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web report not yet submitted
Home Institution: University of Zurich
Host Institution: CNR SPIN (University of Salerno)
STSM period: 29 Jan – 9 Feb 2018
We worked on the theory development in order to explain recent data measured with angleresolved photoemission spectroscopy of alkali surface-doping the Mott insulator Ca2Ru04. In the first week we discussed thoroughly the data in a systematic way and pinned down the key features in the experimental outcomes. (1) Starting from the clean Mott insulator, initial alkali metal deposition increased the measured spectral Mott gap. (2) With increasing deposition, significant spectral weight transfer has been observed towards the Fermi level. (3) After a criticai deposition the Mott gap closes and (4) a quantum well like state appears at the Fermi level.
In the second week, we developed a model in which the alkali impurity-induced bands hybridize with the ruthenium bands. Detailed calculations of this impurity model are now being carried out.
Impact: Past collaborative effort that resulted in high profile publications, the fruitful scientific stay in the framework of this STSM and the closeness of our fields of interest will naturally result in future collaborations. We already have severa! projects on other ruthenate compounds in progress that are very promising, judged from preliminary ARPES data.
Home Institution: University of Southeastern Norway
Host Institution: Technical University of Denmark
STSM period: 25/11/2017 to 06/01/2018
Based on photocatalysts, hydrogen generation via solar-energy driven water splitting provides the potential to reduce and eliminate the dependence on fossil fuels. As one of the most important photocatalysts, TiO2 has been studied deeply and considered promising candidates since the first trial of using TiO2 to extract hydrogen from water 1972 by Fujishima and Honda. However, the major disadvantage of wide band gap in TiO2, which resulted in mainly absorption and conversion of only UV light energy, have not yet been completely resolved.
Through simple thermal annealing process at temperature of 500 centigrade degree, the surficial TiO2 thin film on the Ti substrate is supposed to be highly relative to mixed-phases TiO2 due to the phase transformation caused by the thermal treatment. In order to verify the phase transition, advanced oxide film characterization is planned to conduct in the Host institution with the help of special instruments, such as X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS).
Impact: One Journal paper (Under Review).
Home Institution: IREC – Catalonia Institute for Energy Research
Host Institution: University of Cambridge
STSM period: 10/01/2018 to 10/03/2018
The stay has been devoted to the development of novel cathode materials for solid oxide cells in the form of composite thin films. In particular, focus has been put on the fabrication and characterization of vertically aligned nanostructured in which an electronic conductor (La0.8Sr0.2MnO3) is immersed in a fluorite matrix possessing high ionic conductivity (doped ceria or stabilized zirconia). Dedicated investigations have been carried on the influence of the fabrication conditions (pulsed laser deposition) on the final microstructure by using complementary experimental methods (diffraction and microscopy). A number of samples has been selected and the electrochemical properties are now investigated in order to study the potential of the so-obtained composite for cathode application (oxygen reduction kinetics).
Impact: Oral presentation by M. Acosta at “Interfaces in Energy Materials” conference, Cambridge 10-12 April 2018. Title: “Epitaxial Mesoporous Thin Films for Solid Oxide Fuel Cells Cathodes”.
Home Institution: CentraleSupelec
Host Institution: Magnetic Materials and Functional Oxides, Institut de Ciencia de Materials de Barcelona (ICMAB – CSIC)
STSM period: 09.01 – 09.03.2018
Solid solutions Ba(Sn,Ti)O3 were studied for the first time from the point of view of optical properties and photoconduction. In Ba(Sn,Ti)O3 ferroelectricity is combined with presence of Sn 5s 5p states in conduction band, enhancing charge separation and electron mobility, and thus improving photovoltaic efficiency. In this project, we studied the photo-response in Ba(Sn,Ti)O3 ceramics under lasers of different energy. First, we explored different electrode configurations and chose the in-plane configuration to analyse the conduction in the thin surface layer where the light absorption happens, thus the signal is maximized. Analysis of different ceramic compositions shows that Ba(Sn0.1Ti0.9)O3 is the most tin-rich one which produces the intrinsic ferroelectric photocurrent. Based on that, we chose this composition to explore the strain effects on photocurrent efficiency through thin film growth in further work. This project helped me personally to learn the know-how of experimental photocurrent measurement and in general strengthened the collaboration between our laboratories.
Impact: The work on publishing the results is in progress. Some of them will be included in the oral contribution to CIMTEC 2018 International Ceramics Congress, in Perugia, Italy on June 4-8, and the STSM COST action will be acknowledged.
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Home Institution: Institut de Ciència de Materials de
Host Institution: Technische Universität Darmstadt,
Department of Materials Science
STSM period: 28/01/2018 – 10/03/2018
During the STSM activity I studied the pulsed laser deposition of strontium niobate – SrNbO3 – thin films. This
material is believed to be a very good Transparent Conducting Oxides (TCO), combining high electrical
conductivity and high transparency to visible light. TCOs are more and more valued by materials scientists since
it is a crucial component when used as electrode in all-oxide devices (solar cell, TFT, varactor, etc.). However,
the literature about this material is very poor. In this context, both Mulfox (home) and ATFT (host) groups
develop TCOs and had interest in studying SrNbO3.
Main part of the activity has been done on optimizing the growth of SrNbO3 on different substrates changing a large set of parameters. All this work needed characterization techniques provided by both institutions. Finally, we could deposit films with a conductivity similar to literature reported values, and to other famous TCOs (e.g. SrVO3 and SrMoO3). Optical characterization is still in progress.
In conclusion, fast progress has been done on the development of SrNbO3 thin films. From a personal point of
view, I have also learned a lot from this project. Therefore, I would like to thank the Cost TO-BE Action, my
supervisor Prof. Fontcuberta, as well as Prof. Alff (leader of the ATFT group) for making this collaboration
Impact: As there is still a lot to be done concerning the growth of this material, further collaboration and a new stay at the host institution would be desirable. The final aim would be to complete a joint manuscript of this work.