| 1. |
- Gällström, Andreas, et al.
(författare)
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A defect center for quantum computing : Mo in SiC
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The electronic structure and vibrational properties of molybdenum (Mo) in SiC are analyzed and investigated in detail. Mo is considered as occupying the silicon-carbon divacancy in the so-called asymmetric split vacancy (ASV) configuration. Group-theoretical considerations within this model are used to explain the experimental results (optical properties and behavior in magnetic field). The vibrational properties of the defect are studied using simple the “defect molecule” model with parameters determined phenomenologically from the experimental data. The position of Mo in the ASV configuration deduced from this model is shown to be in good agreement with the earlier reported data from ab initio supercell calculations. The usefulness of molybdenum in SiC in quantum computing is investigated, and it shown that Mo is a highly promising candidate for quantum computing.
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| 2. |
- Gällström, Andreas, et al.
(författare)
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Electronic Configuration of Tungsten in 4H-, 6H-, and 15R-SiC
- 2012
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Ingår i: Materials Science Forum Vols 717 - 720. - : Trans Tech Publications Inc.. - 9783037854198 ; , s. 211-216
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 3. |
- Gällström, Andreas, et al.
(författare)
-
Optical properties and Zeeman spectroscopy of niobium in silicon carbide
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 92:7, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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