Papers by Eleonora Bellini
Journal of Physics D, Jul 2, 2013
We investigated the physical microstructure and the domain structure of a CoFeB layer 30 A and 14... more We investigated the physical microstructure and the domain structure of a CoFeB layer 30 A and 14 A thick, embedded in a multilayer composed of MgO (50 A)/CoFeB/MgO (15 A), by transmission electron microscopy and Lorentz microscopy. Structurally both films appeared similar and polycrystalline in character. However, the magnetization reversal behaviour observed during Lorentz microscopy experiments was found to vary considerably with the CoFeB thickness. Indeed, in the 14 A CoFeB layer we found an unusual asymmetric orientation of domain walls when varying the direction of the applied field. To assist in the interpretation of the experimental results, we carried out calculations using a modified Stoner–Wohlfarth model, including unidirectional anisotropy. A good agreement was found between measured and calculated domain wall orientations. To explain the presence of the unidirectional anisotropy, we propose the possibility of formation of an interfacial structure that can give rise to an exchange bias effect, which has been previously seen from other studies.
Thin Solid Films, Apr 1, 2014
Deposition and structural characterization of Sm x S y O z-based thin films are reported. The che... more Deposition and structural characterization of Sm x S y O z-based thin films are reported. The chemical synthesis of the Sm x S y O z compounds is performed by thermolysis of dithiocarbamate precursors, followed by the drop casting deposition of the synthesized material, and by the thermal treatment at different temperatures (250°C, 500°C and 900°C) and atmospheric conditions (nitrogen and air). Structural and morphological properties have been investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction, and were found to depend closely on the treatment conditions. In particular, the treatment at temperatures as high as 900°C and in a nitrogen atmosphere enhances the crystalline nature of the films and increases the samarium content in comparison to the oxygen content. Therefore, the temperature of 900°C and the nitrogen atmosphere represent the optimal treatment conditions, among the process parameters, to obtain a single phase of Sm 2 SO 2 .
The work presented in this PhD thesis concerns the characterisation of the physical structure, co... more The work presented in this PhD thesis concerns the characterisation of the physical structure, composition and domain structure of advanced magnetic materials by electron microscopy within the FP6 European Research Training Network "Spinswitch". In particular the investigations concerned MgO/CoFeB/MgO multilayers to be employed in magnetic sensors (this work was done in collaboration with INESC-MN Lisbon-Portugal); Ni80Fe20/Cu electrodeposited nanowires to be employed as spin transfer torque devices (this work was done in collaboration with NIRDTP Iasi-Romania and University of Salamanca); multilayers with perpendicular anisotropy which represent potential candidates to be employed in the next generation of MRAMs (this work was done in collaboration with Spintec-CEA-Grenoble). Chapter 1 will provide an overview of the physics behind the topics treated during this work and a description of the general motivations of the research carried out. Chapter 2 will provide an overvi...
The work presented in this PhD thesis concerns the characterisation of the physical structure, co... more The work presented in this PhD thesis concerns the characterisation of the physical structure, composition and domain structure of advanced magnetic materials by electron microscopy within the FP6 European Research Training Network "Spinswitch". In particular the investigations concerned MgO/CoFeB/MgO multilayers to be employed in magnetic sensors (this work was done in collaboration with INESC-MN Lisbon-Portugal); Ni80Fe20/Cu electrodeposited nanowires to be employed as spin transfer torque devices (this work was done in collaboration with NIRDTP Iasi-Romania and University of Salamanca); multilayers with perpendicular anisotropy which represent potential candidates to be employed in the next generation of MRAMs (this work was done in collaboration with Spintec-CEA-Grenoble). Chapter 1 will provide an overview of the physics behind the topics treated during this work and a description of the general motivations of the research carried out. Chapter 2 will provide an overvi...
Nanotechnology, 2009
In this work, the effects of the focus ion beam (FIB) milling process on the optical properties o... more In this work, the effects of the focus ion beam (FIB) milling process on the optical properties of semiconductor nanostructures were investigated. With this aim, a sensitive materials system based on InGaAs/GaAs quantum dots with well known and excellent optical properties was selected for the FIB treatment. The FIB technique was used to locally remove a metallic mask deposited on top of the quantum dot sample. The photoluminescence (PL) signal, collected from the circular openings, was used to infer the possible damage effects of the ion beam on the properties of the dots.
Aluminum nitride (AlN) thin films were deposited on SiO 2 /Si substrates by radiofrequency (RF) m... more Aluminum nitride (AlN) thin films were deposited on SiO 2 /Si substrates by radiofrequency (RF) magnetron sputtering using an aluminum target. The influence of the deposition parameterssuch as nitrogen concentration in the sputtering atmosphere, RF power, total working pressure and substrate bias voltageon the structure, morphology and composition of the thin films was discussed. The structure was studied using X-ray diffraction (XRD), the morphology was studied using scanning electron microscopy (SEM) and the composition was studied using energy dispersive spectroscopy (EDS). These investigations showed that all of the films grew preferentially along the c-axis regardless of the deposition conditions, without the application of external heating, whereas the grain size and morphology strongly depended on the process parameters. Additional energy, which was supplied to the growing films by increasing the power or decreasing the working pressure, improved the crystallinity, but compressive stress was induced in the samples, thus resulting in a surface morphology evolution.
Thin Solid Films, Feb 2, 2009
Despite the success of Cu (In, Ga) Se2 (CIGS) based PV technology now emerging in several industr... more Despite the success of Cu (In, Ga) Se2 (CIGS) based PV technology now emerging in several industrial initiatives, concerns about the cost of In and Ga are often expressed. It is believed that the cost of those elements will eventually limit the cost reduction of this technology. One candidate to replace CIGS is Cu2ZnSnSe4 (CZTSe). We report the preliminary results of CZTSe thin films grown on bare and Mo coated glass through selenization of DC magnetron sputtered Cu/Zn/Sn precursor layers in an atmosphere of ...
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Papers by Eleonora Bellini