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  • 1.
    Bhatt, Pramod
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Kanciurzewska, A
    Adam Mickiewicz University Poznan.
    de Jong, M. P.
    University of Twente.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Electronic structure of thin film iron-tetracyanoethylene: Fe(TCNE)x2009In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 95, no 1, p. 131-138Article in journal (Refereed)
    Abstract [en]

    Thin film iron-tetracyanoethylene Fe(TCNE) x , x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE) x is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results. The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE) x system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T C ) seen for Fe(TCNE) x -type magnets.

  • 2.
    Bhatt, Pramod
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Kapilashrami, Mukes
    Division of Engineering Material Physics, Royal Institute of Technology, Stockholm, Sweden.
    Belova, Liubov
    Division of Engineering Material Physics, Royal Institute of Technology, Stockholm, Sweden.
    Rao, K V
    Division of Engineering Material Physics, Royal Institute of Technology, Stockholm, Sweden.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Ferromagnetism above room temperature in nickel–tetracyanoethylene thin films2009In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 19, no 36, p. 6610-6615Article in journal (Refereed)
    Abstract [en]

    Room temperature ferromagnetic ordering is reported in Ni–tetracyanoethylene (TCNE) thin films fabricated on Au substrates using physical vapor deposition (PVD) under ultra high vacuum conditions. This technique enables the preparation of very clean films without having any kind of contamination from oxygen-containing species, solvents or precursor molecules. Film stoichiometry was obtained from X-ray photoelectron spectroscopy (XPS) measurements. XPS derived stoichiometry points to a 1 : 2 ratio between Ni and TCNE resulting in Ni(TCNE)x, x ≈ 2. No evidence of pure Ni metal in the in situ grown films was present in the XPS or the ultraviolet photoelectron spectroscopy (UPS) measurements within the detection limits of the techniques.

  • 3.
    Carlegrim, Elin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Development of Organic-Based Thin Film Magnets for Spintronics2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the growing field of spintronics, development of semiconducting magnets is a high priority. Organic-based molecular magnets are attractive candidates since their properties can be tailor-made by organic chemistry. Other advantages include low weight and low temperature processing. Vanadium tetracyanoethylene, V(TCNE)x, x~2, is particularly interesting since it is one of very few semiconducting magnets with magnetic ordering above room temperature.

    The aim of the research presented in this thesis was to prepare and characterize thin film organic-based magnets with focus on V(TCNE)x. Photoelectron and absorption spectroscopy studies were performed leading to a more complete picture of the electronic and chemical structure of the material. Depending on the preparation method of V(TCNE)x, the material contains varying amounts of disorder which among other things makes it very air sensitive. In this thesis, a new preparation method for organic-based magnets based on physical vapor deposition is presented and the first result shows that it generates less air sensitive V(TCNE)x than previous methods reported. A new spin valve design based on V(TCNE)x was proposed where the material delivers both spin-filtering and spin-transporting functionality, making use of its fully spin-polarized transport levels. In such devices, the interface of V(TCNE)x with ferromagnetic metals is of great importance and was hence studied. As vanadium ions always are very reactive towards oxygen, substituting vanadium by a less reactive ion would be desirable from both an interface engineering and device packaging perspective. Very few alternatives exist however that orders magnetically above room temperature. In order to find out what are the key design criteria for preparing thin film semiconducting room temperature magnets, we have begun to study systems which order magnetically much below room temperature and compared them with V(TCNE)x.

    List of papers
    1. Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet
    Open this publication in new window or tab >>Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet
    Show others...
    2008 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, p. 054420-Article in journal (Refereed) Published
    Abstract [en]

    V(TCNE)x, with TCNE=tetracyanoethylene and x~2, is an organic-based molecular magnet with potential to be used in spintronic devices. With the aim of shedding light on the unoccupied frontier electronic structure of V(TCNE)x we have studied pristine TCNE and sodium-intercalated TCNE by near edge x-ray absorption fine structure (NEXAFS) spectroscopy as well as with theoretical calculations. Sodium-intercalated TCNE was used as a model system of the more complex V(TCNE)x and both experimental and theoretical results of the model compound have been used to interpret the NEXAFS spectra of V(TCNE)x. By comparing the experimental and theoretical C K-edge of pristine TCNE, the contributions from the various carbon species (cyano and vinyl) could be disentangled. Upon fully sodium intercalation, TCNE is n doped with one electron per molecule and the features in the C and N K-edge spectra of pristine TCNE undergo strong modification caused by partially filling the TCNE lowest unoccupied molecular orbital (LUMO). When comparing the C and N K-edge NEXAFS spectra of fully sodium-doped TCNE with V(TCNE)x, the spectra are similar except for broadening of the features which originates from structural disorder of the V(TCNE)x films. The combined results from the model system and V(TCNE)x suggest that the lowest unoccupied molecular orbital with density on the nitrogen atoms in V(TCNE)x has no significant hybridization with vanadium and is similar to the so-called singly occupied molecular orbital of the TCNE anion. This suggests that the LUMO of V(TCNE)x is TCNE or vanadiumlike, in contrast to the frontier occupied electronic structure where the highest occupied molecular orbital is a hybridization between V(3d) and cyano carbons. The completely different nature of the unoccupied and occupied frontier electronic structure of the material will most likely affect both charge injection and transport properties of a spintronic device featuring V(TCNE)x.

    Place, publisher, year, edition, pages
    Institutionen för teknik och naturvetenskap, 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-11753 (URN)10.1103/PhysRevB.77.054420 (DOI)
    Note
    Original publication: E. Carlegrim, B. Gao, A. Kanciurzewska, M. P. de Jong, Z. Wu, Y. Luo and M. Fahlman, Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet, 2008, Physical Review B, (77), 054420. http://dx.doi.org/10.1103/PhysRevB.77.054420. Copyright: The America Physical Society, http://prb.aps.org/Available from: 2008-05-07 Created: 2008-05-07 Last updated: 2017-12-13
    2. The unoccupied electronic structure of the semi-conducting room temperature molecular magnet V(TCNE)2
    Open this publication in new window or tab >>The unoccupied electronic structure of the semi-conducting room temperature molecular magnet V(TCNE)2
    2008 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 452, no 1-3, p. 173-177Article in journal (Refereed) Published
    Abstract [en]

    The unoccupied electronic structure of the organic-based magnet V(TCNE)x (TCNE = tetracyanoethylene, x~2) has been studied with near edge x-ray absorption fine structure (NEXAFS) and with photoelectron spectroscopy (PES). By studying V(TCNE)x upon sodium-doping, the electron-accepting state, i.e. the lowest unoccupied molecular orbital (LUMO) of V(TCNE)x was shown mainly to be localized on (TCNE)--units in contrast to the hole-accepting state, i.e. the highest occupied molecular orbital (HOMO), which previously was assigned primarily to be V(3d)-derived. This study also showed that there are trap states for electron transport located below the (TCNE)2- level, likely leading to decreased electron mobility.

    Place, publisher, year, edition, pages
    Institutionen för teknik och naturvetenskap, 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-11143 (URN)10.1016/j.cplett.2007.12.049 (DOI)
    Note
    Original publication: Elin Carlegrim, Anna Kanciurzewska, Michel P. de Jong, Carl Tengstedt and Mats Fahlman, The unoccupied electronic structure of the semi-conducting room temperature molecular magnet V(TCNE)2, 2008, Chemical Physics Letters, (452), 1-3, 173-177. http://dx.doi.org/10.1016/j.cplett.2007.12.049. Copyright: Elsevier Ltd, http://www.elsevier.com/Available from: 2008-02-27 Created: 2008-02-27 Last updated: 2017-12-13
    3. Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications
    Open this publication in new window or tab >>Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications
    2008 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 16, p. 163308-Article in journal (Refereed) Published
    Abstract [en]

    Herein, we report on a preparation method of vanadium tetracyanoethylene, V(TCNE)x, an organic-based semiconducting room temperature thin film magnet. Previously, this compound has been reported to be extremely air sensitive but this preparation method leads to V(TCNE)x, which can retain its magnetic ordering at least several weeks in air. The electronic structure has been studied by photoelectron spectroscopy and the magnetic properties by superconducting quantum interference device. The properties mentioned above, in combination with complete spin polarization, makes this air-stable V(TCNE)x a very promising material for spintronic devices.

    Place, publisher, year, edition, pages
    Institutionen för teknik och naturvetenskap, 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-11869 (URN)10.1063/1.2916901 (DOI)
    Note
    Original publication: Elin Carlegrim, Anna Kanciurzewska, Per Nordblad and Mats Fahlman, Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications, 2008, Applied Physics Letters, (92), 163308. http://dx.doi.org/10.1063/1.2916901. Copyright: American Institute of Physics, http://apl.aip.org/apl/top.jspAvailable from: 2008-05-21 Created: 2008-05-21 Last updated: 2017-12-13
    4. Characterization of the Ni/V(TCNE)x interface for hybrid spintronics applications
    Open this publication in new window or tab >>Characterization of the Ni/V(TCNE)x interface for hybrid spintronics applications
    Show others...
    2010 (English)In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 11, no 6, p. 1020-1024Article in journal (Refereed) Published
    Abstract [en]

    Vanadium tetracyanoethylene, V(TCNE)x, is an organic-based magnet with properties suitable for spintronics applications, e.g. spin valves. In this paper we propose a new hybrid organic spin valve design where V(TCNE)x is used as a spin-transporting and spin-filtering layer sandwiched between two ferromagnetic (FM) metal contacts, i.e. FM/V(TCNE)x/FM. As the spin injection and detection of such a device occurs at the interfaces the quality of those are of crucial importance. Therefore, the Ni/V(TCNE)x interface has been investigated by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption spectroscopy (NEXAFS) as well as compared with XPS results from a model system, Ni/TCNE. Ni chemically interact with both the vinyl and cyano groups but there is no evidence for significant diffusion of Ni into the V(TCNE)x film. As the chemical interaction affects the spin injection and detection negatively by modifying the lowest unoccupied molecular orbital (LUMO) and destroying the magnetic ordering network at the surface, these results indicate that there is need for a buffer layer between V(TCNE)x and Ni, and in extension most likely between V(TCNE)x and any FM contact.

    Keywords
    Organic-based molecular magnets; Spintronics; Interfaces; Photoelectron spectroscopy; Magnetic semiconductors
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-56259 (URN)10.1016/j.orgel.2010.03.001 (DOI)000277935200008 ()
    Note

    Original Publication: Elin Carlegrim, Yiqiang Zhan, Fenghong Li, Xianjie Liu and Mats Fahlman, Characterization of the Ni/V(TCNE)x interface for hybrid spintronics applications, 2010, Organic electronics, (11), 6, 1020-1024. http://dx.doi.org/10.1016/j.orgel.2010.03.001 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/

    Available from: 2010-05-05 Created: 2010-05-05 Last updated: 2017-12-12
    5. Electronic structure of thin film cobalt tetracyanoethylene, Co(TCNE)x
    Open this publication in new window or tab >>Electronic structure of thin film cobalt tetracyanoethylene, Co(TCNE)x
    2010 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 161, no 17-18, p. 1892-1897Article in journal (Refereed) Published
    Abstract [en]

    V(TCNE)x, TCNE=tetracyanoethylene, x~2, is a semiconducting organicbased magnet and one of very few organic-based magnets with critical temperature above room temperature (RT). With the aim to understand the key design criteria for achieving RT organic-based magnets we have started to study the electronic and chemical structure of members of the M(TCNE)x family with significantly lower critical temperatures than V(TCNE)x. In this paper, Co(TCNE)x, x~2, (Tc~44 K, derived from its powder form) were prepared by a method based on physical vapor deposition, resulting in oxygen-free thin films. The results propose Co(TCNE)x to contain to local bonding disorder in contrast to V(TCNE)x thin films, which can be grown virtually defect free. In addition, the Co L-edge does not show any pronounced fine structure, suggesting the crystal field to be very weak. By using a variety of photoemission and X-ray absorption techniques the highest occupied molecular orbital (HOMO) of Co(TCNE)x was determined to mainly be TCNE-derived while the states originating from Co(3d) are localized at higher binding energies. This is in stark contrast to V(TCNE)x where V(3d) is mainly responsible for the HOMO. As the HOMO of Fe(TCNE)x (Tc~121 K, derived from its powder form) is TCNE-derived these results show that Co(TCNE)x is more similar to Fe(TCNE)x than to V(TCNE)x in terms of electronic structure.

    Place, publisher, year, edition, pages
    Elsevier, 2010
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-56261 (URN)10.1016/j.synthmet.2011.06.031 (DOI)000295564000016 ()
    Note

    Funding agencies|Swedish Research Council||Knut and Alice Wallenberg Foundation||

    Available from: 2010-05-05 Created: 2010-05-05 Last updated: 2017-12-12
  • 4.
    Carlegrim, Elin
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Preparation and characterization of an organic-based magnet2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the growing field of spintronics there is a strong need for development of flexible lightweight semi-conducting magnets. Molecular organic-based magnets are attractive candidates since it is possible to tune their properties by organic chemistry, making them so-called “designer magnets”. Vanadium tetracyanoethylene, V(TCNE)x, is particularly interesting since it is a semiconductor with Curie temperature above room temperature (TC~400 K). The main problem with these organic-based magnets is that they are extremely air sensitive. This thesis reports on the frontier electronic structure of the V(TCNE)x by characterization with photoelectron spectroscopy (PES) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy. It also presents a new and more flexible preparation method of this class of organic-based thin film magnets. The result shows improved air stability of the V(TCNE)x prepared with this method as compared to V(TCNE)x prepared by hitherto used methods.

    List of papers
    1. Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet
    Open this publication in new window or tab >>Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet
    Show others...
    2008 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, p. 054420-Article in journal (Refereed) Published
    Abstract [en]

    V(TCNE)x, with TCNE=tetracyanoethylene and x~2, is an organic-based molecular magnet with potential to be used in spintronic devices. With the aim of shedding light on the unoccupied frontier electronic structure of V(TCNE)x we have studied pristine TCNE and sodium-intercalated TCNE by near edge x-ray absorption fine structure (NEXAFS) spectroscopy as well as with theoretical calculations. Sodium-intercalated TCNE was used as a model system of the more complex V(TCNE)x and both experimental and theoretical results of the model compound have been used to interpret the NEXAFS spectra of V(TCNE)x. By comparing the experimental and theoretical C K-edge of pristine TCNE, the contributions from the various carbon species (cyano and vinyl) could be disentangled. Upon fully sodium intercalation, TCNE is n doped with one electron per molecule and the features in the C and N K-edge spectra of pristine TCNE undergo strong modification caused by partially filling the TCNE lowest unoccupied molecular orbital (LUMO). When comparing the C and N K-edge NEXAFS spectra of fully sodium-doped TCNE with V(TCNE)x, the spectra are similar except for broadening of the features which originates from structural disorder of the V(TCNE)x films. The combined results from the model system and V(TCNE)x suggest that the lowest unoccupied molecular orbital with density on the nitrogen atoms in V(TCNE)x has no significant hybridization with vanadium and is similar to the so-called singly occupied molecular orbital of the TCNE anion. This suggests that the LUMO of V(TCNE)x is TCNE or vanadiumlike, in contrast to the frontier occupied electronic structure where the highest occupied molecular orbital is a hybridization between V(3d) and cyano carbons. The completely different nature of the unoccupied and occupied frontier electronic structure of the material will most likely affect both charge injection and transport properties of a spintronic device featuring V(TCNE)x.

    Place, publisher, year, edition, pages
    Institutionen för teknik och naturvetenskap, 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-11753 (URN)10.1103/PhysRevB.77.054420 (DOI)
    Note
    Original publication: E. Carlegrim, B. Gao, A. Kanciurzewska, M. P. de Jong, Z. Wu, Y. Luo and M. Fahlman, Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet, 2008, Physical Review B, (77), 054420. http://dx.doi.org/10.1103/PhysRevB.77.054420. Copyright: The America Physical Society, http://prb.aps.org/Available from: 2008-05-07 Created: 2008-05-07 Last updated: 2017-12-13
    2. The unoccupied electronic structure of the semi-conducting room temperature molecular magnet V(TCNE)2
    Open this publication in new window or tab >>The unoccupied electronic structure of the semi-conducting room temperature molecular magnet V(TCNE)2
    2008 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 452, no 1-3, p. 173-177Article in journal (Refereed) Published
    Abstract [en]

    The unoccupied electronic structure of the organic-based magnet V(TCNE)x (TCNE = tetracyanoethylene, x~2) has been studied with near edge x-ray absorption fine structure (NEXAFS) and with photoelectron spectroscopy (PES). By studying V(TCNE)x upon sodium-doping, the electron-accepting state, i.e. the lowest unoccupied molecular orbital (LUMO) of V(TCNE)x was shown mainly to be localized on (TCNE)--units in contrast to the hole-accepting state, i.e. the highest occupied molecular orbital (HOMO), which previously was assigned primarily to be V(3d)-derived. This study also showed that there are trap states for electron transport located below the (TCNE)2- level, likely leading to decreased electron mobility.

    Place, publisher, year, edition, pages
    Institutionen för teknik och naturvetenskap, 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-11143 (URN)10.1016/j.cplett.2007.12.049 (DOI)
    Note
    Original publication: Elin Carlegrim, Anna Kanciurzewska, Michel P. de Jong, Carl Tengstedt and Mats Fahlman, The unoccupied electronic structure of the semi-conducting room temperature molecular magnet V(TCNE)2, 2008, Chemical Physics Letters, (452), 1-3, 173-177. http://dx.doi.org/10.1016/j.cplett.2007.12.049. Copyright: Elsevier Ltd, http://www.elsevier.com/Available from: 2008-02-27 Created: 2008-02-27 Last updated: 2017-12-13
    3. Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications
    Open this publication in new window or tab >>Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications
    2008 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 16, p. 163308-Article in journal (Refereed) Published
    Abstract [en]

    Herein, we report on a preparation method of vanadium tetracyanoethylene, V(TCNE)x, an organic-based semiconducting room temperature thin film magnet. Previously, this compound has been reported to be extremely air sensitive but this preparation method leads to V(TCNE)x, which can retain its magnetic ordering at least several weeks in air. The electronic structure has been studied by photoelectron spectroscopy and the magnetic properties by superconducting quantum interference device. The properties mentioned above, in combination with complete spin polarization, makes this air-stable V(TCNE)x a very promising material for spintronic devices.

    Place, publisher, year, edition, pages
    Institutionen för teknik och naturvetenskap, 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-11869 (URN)10.1063/1.2916901 (DOI)
    Note
    Original publication: Elin Carlegrim, Anna Kanciurzewska, Per Nordblad and Mats Fahlman, Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications, 2008, Applied Physics Letters, (92), 163308. http://dx.doi.org/10.1063/1.2916901. Copyright: American Institute of Physics, http://apl.aip.org/apl/top.jspAvailable from: 2008-05-21 Created: 2008-05-21 Last updated: 2017-12-13
  • 5.
    Carlegrim, Elin
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Gao, B.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    de Jong, Michel P
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Wu, Z.
    Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
    Luo, Y.
    Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, p. 054420-Article in journal (Refereed)
    Abstract [en]

    V(TCNE)x, with TCNE=tetracyanoethylene and x~2, is an organic-based molecular magnet with potential to be used in spintronic devices. With the aim of shedding light on the unoccupied frontier electronic structure of V(TCNE)x we have studied pristine TCNE and sodium-intercalated TCNE by near edge x-ray absorption fine structure (NEXAFS) spectroscopy as well as with theoretical calculations. Sodium-intercalated TCNE was used as a model system of the more complex V(TCNE)x and both experimental and theoretical results of the model compound have been used to interpret the NEXAFS spectra of V(TCNE)x. By comparing the experimental and theoretical C K-edge of pristine TCNE, the contributions from the various carbon species (cyano and vinyl) could be disentangled. Upon fully sodium intercalation, TCNE is n doped with one electron per molecule and the features in the C and N K-edge spectra of pristine TCNE undergo strong modification caused by partially filling the TCNE lowest unoccupied molecular orbital (LUMO). When comparing the C and N K-edge NEXAFS spectra of fully sodium-doped TCNE with V(TCNE)x, the spectra are similar except for broadening of the features which originates from structural disorder of the V(TCNE)x films. The combined results from the model system and V(TCNE)x suggest that the lowest unoccupied molecular orbital with density on the nitrogen atoms in V(TCNE)x has no significant hybridization with vanadium and is similar to the so-called singly occupied molecular orbital of the TCNE anion. This suggests that the LUMO of V(TCNE)x is TCNE or vanadiumlike, in contrast to the frontier occupied electronic structure where the highest occupied molecular orbital is a hybridization between V(3d) and cyano carbons. The completely different nature of the unoccupied and occupied frontier electronic structure of the material will most likely affect both charge injection and transport properties of a spintronic device featuring V(TCNE)x.

  • 6.
    Carlegrim, Elin
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    de Jong, Michel P
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    The unoccupied electronic structure of the semi-conducting room temperature molecular magnet V(TCNE)22008In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 452, no 1-3, p. 173-177Article in journal (Refereed)
    Abstract [en]

    The unoccupied electronic structure of the organic-based magnet V(TCNE)x (TCNE = tetracyanoethylene, x~2) has been studied with near edge x-ray absorption fine structure (NEXAFS) and with photoelectron spectroscopy (PES). By studying V(TCNE)x upon sodium-doping, the electron-accepting state, i.e. the lowest unoccupied molecular orbital (LUMO) of V(TCNE)x was shown mainly to be localized on (TCNE)--units in contrast to the hole-accepting state, i.e. the highest occupied molecular orbital (HOMO), which previously was assigned primarily to be V(3d)-derived. This study also showed that there are trap states for electron transport located below the (TCNE)2- level, likely leading to decreased electron mobility.

  • 7.
    Carlegrim, Elin
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nordblad, Per
    Department of Engineering Sciences, Uppsala University, S-751 21 Uppsala, Sweden.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 16, p. 163308-Article in journal (Refereed)
    Abstract [en]

    Herein, we report on a preparation method of vanadium tetracyanoethylene, V(TCNE)x, an organic-based semiconducting room temperature thin film magnet. Previously, this compound has been reported to be extremely air sensitive but this preparation method leads to V(TCNE)x, which can retain its magnetic ordering at least several weeks in air. The electronic structure has been studied by photoelectron spectroscopy and the magnetic properties by superconducting quantum interference device. The properties mentioned above, in combination with complete spin polarization, makes this air-stable V(TCNE)x a very promising material for spintronic devices.

  • 8.
    Carlegrim, Elin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Zhan, Yiqiang
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    de Jong, M. P.
    MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Electronic structure of thin film cobalt tetracyanoethylene, Co(TCNE)x2010In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 161, no 17-18, p. 1892-1897Article in journal (Refereed)
    Abstract [en]

    V(TCNE)x, TCNE=tetracyanoethylene, x~2, is a semiconducting organicbased magnet and one of very few organic-based magnets with critical temperature above room temperature (RT). With the aim to understand the key design criteria for achieving RT organic-based magnets we have started to study the electronic and chemical structure of members of the M(TCNE)x family with significantly lower critical temperatures than V(TCNE)x. In this paper, Co(TCNE)x, x~2, (Tc~44 K, derived from its powder form) were prepared by a method based on physical vapor deposition, resulting in oxygen-free thin films. The results propose Co(TCNE)x to contain to local bonding disorder in contrast to V(TCNE)x thin films, which can be grown virtually defect free. In addition, the Co L-edge does not show any pronounced fine structure, suggesting the crystal field to be very weak. By using a variety of photoemission and X-ray absorption techniques the highest occupied molecular orbital (HOMO) of Co(TCNE)x was determined to mainly be TCNE-derived while the states originating from Co(3d) are localized at higher binding energies. This is in stark contrast to V(TCNE)x where V(3d) is mainly responsible for the HOMO. As the HOMO of Fe(TCNE)x (Tc~121 K, derived from its powder form) is TCNE-derived these results show that Co(TCNE)x is more similar to Fe(TCNE)x than to V(TCNE)x in terms of electronic structure.

  • 9.
    Carlegrim, Elin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Zhan, Yiqiang
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Li, Fenghong
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Characterization of the Ni/V(TCNE)x interface for hybrid spintronics applications2010In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 11, no 6, p. 1020-1024Article in journal (Refereed)
    Abstract [en]

    Vanadium tetracyanoethylene, V(TCNE)x, is an organic-based magnet with properties suitable for spintronics applications, e.g. spin valves. In this paper we propose a new hybrid organic spin valve design where V(TCNE)x is used as a spin-transporting and spin-filtering layer sandwiched between two ferromagnetic (FM) metal contacts, i.e. FM/V(TCNE)x/FM. As the spin injection and detection of such a device occurs at the interfaces the quality of those are of crucial importance. Therefore, the Ni/V(TCNE)x interface has been investigated by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption spectroscopy (NEXAFS) as well as compared with XPS results from a model system, Ni/TCNE. Ni chemically interact with both the vinyl and cyano groups but there is no evidence for significant diffusion of Ni into the V(TCNE)x film. As the chemical interaction affects the spin injection and detection negatively by modifying the lowest unoccupied molecular orbital (LUMO) and destroying the magnetic ordering network at the surface, these results indicate that there is need for a buffer layer between V(TCNE)x and Ni, and in extension most likely between V(TCNE)x and any FM contact.

  • 10.
    de Jong, Michel P
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Tengstedt, Carl
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Kanciurzewska, Anna
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Carlegrim, Elin
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Chemical bonding in V (TCNE)x (x~2) thin-film magnets grown in situ2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 6Article in journal (Refereed)
    Abstract [en]

    The molecule-based magnet V (TCNE)x, with TCNE=tetracyanoethylene, x˜2, shows an exceptionally high magnetic ordering temperature of about 400 K. With the aim to shed light on the origins of the robust magnetic ordering interactions, we have characterized the chemical bonding in V (TCNE)x thin films, prepared by an in situ chemical vapor deposition method, using photoelectron spectroscopy, x-ray absorption spectroscopy (XAS), and x-ray magnetic circular dichroism (XMCD). The XAS and XMCD results were interpreted by ligand field multiplet and charge transfer multiplet calculations, which show that the V-NC bonds are characterized by a large crystal field parameter 10Dq=2.3 eV and strong ligand to metal charge transfer effects, resulting in a hybrid V (3d) -CN ground state given by 60% 3 d3 and 40% 3 d4 L, where L is a hole on the cyano ligands. © 2007 The American Physical Society.

  • 11.
    Jönsson, Stina
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Salaneck, William R
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Photoelectron spectroscopy of the contact between the cathode and the active layers in plastic solar cells: the role of LiF2005In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 44, no 6A, p. 3695-3701Article in journal (Refereed)
    Abstract [en]

    The surfaces and electrode interfaces of a polymer blend used in prototype solar cells have been characterized with photoelectron spectroscopy. The polymer blend in question is a 1:4 mixture of APFO-3:PCBM. Based on surface analysis of the pristine film we can conclude that the surface of the blend is a 1:1 mixture of APFO-3 and PCBM. The electrode systems studied are the widely used Al and Al/LiF contacts. LiF prevents formation at the Al/organic interface of Al-organic complexes that destroy the π-conjugation. In addition to this, there are two other beneficial, thickness dependent, effects. Decomposition of LiF occurs for thin enough layers in which the LiF species are in contact with both the organic film and the Al atoms, which creates a low workfunction contact. For thicker (multi)layers, the dipole formed at the LiF/organic interface is retained as no decomposition of the LiF occurs upon Al deposition.

  • 12.
    Kanciurzewska, Anna
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Dobruchowska, E.
    Baranzahi, Amir
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Carlegrim, Elin
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Girtu, M. A.
    Study on Poly(3,4-ethylene dioxythiophene)-Poly(styrenesulfonate) as a plastic counter electrode in dye sensitized solar cells2007In: Journal of Optoelectronics and Advanced Materials, ISSN 1454-4164, E-ISSN 1841-7132, Vol. 9, no 4, p. 1052-1059Article in journal (Refereed)
    Abstract [en]

    Dye sensitized solar cells with PEDOT-PSS coated directly on flexible polyester substrate as counter electrode have been fabricated. The behavior of such plastic counter electrode in the presence of I/I-3 redox electrolyte has been investigated with X-ray photoelectron spectroscopy. We have found that some of iodine species are "trapped" within the PEDOT-PSS layer. The presence of I-3, I-2 and PEDOT charge transfer complexes with iodine species may block the surface of the electrode. Furthermore, the PEDOT may be further oxidized (p-doped) during cell operation, which in turn may cause overoxidation and loss of conductivity in the PEDOT-PSS film. Additionally, the interactions between PEDOT and iodine species may be enlarged because of the partial loss of PSS protective counter ion. That has resulted in decrease of PEDOT-PSS catalytic activity for reduction of I-3 to I in the redox electrolyte and has caused worse cell performance than in case of DSSC with Pt counter electrode.

  • 13.
    Kanciurzewska, Anna
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Dobruchowska, Ewa
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Baranzahi, Amir
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Ana
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Girtu, Mihai A.
    Dye sensitized solar cells with a plastic counter electrode of poly(3,4-ethylene dioxythiophene)-poly(styrenesulfonate) - art. no. 6656112007In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 6656, p. 65611-65611Article in journal (Refereed)
    Abstract [en]

    n/a

  • 14.
    Kapilashrami, Mukes
    et al.
    Royal Institute of Technology.
    Xu, Jun
    Royal Institute of Technology.
    Rao, K V
    Royal Institute of Technology.
    Belova, Lyuba
    Royal Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Experimental evidence for ferromagnetism at room temperature in MgO thin films2010In: JOURNAL OF PHYSICS-CONDENSED MATTER, ISSN 0953-8984, Vol. 22, no 34, p. 345004-Article in journal (Refereed)
    Abstract [en]

    Ferromagnetic ordering at room temperature (RTFM) in MgO thin films deposited by RF magnetron sputtering under various atmospheric conditions and temperatures is reported. A saturation magnetization (MS) value as high as 1.58 emu g(-1) is (0.046 mu B/unit cell) observed for a 170 nm film deposited at RT under an oxygen pressure of 1.3 x 10(-4) mbar. In contrast, films deposited at elevated temperature (under an identical oxygen pressure), or at higher oxygen pressures, as well as under a nitrogen atmosphere at RT show significantly suppressed magnetization. The ferromagnetic order in the MgO matrix is believed to be defect induced.

  • 15.
    Tengstedt, Carl
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    de Jong, M. P.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    V(TCNE)x: the electronic structure of an enigmatic, organic-based room temperature magnet revealedManuscript (preprint) (Other academic)
    Abstract [en]

    We have prepared and characterized thin films of V(TCNE)x in ultra-high vacuum using a novel film growth technique based on in-situ chemical vapor deposition of tetracyanoethylene, TCNE, and bis-benzene vanadium, V(C6H6)2. The in-situ preparation method enabled, for the first time, experimental analysis of the electronic structure. X-ray magnetic circular dichroism (XMCD) measurements recorded at the V L2,3-edge confirmed room temperature magnetic ordering. A combination of conventional photoelectron spectroscopy (PES) and resonant photoemission (RPE) measured at the x-ray absorption edges (V L3-edge, C K-edge, N K-edge) shows that the highest occupied electronic state is V(3d)-derived. Nearly complete quenching of the V(3d) orbital angular momentum is observed from the low value of the integrated XMCD signal, indicating a strong ligand field. The rearrangements of the TCNE" related valance electronic states observed in PED and near edge x-ray absorption fine structure (NEXAFS) spectra, in combination with the evidence of V(3d) and TCNE" π (π*) orbital overlap contained in RPE spectra, also point to strong, covalent type bonding.

  • 16.
    Tengstedt, Carl
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    de Jong, Michel P
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Kanciurzewska, Anna
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Carlegrim, Elin
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    X-ray magnetic circular dichroism and resonant photomission of V(TCNE)x hybrid magnets2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 96, no 5Article in journal (Refereed)
    Abstract [en]

    Thin films of V(TCNE)x were deposited in ultrahigh vacuum using a film growth technique based on in situ chemical vapor deposition of tetracyanoethylene, TCNE, and bis-benzene vanadium, V(C6H6)2. The in situ preparation method enabled, for the first time, experimental analysis of oxygen-free films. X-ray magnetic circular dichroism measurements recorded at the V L2,3 edge confirmed room temperature magnetic ordering. A combination of conventional photoelectron spectroscopy (PES) and resonant photoemission (RPE) measured at the V L3 edge shows that the highest occupied electronic state is V(3d) derived. The rearrangements of the TCNE- related valence electronic states observed in PES and the evidence of V(3d) and TCNE- p(p*) orbital overlap contained in RPE spectra, indicate that strong, covalent type bonding occurs between the vanadium and the TCNE molecules. © 2006 The American Physical Society.

  • 17.
    Zhan, Yiqiang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Holmström, Erik
    Instituto de Física, Universidad Austral de Chile, Valdivia (Chile) and Theoretical Division, Los Alamos National Laboratory Los Alamos, NM (USA).
    Lizarraga, Raquel
    Instituto de Física, Universidad Austral de Chile, Valdivia (Chile) and Theoretical Division, Los Alamos National Laboratory Los Alamos, NM (USA).
    Eriksson, Olle
    Department of Physics and Materials Science Uppsala University, Uppsala (Sweden).
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Li, Fenghong
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Efficient Spin Injection Through Exchange Coupling at Organic Semiconductor/Ferromagnet Heterojunctions2010In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 22, no 14, p. 1626-1630Article in journal (Refereed)
    Abstract [en]

    The schematic visualization of the Alq(3) molecule on the Fe substrate with the optimized geometry at lowest total energy. When the Alq(3) molecule is relaxed on the surface, only two of the wings are lying down on the Fe surface, and the third wing remains perpendicular to the surface, showing a strong hybridization occurance.

  • 18.
    Zhan, Yiqiang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Li, Fenghong
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Bergenti, I
    CNR, Italy.
    Graziosi, P
    CNR, Italy.
    Dediu, V
    CNR, Italy.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    The role of aluminum oxide buffer layer in organic spin-valves performance2009In: APPLIED PHYSICS LETTERS, ISSN 0003-6951, Vol. 94, no 5, p. 053301-Article in journal (Refereed)
    Abstract [en]

    The electronic structures of the 8-hydroxyquinoline-aluminum (Alq(3))/Al2O3/Co interfaces were studied by photoelectron spectroscopy. A strong interface dipole was observed, which leads to a reduction in the electron injection barrier. The x-ray photoelectron spectroscopy spectra further indicate that the Al2O3 buffer layer prevents the chemical interaction between Alq(3) molecules and Co atoms. X-ray magnetic circular dichroism results demonstrate that a Co layer deposited on an Al2O3 buffered Alq(3) layer shows better magnetic ordering in the interface region than directly deposited Co, which suggests a better performance of spin valves with such a buffer layer. This is consistent with the recent results from [Dediu , Phys. Rev. B 78, 115203 (2008)].

1 - 18 of 18
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