues of ferroelectric high-density memories (>64Mb) indispensable for upcoming ubiquitous era have been on the cell integration less than 0.1um2 and reliabilities. Thus nanoscale control of microstructures of ferroelectric films with large switching polarization has been one of the issues to obtain the uniform electrical properties for realization of high-density memories. In this study the grain orientations and distributions of BT-based films by spin-on coatings were examined by EBSD (electron backscatter diffraction) technique. Ferroelectric domain characteristics by PFM (piezo-response force microscope) were also performed to study the dependence of reliabilities on the grain orientations and distributions. It is believed that understandings of the nucleation and growth mechanisms of the a- or b-axis oriented films during the thermal processes such as RTA and furnace annealing affecting on grain orientation and uniformity could be possible based on this experimental results.

Abstract: Tensile testing of thin rolled copper foils with thickness ranging from 10 to 250 µm shows a dependence of the fracture strain with respect to the thickness of the foils [G. Simons et al., in Solid Mechanics and its Applications, Vol. 114 (2004), pp. 89-96]. To understand the influence of the microstructure in the foils on this phenomenon the microtexture is investigated by orientation mapping through electron backscatter diffraction (EBSD). As the samples are rather small standard preparation techniques do not apply. Two methods are described which allow the investigation of different section cuts of the samples: Cross sections of the samples were produced by ion beam cutting with a wide beam of 7 keV Kr ions. Internal planes parallel to the specimen surface were made accessible by wet etching. The as-received material possesses a very strong texture consisting mostly of the cube component and some remnants of a previous rolling texture. Specimens tested in a tensile test do not show major microstructural changes compared to virgin samples. After a heat treatment at 300°C the cube texture has significantly weakened in favour of revived rolling components, and the fracture strain increased about ten times relative to the as-is material.