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Carlegrim, Elin
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Carlegrim, E., Zhan, Y., Li, F., Liu, X. & Fahlman, M. (2010). Characterization of the Ni/V(TCNE)x interface for hybrid spintronics applications. Organic electronics, 11(6), 1020-1024
Öppna denna publikation i ny flik eller fönster >>Characterization of the Ni/V(TCNE)x interface for hybrid spintronics applications
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2010 (Engelska)Ingår i: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 11, nr 6, s. 1020-1024Artikel i tidskrift (Refereegranskat) 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.

Nyckelord
Organic-based molecular magnets; Spintronics; Interfaces; Photoelectron spectroscopy; Magnetic semiconductors
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:liu:diva-56259 (URN)10.1016/j.orgel.2010.03.001 (DOI)000277935200008 ()
Anmärkning

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/

Tillgänglig från: 2010-05-05 Skapad: 2010-05-05 Senast uppdaterad: 2017-12-12
Carlegrim, E. (2010). Development of Organic-Based Thin Film Magnets for Spintronics. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Öppna denna publikation i ny flik eller fönster >>Development of Organic-Based Thin Film Magnets for Spintronics
2010 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2010. s. 49
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1317
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:liu:diva-56262 (URN)978-91-7393-385-8 (ISBN)
Disputation
2010-05-25, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2010-05-05 Skapad: 2010-05-05 Senast uppdaterad: 2020-02-19Bibliografiskt granskad
Zhan, Y., Holmström, E., Lizarraga, R., Eriksson, O., Liu, X., Li, F., . . . Fahlman, M. (2010). Efficient Spin Injection Through Exchange Coupling at Organic Semiconductor/Ferromagnet Heterojunctions. Advanced Materials, 22(14), 1626-1630
Öppna denna publikation i ny flik eller fönster >>Efficient Spin Injection Through Exchange Coupling at Organic Semiconductor/Ferromagnet Heterojunctions
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2010 (Engelska)Ingår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 22, nr 14, s. 1626-1630Artikel i tidskrift (Refereegranskat) Published
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.

Ort, förlag, år, upplaga, sidor
Wiley-VCH Verlagsgesellschaft, 2010
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:liu:diva-56460 (URN)10.1002/adma.200903556 (DOI)000277205900012 ()
Tillgänglig från: 2010-05-17 Skapad: 2010-05-17 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
Carlegrim, E., Zhan, Y., de Jong, M. P. & Fahlman, M. (2010). Electronic structure of thin film cobalt tetracyanoethylene, Co(TCNE)x. Synthetic metals, 161(17-18), 1892-1897
Öppna denna publikation i ny flik eller fönster >>Electronic structure of thin film cobalt tetracyanoethylene, Co(TCNE)x
2010 (Engelska)Ingår i: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 161, nr 17-18, s. 1892-1897Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
Elsevier, 2010
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:liu:diva-56261 (URN)10.1016/j.synthmet.2011.06.031 (DOI)000295564000016 ()
Anmärkning

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

Tillgänglig från: 2010-05-05 Skapad: 2010-05-05 Senast uppdaterad: 2017-12-12
Kapilashrami, M., Xu, J., Rao, K. V., Belova, L., Carlegrim, E. & Fahlman, M. (2010). Experimental evidence for ferromagnetism at room temperature in MgO thin films. JOURNAL OF PHYSICS-CONDENSED MATTER, 22(34), 345004
Öppna denna publikation i ny flik eller fönster >>Experimental evidence for ferromagnetism at room temperature in MgO thin films
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2010 (Engelska)Ingår i: JOURNAL OF PHYSICS-CONDENSED MATTER, ISSN 0953-8984, Vol. 22, nr 34, s. 345004-Artikel i tidskrift (Refereegranskat) Published
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.

Ort, förlag, år, upplaga, sidor
Iop Publishing Ltd, 2010
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:liu:diva-58778 (URN)10.1088/0953-8984/22/34/345004 (DOI)000280847200006 ()
Tillgänglig från: 2010-08-27 Skapad: 2010-08-27 Senast uppdaterad: 2015-05-13
Bhatt, P., Carlegrim, E., Kanciurzewska, A., de Jong, M. P. & Fahlman, M. (2009). Electronic structure of thin film iron-tetracyanoethylene: Fe(TCNE)x. Applied Physics A: Materials Science & Processing, 95(1), 131-138
Öppna denna publikation i ny flik eller fönster >>Electronic structure of thin film iron-tetracyanoethylene: Fe(TCNE)x
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2009 (Engelska)Ingår i: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 95, nr 1, s. 131-138Artikel i tidskrift (Refereegranskat) Published
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.

Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:liu:diva-17167 (URN)10.1007/s00339-008-5032-y (DOI)
Tillgänglig från: 2009-03-07 Skapad: 2009-03-07 Senast uppdaterad: 2017-12-13
Bhatt, P., Kanciurzewska, A., Carlegrim, E., Kapilashrami, M., Belova, L., Rao, K. V. & Fahlman, M. (2009). Ferromagnetism above room temperature in nickel–tetracyanoethylene thin films. Journal of Materials Chemistry, 19(36), 6610-6615
Öppna denna publikation i ny flik eller fönster >>Ferromagnetism above room temperature in nickel–tetracyanoethylene thin films
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2009 (Engelska)Ingår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 19, nr 36, s. 6610-6615Artikel i tidskrift (Refereegranskat) Published
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.

Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:liu:diva-20594 (URN)10.1039/b900756c (DOI)
Tillgänglig från: 2009-09-15 Skapad: 2009-09-15 Senast uppdaterad: 2017-12-13
Zhan, Y., Liu, X., Carlegrim, E., Li, F., Bergenti, I., Graziosi, P., . . . Fahlman, M. (2009). The role of aluminum oxide buffer layer in organic spin-valves performance. APPLIED PHYSICS LETTERS, 94(5), 053301
Öppna denna publikation i ny flik eller fönster >>The role of aluminum oxide buffer layer in organic spin-valves performance
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2009 (Engelska)Ingår i: APPLIED PHYSICS LETTERS, ISSN 0003-6951, Vol. 94, nr 5, s. 053301-Artikel i tidskrift (Refereegranskat) Published
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)].

Nyckelord
alumina, buffer layers, charge injection, cobalt, electronic structure, ferromagnetic materials, magnetic circular dichroism, MIS structures, organic semiconductors, spin valves, X-ray photoelectron spectra
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:liu:diva-16980 (URN)10.1063/1.3078274 (DOI)
Anmärkning

Original Publication:Yiqiang Zhan, Xianjie Liu, Elin Carlegrim, Fenghong Li, I Bergenti, P Graziosi, V Dediu and Mats Fahlman, The role of aluminum oxide buffer layer in organic spin-valves performance, 2009, APPLIED PHYSICS LETTERS, (94), 5, 053301.http://dx.doi.org/10.1063/1.3078274Copyright: American Institute of Physicshttp://www.aip.org/

Tillgänglig från: 2009-03-06 Skapad: 2009-02-27 Senast uppdaterad: 2015-05-18Bibliografiskt granskad
Carlegrim, E., Kanciurzewska, A., Nordblad, P. & Fahlman, M. (2008). Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications. Applied Physics Letters, 92(16), 163308
Öppna denna publikation i ny flik eller fönster >>Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications
2008 (Engelska)Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, nr 16, s. 163308-Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
Institutionen för teknik och naturvetenskap, 2008
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:liu:diva-11869 (URN)10.1063/1.2916901 (DOI)
Anmärkning
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.jspTillgänglig från: 2008-05-21 Skapad: 2008-05-21 Senast uppdaterad: 2017-12-13
Carlegrim, E., Gao, B., Kanciurzewska, A., de Jong, M. P., Wu, Z., Luo, Y. & Fahlman, M. (2008). Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet. Physical Review B. Condensed Matter and Materials Physics, 77, 054420
Öppna denna publikation i ny flik eller fönster >>Near-edge x-ray absorption studies of Na-doped tetracyanoethylene films: A model system for the V(TCNE)x room-temperature molecular magnet
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2008 (Engelska)Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, s. 054420-Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
Institutionen för teknik och naturvetenskap, 2008
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:liu:diva-11753 (URN)10.1103/PhysRevB.77.054420 (DOI)
Anmärkning
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/Tillgänglig från: 2008-05-07 Skapad: 2008-05-07 Senast uppdaterad: 2017-12-13
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