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Magnusson, Björn
Publications (10 of 74) Show all publications
Gällström, A., Magnusson, B., Tien Son, N., Ivanov, I. G. & Janzén, E. (2015). Optical identification of intrinsic nearest-neighbor defects in SiC.
Open this publication in new window or tab >>Optical identification of intrinsic nearest-neighbor defects in SiC
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2015 (English)Manuscript (preprint) (Other academic)
Abstract [en]

The optical signature of two types of intrinsic nearest-neighbor defects in SiC is observed in 4H- and 6H-SiC. The first optical signature belong to a defect previously known as UD-2 and identified as the divacancy pair, and the second – to a defect referred to here as UD-0, an unidentified defect. In both these defects, the number of optical centers is equal to the number of possible configurations for nearest-neighbor pairs in the unit cells of these polytypes. The polarization of all optical transitions is investigated. The formation of the two defects by means of electron irradiation and subsequent annealing in samples with different Fermi levels is studied, too. The observed transitions are investigated using group-theoretical analysis and UD-0 is tentatively assigned to the carbon-vacancy carbonantisite pair, based on energy positions of the lines and spin configuration.

National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-117974 (URN)
Available from: 2015-05-19 Created: 2015-05-19 Last updated: 2015-05-19Bibliographically approved
Gällström, A., Magnusson, B., Leone, S., Kordina, O., Son, N. T., Ivády, V., . . . Ivanov, I. G. (2015). Optical properties and Zeeman spectroscopy of niobium in silicon carbide. Physical Review B. Condensed Matter and Materials Physics, 92(7), 1-14, Article ID 075207.
Open this publication in new window or tab >>Optical properties and Zeeman spectroscopy of niobium in silicon carbide
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2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 7, p. 1-14, article id 075207Article in journal (Refereed) Published
Abstract [en]

The optical signature of niobium in the low-temperature photoluminescence spectra of three common polytypes of SiC (4H, 6H, and 15R) is observed and confirms the previously suggested concept that Nb occupies preferably the Si-C divacancy with both Si and C at hexagonal sites. Using this concept we propose a model considering a Nb-bound exciton, the recombination of which is responsible for the observed luminescence. The exciton energy is estimated using first-principles calculation and the result is in very good agreement with the experimentally observed photon energy in 4H SiC at low temperature. The appearance of six Nb-related lines in the spectra of the hexagonal 4H and 6H polytypes at higher temperatures is tentatively explained on the grounds of the proposed model and the concept that the Nb center can exist in both C1h and C3v symmetries. The Zeeman splitting of the photoluminescence lines is also recorded in two different experimental geometries and the results are compared with theory based on phenomenological Hamiltonians. Our results show that Nb occupying the divacancy at the hexagonal site in the studied SiC polytypes behaves like a deep acceptor.

Place, publisher, year, edition, pages
American Physical Society, 2015
National Category
Theoretical Chemistry Other Physics Topics
Identifiers
urn:nbn:se:liu:diva-117972 (URN)10.1103/PhysRevB.92.075207 (DOI)000362204100001 ()
Note

At the time for thesis presentation publication was in status: Manuscript

Funding Agencies|Knut and Alice Wallenberg Foundation; Lendulet program of the Hungarian Academy of Sciences; Hungarian OTKA Project [K101819]; Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; Tomsk State University Academic D. I. Mendeleev Fund Program [8.1.18.2015]

Available from: 2015-05-19 Created: 2015-05-19 Last updated: 2017-12-04Bibliographically approved
Gällström, A., Magnusson, B., Beyer, F., Gali, A., Son, N. ., Leone, S., . . . Janzén, E. (2012). Electronic Configuration of Tungsten in 4H-, 6H-, and 15R-SiC. In: Materials Science Forum Vols 717 - 720: . Paper presented at 14th International Conference on Silicon Carbide and Related Materials (ICSCRM 2011), 11-16 September 2011, Cleveland, OH, USA (pp. 211-216). Trans Tech Publications Inc., 717-720
Open this publication in new window or tab >>Electronic Configuration of Tungsten in 4H-, 6H-, and 15R-SiC
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2012 (English)In: Materials Science Forum Vols 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 211-216Conference paper, Published paper (Refereed)
Abstract [en]

A commonly observed unidentified photoluminescence center in SiC is UD-1. In this report, the UD-1 center is identified to be tungsten related. The identification is based on (i) a W-doping study, the confirmation of W in the samples was made using deep level transient spectroscopy (DLTS), (ii) the optical activation energy of the absorption of UD-1 in weakly n-type samples corresponds to the activation energy of the deep tungsten center observed using DLTS. The tungsten-related optical centers are reported in 4H-, 6H-, and 15R-SiC. Further, a crystal field model for a tungsten atom occupying a Si-site is suggested. This crystal field model is in agreement with the experimental data available: polarization, temperature dependence and magnetic field splitting.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2012
Keywords
deep level defect; PL; transition metal; Crystal Field Model
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-87570 (URN)10.4028/www.scientific.net/MSF.717-720.211 (DOI)000309431000049 ()978-3-03785-419-8 (ISBN)
Conference
14th International Conference on Silicon Carbide and Related Materials (ICSCRM 2011), 11-16 September 2011, Cleveland, OH, USA
Available from: 2013-01-18 Created: 2013-01-18 Last updated: 2015-09-22
Gällström, A., Magnusson, B., Beyer, F., Gali, A., Son Tien, N., Leone, S., . . . Janzén, E. (2012). Optical identification and electronic configuration of tungsten in 4H-and 6H-SiC. Physica. B, Condensed matter, 407(10), 1462-1466
Open this publication in new window or tab >>Optical identification and electronic configuration of tungsten in 4H-and 6H-SiC
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2012 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 407, no 10, p. 1462-1466Article in journal (Refereed) Published
Abstract [en]

Several optically observed deep level defects in SiC are still unidentified and little is published on their behavior. One of the commonly observed deep level defects in semi-insulating SiC is UD-1. less thanbrgreater than less thanbrgreater thanThis report suggests that UD-1 is Tungsten related, based on a doping study and previously reported deep level transient spectroscopy data, as well as photo-induced absorption measurements. The electronic levels involved in the optical transitions of UD-1 are also deduced. The transitions observed in the photoluminescence of UD-1 are from a Gamma(C3v)(4), to two different final states, which transform according to Gamma(C3v)(5)circle plus Gamma(C3v)(6) and Gamma(C3v)(4), respectively.

Place, publisher, year, edition, pages
Elsevier, 2012
Keywords
Deep level defect, PL, Transition metal
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-77521 (URN)10.1016/j.physb.2011.09.062 (DOI)000303149600003 ()
Available from: 2012-05-28 Created: 2012-05-22 Last updated: 2017-12-07
Nguyen, T. S., Carlsson, P., Isoya, J., Morishita, N., Ohshima, T., Magnusson, B. & Janzén, E. (2010). The carbon vacancy related EI4 defect in 4H-SiC. In: Materials Science Forum. Vols. 645-648. Paper presented at ICSCRM2009 (pp. 399-402). Trans Tech Publications, 645-648
Open this publication in new window or tab >>The carbon vacancy related EI4 defect in 4H-SiC
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2010 (English)In: Materials Science Forum. Vols. 645-648, Trans Tech Publications , 2010, Vol. 645-648, p. 399-402Conference paper, Published paper (Refereed)
Abstract [en]

Electron paramagnetic resonance (EPR) was used to study high-purity semi-insulating 4H-SiC irradiated with 2 MeV electrons at room temperature. The EPR signal of the EI4 defect was found to be dominating in samples irradiated and annealed at 750 C. Additional large-splitting Si-29 hyperfine (hf) lines and also other C-13 and Si-29 hf structures were observed. Based on the observed hf structures and annealing behaviour, the complex between a negative carbon vacancy-carbon antisite pair (VCCSi-) and a distance positive carbon vacancy (V-C(+)) is tentatively proposed as a possible model for the EIO4 defect.

Place, publisher, year, edition, pages
Trans Tech Publications, 2010
Keywords
vacancies; antisite; electron irradiation; EPR; hyperfine interaction
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-58212 (URN)10.4028/www.scientific.net/MSF.645-648.399 (DOI)000279657600095 ()
Conference
ICSCRM2009
Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2012-04-03
Carlsson, P., Son, N. T., Magnusson, B., Isoya, J., Morishita, N., Ohshima, T. & Janzén, E. (2010). The EI4 EPR centre in 6H SiC. In: Physica Scripta, Vol. T141. Paper presented at NMR 2009 (pp. 014013). IOP Publishing
Open this publication in new window or tab >>The EI4 EPR centre in 6H SiC
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2010 (English)In: Physica Scripta, Vol. T141, IOP Publishing , 2010, p. 014013-Conference paper, Published paper (Refereed)
Abstract [en]

We present the results of our recent electron paramagnetic resonance (EPR) studies of the EI4 EPR centre in electron-irradiated high-purity semi-insulating 6H SiC. Higher signal intensities and better resolution compared with previous studies have enabled a more detailed study of the hyperfine (hf) structure. Based on the observed hf structure due to the interaction with Si and C neighbours, the effective spin S = 1, the C-1h-symmetry and the annealing behaviour, we suggest a carbon vacancy-carbon antisite complex in the neutral charge state, VCVCCSi0, with the vacancies and the antisite in the basal plane, as a new defect model for the centre.

Place, publisher, year, edition, pages
IOP Publishing, 2010
Series
Physica Scripta, ISSN 0031-8949
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-62776 (URN)10.1088/0031-8949/2010/T141/014013 (DOI)000284694500014 ()
Conference
NMR 2009
Available from: 2010-12-03 Created: 2010-12-03 Last updated: 2011-01-19
Hahn, S., Beyer, F., Gällström, A., Carlsson, P., Henry, A., Magnusson, B., . . . Janzén, E. (2009). Contact-Less Electrical Defect Characterization of Semi-Insulating 6H-SiC Bulk Material. In: Materials Science Forum Vols. 600-603: . Paper presented at 12th International Conference on Silicon Carbide and Related Materials, ICSCRM 2007; Otsu; Japan (pp. 405-408). Trans Tech Publications
Open this publication in new window or tab >>Contact-Less Electrical Defect Characterization of Semi-Insulating 6H-SiC Bulk Material
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2009 (English)In: Materials Science Forum Vols. 600-603, Trans Tech Publications , 2009, p. 405-408Conference paper, Published paper (Refereed)
Abstract [en]

The novel technique microwave detected photo induced current transient spectroscopy (MD-PICTS) was applied to semi-insulating 6H-SiC in order to investigate the properties of inherent defect levels. Defect spectra can be obtained in the similar way to conventional PICTS and DLTS. However, there is no need for contacting the samples, which allows for non-destructive and spatially resolved electrical characterization. This work is focused on the investigation of semi-insulating 6H-SiC grown under different C/Si-ratios. In the corresponding MD-PICTS spectra several shallow defect levels appear in the low temperature range. However the peak assignment needs further investigation. Additionally different trap reemission dynamics are obtained for higher temperatures, which are supposed to be due to different compensation effects.

Place, publisher, year, edition, pages
Trans Tech Publications, 2009
National Category
Natural Sciences Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-41964 (URN)10.4028/www.scientific.net/MSF.600-603.405 (DOI)59424 (Local ID)59424 (Archive number)59424 (OAI)
Conference
12th International Conference on Silicon Carbide and Related Materials, ICSCRM 2007; Otsu; Japan
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2014-10-08
Nguyen, S. T., Carlsson, P., Gällström, A., Magnusson, B. & Janzén, E. (2009). Deep Levels Responsible for Semi-insulating Behaviour in Vanadium-doped 4H-SiC Substrates. In: Materials Science Forum, Vols. 600-603: . Paper presented at 12th International Conference on Silicon Carbide and Related Materials, ICSCRM 2007; Otsu; Japan (pp. 401-404). Trans Tech Publications
Open this publication in new window or tab >>Deep Levels Responsible for Semi-insulating Behaviour in Vanadium-doped 4H-SiC Substrates
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2009 (English)In: Materials Science Forum, Vols. 600-603, Trans Tech Publications , 2009, p. 401-404Conference paper, Published paper (Refereed)
Abstract [en]

Semi-insulating (SI) 4H-SiC substrates doped with vanadium (V) in the range 5.5×1015 –1.1×1017 cm–3 were studied by electron paramagnetic resonance. We show that only in heavily V-doped 4H-SiC vanadium is responsible for the SI behavior, whereas in moderate V-doped substrates with the V concentration comparable or slightly higher than that of the shallow N donor or B acceptor, the SI properties are thermally unstable and determined by intrinsic defects. The results show that the commonly observed thermal activation energy Ea~1.1 eV in V-doped 4H-SiC, which was previously assigned to the single acceptor V4+/3+ level, may be related to deep levels of the carbon vacancy. Carrier compensation processes involving deep levels of V and intrinsic defects are discussed and possible thermal activation energies are suggested.

Place, publisher, year, edition, pages
Trans Tech Publications, 2009
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-41957 (URN)10.4028/www.scientific.net/MSF.600-603.401 (DOI)59416 (Local ID)59416 (Archive number)59416 (OAI)
Conference
12th International Conference on Silicon Carbide and Related Materials, ICSCRM 2007; Otsu; Japan
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2014-09-12
Carlsson, P., Nguyen, S. T., Magnusson, B. & Janzén, E. (2009). Intrinsic Defects in HPSI 6H-SiC: an EPR Study. In: Materials Science Forum, Vols. 600-603: . Paper presented at 12th International Conference on Silicon Carbide and Related Materials, ICSCRM 2007; Otsu; Japan (pp. 381-384). Trans Tech Publications
Open this publication in new window or tab >>Intrinsic Defects in HPSI 6H-SiC: an EPR Study
2009 (English)In: Materials Science Forum, Vols. 600-603, Trans Tech Publications , 2009, p. 381-384Conference paper, Published paper (Refereed)
Abstract [en]

High-purity, semi-insulating 6H-SiC substrates grown by high-temperature chemical vapor deposition were studied by electron paramagnetic resonance (EPR). The carbon vacancy (VC), the carbon vacancy-antisite pair (VCCSi) and the divacancy (VCVSi) were found to be prominent defects. The (+|0) level of VC in 6H-SiC is estimated by photoexcitation EPR (photo-EPR) to be at ~ 1.47 eV above the valence band. The thermal activation energies as determined from the temperature dependence of the resistivity, Ea~0.6-0.7 eV and ~1.0-1.2 eV, were observed for two sets of samples and were suggested to be related to acceptor levels of VC, VCCSi and VCVSi. The annealing behavior of the intrinsic defects and the stability of the SI properties were studied up to 1600°C.

Place, publisher, year, edition, pages
Trans Tech Publications, 2009
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-41959 (URN)10.4028/www.scientific.net/MSF.600-603.381 (DOI)59418 (Local ID)59418 (Archive number)59418 (OAI)
Conference
12th International Conference on Silicon Carbide and Related Materials, ICSCRM 2007; Otsu; Japan
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2014-09-12
Gällström, A., Magnusson, B. & Janzén, E. (2009). Optical identification of Mo related deep level defect in 4H and 6H SiC. In: Materials Science Forum Vols. 615-617: . Paper presented at 7th European Conference on Silicon Carbide and Related Materials (pp. 405-408). Trans Tech Publications
Open this publication in new window or tab >>Optical identification of Mo related deep level defect in 4H and 6H SiC
2009 (English)In: Materials Science Forum Vols. 615-617, Trans Tech Publications , 2009, p. 405-408Conference paper, Published paper (Refereed)
Abstract [en]

The photoluminescence (PL) from the I 1 centre is observed in p-, n-type as well as in compensated samples, using above band gap excitation. The PL from I 1 in the two polytypes 4H and 6H is very similar, the difference being the position of the main peak, in 4H 1.1521 eV and 1.1057 eV in 6H. We here suggest I-1 to be Mo related based on intentional doping, SIMS results and comparison with earlier reports of Mo in SiC using magnetic resonance techniques. From PL measurements, we analyze the electron structure of the defect, and suggest it be the neutral Mo (4d2) residing on a Si site, the luminescence coming from the transition between the 3A2 multiplet of the first excited electronic configuration and the ground state 3A2.

Place, publisher, year, edition, pages
Trans Tech Publications, 2009
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-43529 (URN)10.4028/www.scientific.net/MSF.615-617.405 (DOI)74089 (Local ID)74089 (Archive number)74089 (OAI)
Conference
7th European Conference on Silicon Carbide and Related Materials
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2014-08-27
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