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Dannetun, Per
Publications (10 of 14) Show all publications
Dannetun, P., Schott, M. & Vilar, M. (1996). High-resolution electron energy loss spectroscopy of thin crystalline highly oriented films of poly(tetrafluoroethylene). Thin Solid Films, 286(1-2), 321-329
Open this publication in new window or tab >>High-resolution electron energy loss spectroscopy of thin crystalline highly oriented films of poly(tetrafluoroethylene)
1996 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 286, no 1-2, p. 321-329Article in journal (Refereed) Published
Abstract [en]

High-resolution electron energy loss spectroscopy (HREELS) spectra of highly oriented films of poly(tetrafluoroethylene) (PTFE) are reported. With one exception, all peaks in the spectra correspond to IR active vibrations. They are well resolved, and with a remarkably high intensity, more than two orders of magnitude greater than we have observed on any other polymer in HREELS. The angular distributions of the elastic peak, and of the vibrational peaks are very narrow, which indicates both a well ordered system and a dipolar scattering behaviour. No evidence of amorphous regions in these films is found. A Raman active mode can be observed in off-specular geometry, using an incident electron beam coplanar with the PTFE fibers direction. This corresponds to resonance excitation of a transient negative ion state, with a maximum cross-section at an incident electron kinetic energy of about 4 eV.

Place, publisher, year, edition, pages
Elsevier, 1996
Keywords
Electron energy loss spectroscopy (EELS), Infrared spectroscopy, Polymers
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-124180 (URN)10.1016/S0040-6090(95)08530-0 (DOI)
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
Lögdlund, M., Dannetun, P., Fredriksson, C., Salaneck, W. R. & Brédas, J. L. (1996). Theoretical and experimental studies of the interaction between sodium and oligothiophenes. Physical Review B. Condensed Matter and Materials Physics, 53(24), 16327-16333
Open this publication in new window or tab >>Theoretical and experimental studies of the interaction between sodium and oligothiophenes
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1996 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 53, no 24, p. 16327-16333Article in journal (Refereed) Published
Abstract [en]

Quantum-chemical calculations and ultraviolet photoelectron spectroscopy (UPS) measurements have been performed in order to study the interaction between sodium and oligothiophenes, with a focus on the origin of experimentally observed relaxation energy effects in alkali-metal-doped conjugated molecules. Upon doping of a -sexithienylene (α-6T) with sodium atoms, (1) a broad feature appears in the valence band, in an energy region corresponding to the band gap in pristine α-6T, and (2) certain structural features in the valence band shift towards lower binding energies in the doped material. In particular, upon doping, a structural peak related to electronic levels mainly localized to the sulfur and b-carbon atoms destabilizes to an energy corresponding to that of the valence-band edge in pristine α-6T. The results of ab initio Hartree-Fock and local-spin-density calculations on α-trithienylene and bithiophene are consistent with the experimental data, and allow for an assignment of these destabilization effects in terms of initial-state relaxations. We stress that similar destabi-lization effects, reported for other alkali-metal-doped conjugated systems, had previously been proposed to be associated with final-state electronic screening, i.e., a dynamic artifact within the UPS measurements; this is in contradiction to the results of our ab initio theoretical studies. Our present results show that all structural features in the UPS data are contained in the results of sufficiently complete quantum chemical calculations.

Place, publisher, year, edition, pages
American Physical Society, 1996
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-124179 (URN)10.1103/PhysRevB.53.16327 (DOI)A1996WR76200035 ()
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
Lazzaroni, R., Lögdlund, M., Calderone, A., Brédas, J. L., Dannetun, P., Fauquet, C., . . . Salaneck, W. R. (1995). Chemical and electronic aspects of metal/conjugated polymer interfaces: Implications for electronic devices. Paper presented at Proceedings of the International Conference on Science and Technology of Synthetic Metals (ICSM ’94), Seoul, Korea, 24–29 July 1994, Vols. 69/71. Synthetic metals, 71(1-3), 2159-2162
Open this publication in new window or tab >>Chemical and electronic aspects of metal/conjugated polymer interfaces: Implications for electronic devices
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1995 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 71, no 1-3, p. 2159-2162Article in journal (Refereed) Published
Abstract [en]

The chemical nature and the electronic structure of metal/conjugated polymer interfaces are investigated in the context of polymer-based light-emitting diodes. We consider the interaction of low-workfunction metals (Al, Ca) with the surface of conjugated polymers or model oligomer molecules with a combined experimental and theoretical approach. The early stages of the interface formation are followed with X-ray and ultraviolet photoelectron spectroscopies and the experimental data are compared to the results of quantum chemical calculations. The reactions of Al and Ca with the organic surface are found to be fundamentally different: while the former forms new covalent bonds onto the polymer backbone, the latter tends to dope the conjugated system. Both types of reaction are expected to modify drastically the electronic properties of the polymer semiconductor.

Place, publisher, year, edition, pages
Elsevier, 1995
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-124177 (URN)10.1016/0379-6779(94)03203-I (DOI)A1995QT32600261 ()
Conference
Proceedings of the International Conference on Science and Technology of Synthetic Metals (ICSM ’94), Seoul, Korea, 24–29 July 1994, Vols. 69/71
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
Fauquet, C., Dannetun, P., Fredriksson, C., Stafström, S., Bourée, J. E., Brillaud, P., . . . Salaneck, W. R. (1995). Electronic structure of trimethylamine alane in the solid state. Chemical Physics Letters, 235(5-6), 528-534
Open this publication in new window or tab >>Electronic structure of trimethylamine alane in the solid state
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1995 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 235, no 5-6, p. 528-534Article in journal (Refereed) Published
Abstract [en]

The chemical and electronic structure of ultrathin molecular films of trimethylamine alane (TMAA), condensed in UHV at − 100°C, have been studied in the solid state, using both X-ray and ultraviolet photoelectron spectroscopy. The results are analyzed with the help of quantum chemical calculations at the ab initio Hartree-Fock 6-31G∗ level. Based upon the good agreement between theory and experimental, it is determined that clean, oxygen-free, condensed molecular solid films consist of the 2:1 adduct of TMAA, which was previously uncertain. In addition, based upon the electronic structure results, it is clear that the mechanism of the photodecomposition of TMAA can be explained in terms of the wavefunction of electrons photoexcited into the first unoccupied molecular orbital.

Place, publisher, year, edition, pages
Elsevier, 1995
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-124178 (URN)10.1016/0009-2614(95)00133-O (DOI)A1995QP34400022 ()
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
Dannetun, P., Fahlman, M., Fauquet, C., Kaerijama, K., Sonoda, Y., Lazzaroni, R., . . . Salaneck, W. R. (1994). Interface formation between poly(2,5-diheptyl-p-phenylenevinylene) and calcium: implications for light-emitting diodes. Paper presented at Symposium D on Organic Materials for Electronics - Polymer Interfaces with Metals and Semiconductors, at the 1994 E-MRS Spring Conference, Strasbourg, France, May 24-27, 1994. Synthetic metals, 67(1-3), 133-136
Open this publication in new window or tab >>Interface formation between poly(2,5-diheptyl-p-phenylenevinylene) and calcium: implications for light-emitting diodes
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1994 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 67, no 1-3, p. 133-136Article in journal (Refereed) Published
Abstract [en]

The early stages of metal/polymer interface formation between calcium and poly(2,5-diheptyl-p-phenylenevinylene) (PDHPV) have been studied using both X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Charge transfer is observed from the metal atoms to the polymer; as a result the calcium atoms at the interface are ionic, and negative bipolarons appear as the charge-carrying species on the polymer chains. This n-type doping of PDHPV by calcium leads to the appearance of new electronic states in the polymer bandgap. The calcium atoms appear to diffuse into the near surface region of the polymer, rather than forming a well-defined overlayer on the organic films.

Place, publisher, year, edition, pages
Elsevier, 1994
Keywords
Interface, Diodes, Poly(2, 5-diheptyl-p-phenylenevinylene), Calcium
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-124174 (URN)10.1016/0379-6779(94)90026-4 (DOI)A1994PW12000024 ()
Conference
Symposium D on Organic Materials for Electronics - Polymer Interfaces with Metals and Semiconductors, at the 1994 E-MRS Spring Conference, Strasbourg, France, May 24-27, 1994
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
Bröms, P., Fahlman, M., Xing, K. Z., Salaneck, W. R., Dannetun, P., Cornil, J., . . . Friend, R. H. (1994). Optical absorption studies of sodium doped poly(cyanoterephthalylidene). Paper presented at Symposium D on Organic Materials for Electronics - Polymer Interfaces with Metals and Semiconductors, at the 1994 E-MRS Spring Conference, Strasbourg, France, May 24-27, 1994. Synthetic metals, 67(1-3), 93-96
Open this publication in new window or tab >>Optical absorption studies of sodium doped poly(cyanoterephthalylidene)
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1994 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 67, no 1-3, p. 93-96Article in journal (Refereed) Published
Abstract [en]

The effects of doping poly(cyanoterephthalylidene) with sodium in ultrahighvacuum been studied by optical absorption spectroscopy. Upon doping, new optical transitions are observed within the bandgap; the characteristics of these transitions are consistent with the formation of bipolarons. The optical absorption results are confirmed by direct measurements of the doping-induced gap states using ultraviolet photoelectron spectroscopy.

Place, publisher, year, edition, pages
Elsevier, 1994
Keywords
Optical absorption, Doping, Poly(cyanoterephthalylidene)
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-124175 (URN)10.1016/0379-6779(94)90017-5 (DOI)A1994PW12000015 ()
Conference
Symposium D on Organic Materials for Electronics - Polymer Interfaces with Metals and Semiconductors, at the 1994 E-MRS Spring Conference, Strasbourg, France, May 24-27, 1994
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
Dannetun, P., Lögdlund, M., Fredriksson, C., Lazzaroni, R., Fauquet, C., Stafström, S., . . . Salaneck, W. R. (1994). Reactions of low work function metals Na, Al, and Ca on α,ω-€diphenyltetradecaheptaene. Implications for metal/polymer interfaces. Journal of Chemical Physics, 100(9), 6765-6771
Open this publication in new window or tab >>Reactions of low work function metals Na, Al, and Ca on α,ω-€diphenyltetradecaheptaene. Implications for metal/polymer interfaces
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1994 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 100, no 9, p. 6765-6771Article in journal (Refereed) Published
Abstract [en]

The interactions between different low work function metals aluminium,calcium and sodium, and α,ω‐diphenyltetradecaheptaene, a model molecule for certain conjugated polymers, have been investigated using both x‐ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The spectra are interpreted with the help of the results of quantum chemical calculations performed within the local spin density (LSD) approximation methodology. The metals are found to interact with the conjugated system in very different ways. Aluminium forms a covalent bond, which strongly modifies the π‐electronic structure of the conjugated molecule, while both the sodium and the calcium atoms act as doping agents, inducing new states in the otherwise forbidden bandgap. These new gap states can be viewed as a soliton–antisoliton pair for the Na/DP7 and a bipolaronic‐like defect for Ca/DP7.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 1994
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-124172 (URN)10.1063/1.467035 (DOI)A1994NH84600072 ()
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
Barta, P., Dannetun, P., Stafström, S., Zagórska, M. & Pron, A. (1994). Temperature evolution of the electronic band structure of the undoped and doped regioregular analog of poly(3‐alkylthiophenes): A spectroscopic and theoretical study. Journal of Chemical Physics, 100(2), 1731-1741
Open this publication in new window or tab >>Temperature evolution of the electronic band structure of the undoped and doped regioregular analog of poly(3‐alkylthiophenes): A spectroscopic and theoretical study
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1994 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 100, no 2, p. 1731-1741Article in journal (Refereed) Published
Abstract [en]

The undoped and ferric chloride p‐doped ‘‘head‐to‐head’’ ‘‘tail‐to‐tail’’ analog of poly(3‐decylthiophene) obtained from substituted bithiophenes, i.e., poly(4,4’didecyl‐2,2’bithiophene)‐PDDBT has been investigated. The samples were studied by means of ultraviolet photoelectron spectroscopy,optical absorption measurements, and polymerbands structure calculations. Experiments were carried out at different temperatures between 100 °C and −180 °C. The results indicate that PDDBT is nonplanar in the undoped state. No temperature effects have been observed in the π‐electron properties. In the doped state, however, lowering of the temperature results in an increase of the system planarity that modifies the electronic band structure. This effect has been shown to be fully reversible with temperature.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 1994
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-124171 (URN)10.1063/1.466600 (DOI)A1994MT00700105 ()
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
Lazzaroni, R., Brédas, J. L., Dannetun, P., Fredriksson, C., Stafström, S. & Salaneck, W. R. (1994). The chemical and electronic structure of the interface between aluminum and conjugated polymers. Electrochimica Acta, 39(2), 235-244
Open this publication in new window or tab >>The chemical and electronic structure of the interface between aluminum and conjugated polymers
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1994 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 39, no 2, p. 235-244Article in journal (Refereed) Published
Abstract [en]

The chemical and electronic structure of the interface between aluminum and several proto-typical conjugated systems is investigated with a combined experimental and theoretical approach. The experiments consists of following the evolution of the polymer surface during the early stages of aluminum deposition, with X-ray and Ultraviolet Photoelectron Spectroscopies (XPS, UPS). In parallel, quantum chemical calculations are performed on model oligomer systems interacting with isolated Al atoms. Aluminum is found to interact strongly with the polymer chain. New covalent Al-carbon bonds are formed along the polymer backbone; the chain geometry is deeply modified and the π electron conjugation can be dramatically reduced.

Place, publisher, year, edition, pages
Elsevier, 1994
Keywords
polymer-based devices, interface chemistry, electronic structure
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-124170 (URN)10.1016/0013-4686(94)80059-6 (DOI)A1994MP69200009 ()
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
Dannetun, P., Lögdlund, M., Fahlman, M., Fauquet, C., Beljonne, D., Brédas, J. L., . . . Salaneck, W. R. (1994). The evolution of charge-induced gap states in degenerate and non-degenerate conjugated molecules and polymers as studied by photoelectron spectroscopy. Paper presented at Symposium D on Organic Materials for Electronics - Polymer Interfaces with Metals and Semiconductors, at the 1994 E-MRS Spring Conference, Strasbourg, France, May 24-27, 1994. Synthetic metals, 67(1), 81-86
Open this publication in new window or tab >>The evolution of charge-induced gap states in degenerate and non-degenerate conjugated molecules and polymers as studied by photoelectron spectroscopy
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1994 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 67, no 1, p. 81-86Article in journal (Refereed) Published
Abstract [en]

We report the results of ultraviolet photoelectron spectroscopy (UPS) studies of the interaction between sodium and conjugated systems for a series of diphenylpolyees and diffrent oligomers of poly(p-phenylenevinylene) (PPV). The diphenylpolyenes include molecules containing two (i.e., stilbene) to 14 carbon atoms in the polyene part; stilbene itself can also be considered as a phenyl-capped monomer of PPV. Furthermore, a PPV oligomer with three phenylene units, as well as PPV itself, has been studied. The experimental results are interpreted with the help of quantum-chemical calculations using the Hartree-Fock semi-empirical Austin Model 1 (AM1) and valence-effective Hamiltonian (VEH) methods. An important result is that all the systems react strongly with sodium; at high doping levels two new doping-induced states are detected above the valence band edge of the pristine material. In the case of saturation-doped diphenylpolyenes (i.e., two sodiums per molecule), the new states can be discussed in terms of soliton-antisoliton pairs confined within the polyene part of the molecules; in contrast, the self-localized states induced in PPV and its oligomers have to be referred to as bipolarons.

Place, publisher, year, edition, pages
Elsevier, 1994
Keywords
Spectroscopy, Conjugated molecules and polymers, Gap states
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-124173 (URN)10.1016/0379-6779(94)90015-9 (DOI)A1994PW12000013 ()
Conference
Symposium D on Organic Materials for Electronics - Polymer Interfaces with Metals and Semiconductors, at the 1994 E-MRS Spring Conference, Strasbourg, France, May 24-27, 1994
Available from: 2016-01-20 Created: 2016-01-20 Last updated: 2017-11-30Bibliographically approved
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