| 1. |
- Suchodolskis, A., et al.
(författare)
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Photoemission and optical spectroscopy of i-ZnMgEr quasicrystal
- 2005
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Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 107:2, s. 412-419
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Tidskriftsartikel (refereegranskat)abstract
- The results of photoemission and optical studies of icosahedral single-grain ZnMgEr quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10(-10) mbar pressure and low, 140-150 K temperature. The valence band photoemission spectra measured reveal a simple metal-type valence band of icosahedral ZnMgEr with a distinct Fermi edge cut-off and with a sharp pseudogap feature. The photoemission spectra of shallow Mg 2p and Zn 3d core levels indicate a coordination shift of Mg 2p spin-orbit doublet and an oscillating dependence of Zn 3d photoemission line components on the photon energy within the hv = 20-160 eV range investigated. The optical response of icosahedral ZnMgEr, a dispersion of the dielectric function, was measured by the spectroscopic ellipsometry technique in the 0.5-5.0 eV spectral range. The optical spectra of the quasicrystal indicate the Drude-type optical response superimposed with a peak of interband optical transitions. The interband optical transitions can be modelled with the pseudogap parameters which agree with those deduced in an analysis of the photoemission valence band spectra.
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| 2. |
- Karpus, V., et al.
(författare)
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Coordination-induced structure of the Mg 2p core level in i-ZnMgR quasicrystals
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:15
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed analysis of Mg 2p photoemission (PE) spectra in icosahedral ZnMgR (R=Y, Ho, Er) quasicrystals and in the crystalline Zn2Mg Laves phase. Synchrotron-radiation PE measurements were performed on in situ cleaved single-grain samples at 10(-10) mbar pressure and low, 90-150 K, temperature. The analysis of Mg 2p PE spectra in Zn2Mg reveals a surface shift of the core level of -0.12 eV. The Mg 2p PE spectra in i-ZnMgR quasicrystals are essentially broadened as compared to spectra in Zn2Mg Laves phase. The effect is due to the coordination-induced structure of the Mg 2p levels. Different local surroundings of Mg atoms in quasicrystals induce both different shifts of the Mg 2p level and splittings of its spin-orbit components. The local coordination potential at different Mg sites in the quasicrystalline lattice is calculated on the basis of the face-centered icosahedral ZnMgY atomic structure data, recently determined from the pair distribution function analysis. The coordination shifts calculated are spread within an interval of about 0.3 eV, while the splittings of the 2p(3/2) component are of the order of 1-10 meV. The simulated theoretical Mg 2p PE spectra of fci-ZnMgR quasicrystals perfectly fit the experimental data.
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| 3. |
- Karpus, V, et al.
(författare)
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Optical spectroscopy and electronic structure of the face-centered icosahedral quasicrystals Zn-Mg-R (R=Y, Ho, Er)
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 88:9
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Tidskriftsartikel (refereegranskat)abstract
- Results of optical spectroscopy studies of the face-centered icosahedral (fci) single-grain Zn-Mg-Y, Zn-Mg-Ho, and Zn-Mg-Er quasicrystals (QCs) are presented. The dielectric function of the QCs was measured in the 0.01–6 eV spectral range by IR-UV spectroscopic ellipsometry and far infrared reflection spectroscopy techniques. A theoretical scheme of optical conductivity calculations is extended to account for the Fermi level positions within and below a pseudogap. The model of the QC electron energy spectrum, based on a band structure hypothesis, is suggested, which treats the electronic subsystem as a nearly free electron gas affected by intersections of the Fermi surface with several families of Bragg planes. The experimental optical spectra are reproduced in detail by theoretical calculations carried out within the framework of the model. The parameters of the electron energy spectrum deduced from an analysis of optical data are close to those previously determined in an analysis of fci Zn-Mg-R valence band photoemission spectra.
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| 4. |
- Suchodolskis, A., et al.
(författare)
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Indication of van Hove singularities in the density of states of ZnMg(Y,Ho) quasicrystals
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 68:5
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Tidskriftsartikel (refereegranskat)abstract
- We present a low-temperature synchrotron-radiation photoelectron microspectroscopy study of the valence bands of single-grain icosahedral ZnMgY and ZnMgHo quasicrystals. Their valence band photoemission spectra reveal in both cases a simple metal-type behavior with a clear metallic Fermi edge and a sharp pseudogap feature: the spectral intensity exhibits a maximum at approximate to0.7 eV below the chemical potential and a subsequent decrease as the Fermi level is approached. The analysis of the pseudogap feature, based on the band-structure hypothesis, shows that it corresponds to the van Hove singularities in the density of states (DOS), which originate from the intersections of the isoenergetic surface with the 222100 and 311111 Bragg planes. The reconstructed density of states agrees in general trends with the theoretical first-principles DOS of hexagonal ZnMgY approximants, and correctly reproduces the experimental value of i-ZnMgY electronic specific-heat coefficient.
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| 5. |
- Suchodolskis, A., et al.
(författare)
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Ion implantation damage annealing in 4H-SiC monitored by scanning spreading resistance microscopy
- 2006
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:2, s. 611-614
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Tidskriftsartikel (refereegranskat)abstract
- To obtain a better understanding of the damage annealing process and dopant defect incorporation and activation we have implanted epitaxially grown 4H-SiC layers with high doses of Al+ ions. Cross-sections of the samples are investigated by scanning spreading resistance microscopy (SSRM) using a commercial atomic force microscopy (AFM). The defects caused by the implanted ions compensate for the doping and decrease the charge carrier mobility. This causes the resistivity to increase in the as-implanted regions. The calculated profile of implanted ions is in good agreement with the measured ones and shows a skewed Gaussian shape. Implanted samples are annealed up to 400 degrees C. Despite these low annealing temperatures we observe a clear improvement of the sample conductivity in the asimplanted region.
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| 6. |
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| 7. |
- Suchodolskis, A., et al.
(författare)
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Pseudogap structure in icosahedral ZnMgY and ZnMgHo quasicrystals
- 2003
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 212, s. 485-490
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Tidskriftsartikel (refereegranskat)abstract
- The results of a photoemission study of icosahedral single-grain ZnMg(Y, Ho) quasicrystals and their crystalline approximant Zn2Mg are presented. Synchrotron radiation photoemission measurements have been performed on in situ cleaved samples at low temperature of approximate to90 K and 10(-10) mbar pressure. The spectra obtained indicate simple metal-type valence bands (VB) with distinct Fermi edge cutoff. Analysis of the Fermi edge spectra reveals the presence of a pseudogap in i-ZnMg(Y, Ho) quasicrystals. The pseudogap corresponds to a rather sharp DOS dip at the Fermi level with th approximate to50% (of the normal DOS) depth and the approximate to0.8 eV width. The values of i-ZnMg(Y, Ho) pseudogap parameters are comparable with those of other quasicrystals.
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| 8. |
- Suchodolskis, A., et al.
(författare)
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Valence band structure of i-ZnMgEr quasicrystal : photoemission study
- 2004
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 16:50, s. 9137-9142
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Tidskriftsartikel (refereegranskat)abstract
- The results of photoemission study of icosahedral single-grain ZnMgEr quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10(-10) mbar pressure and low, 140-150 K, temperature. The valence band photoemission spectra measured reveal a simple-metal type valence band of i-ZnMgEr with a distinct Fermi edge cutoff and a spectral feature at 0.7 eV below epsilon(F). Analysis of the PE spectra shows that the spectral feature observed corresponds to the van Hove singularities in the density of states, which are due to intersections of the Fermi surface with the 222100 and 311111 Bragg planes.
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