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| 2. |
- Arwin, Hans, 1950-, et al.
(författare)
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Enhancement in ellipsometric thin film sensitivity near surface plasmon resonance conditions
- 2008
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley-VCH Verlagsgesellschaft. - 1862-6300 .- 1862-6319. ; 205:4, s. 817-820
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Tidskriftsartikel (refereegranskat)abstract
- Ellipsometry used in internal reflection mode exhibits enhanced thin film sensitivity if operated close to surface plasmon resonance conditions. Compared to conventional ellipsometry, the changes in the ellipsometric parameter Δ are several orders of magnitude larger. Here, the origin of this large sensitivity is discussed by analysing thin film approximations of the complex reflectance ratio. It is found that the thickness sensitivity in Δ is proportional to the inverse of the difference between the intrinsic and the radiation-induced damping of the surface plasmons.
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| 3. |
- Blumenau, A.T., et al.
(författare)
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The effect of charge on kink migration at 90° partial dislocations in SiC
- 2005
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 202:5, s. 877-882
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Tidskriftsartikel (refereegranskat)abstract
- SiC bipolar devices show a degradation under forward-biased operation which has been linked with a recombination enhanced motion of one of the two glide dislocations having either Si or C core atoms. We have carried out calculations of the core structures and dynamics of partial dislocations in 3C and 2H-SiC using the density functional based codes DFTB and AIMPRO. After in earlier theoretical work we reported on the structure, energetics and electronic activity of both of the Shockley partials, and on the formation and migration barriers of kinks, in this work we present first results on the effect of charge on the disloction kinks. The calculations give insights into the device degradation mechanism.
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| 4. |
- Buyanova, Irina A., et al.
(författare)
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Optical and electronic properties of GaInNP alloys - a new material system for lattice matching to GaAs
- 2008
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 205:1, s. 101-106
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we will review our recent results from optical characterization studies of GaInNP. We will show that N incorporation in these alloys affects their structural and defect properties, as well as the electronic structure. The main structural changes include (i) increasing carrier localization due to strong compositional fluctuations, which is typical for all dilute nitrides, and (ii) N-induced long range ordering effects, specific for GaInNP. The observed degradation of radiative efficiency of the alloys upon increasing N content is attributed to formation of several defects acting as centres of efficient non-radiative recombination. One of the defects is identified as a complex involving a Ga interstitial atom. N incorporation is also found to change the band line up from the type I in the GaInP/GaAs structures to the type 11 in the GaInNP/GaAs heterojunctions with [N] > 0.5%. For the range of N compositions studied ([N] <= 2%), a conduction band offset at the GaInNP/GaAs interface is found to nearly linearly depend on [N] at -0.10 eV/%, whereas the valence band offset remains unaffected. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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| 5. |
- Carva, Karel, et al.
(författare)
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Spin-mixing conductances : The influence of disorder
- 2008
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Ingår i: Physica status solidi A, Applications and materials science. - : Wiley. - 1862-6300. ; 205:8, s. 1805-1808
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Tidskriftsartikel (refereegranskat)abstract
- Spin transfer torque exerted on a magnetic layer can be viewed as a linear response to the spin accumulation inside an adjacent non-magnetic layer, information about their response coefficient is provided by the complex spin-mixing conductance C-mix. Substitutional disorder is known to affect the spin-dependent charge conductances and often reduces strongly the magnetoresistance. Here, we examine its impact on C-mix of several selected realistic systems. Recently predicted oscillations of C-mix as a function of ferromagnetic layer thickness in Ni based junctions might be suppressed by interface interdiffusion, but presented ab initio calculations disprove this possibility. Halfmetallic character of the Heusler compound Co(2)Mnsi is destroyed by often encountered antisite disorder; however the impact of this disorder to the predicted C-mix is rather weak. Diluted magnetic semiconductor (Ga,Mn)As is an intrinsically disordered system the analysis of calculations shows that the variation of C-mix with substitutional Mn content can be understood in terms of the associated change of the number of carriers, whereas the variation with lattice defects is more complex.
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| 6. |
- Darakchieva, Vanya
(författare)
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Infrared generalized ellipsometry on non-polar and superlattice group-III nitride films : Strain and phonon anisotropy
- 2008
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Ingår i: Physica Status Solidi (A) Applications and Materials. - : Wiley. - 1862-6300. ; 205:4, s. 905-913
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Tidskriftsartikel (refereegranskat)abstract
- This contribution reviews the application of generalized infrared spectroscopic ellipsometry (GIRSE) to studies of optical phonons in heteroepitaxial wurtzite GaN films with a-plane orientation and c-plane Al(Ga)N/GaN superlattices. We demonstrate the capability of GIRSE to detect spectrally narrow dichroism, caused by anisotropic strain in non-polar oriented films thereby allowing a precise location of the phonon mode resonances for different polarizations. A distinct correlation between anisotropic strain components, which have been independently asessed by high-resolution X-ray diffraction, and phonon frequencies reveal the phonon deformation potentials. Further, GIRSF is shown to be a valuable tool in identification of superlattice phonon modes and their character. The frequency shifts of the superlattice modes with respect to the strain-free positions are analyzed versus strain and composition in order to assess the mode suitability for estimation of strain, polarization doping, and composition for the individual layers in complex device heterostructures. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.
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| 8. |
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| 9. |
- Fujita, N., et al.
(författare)
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Core reconstructions of the (100) edge dislocation in single crystal CVD diamond
- 2007
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 204:7, s. 2211-2215
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Tidskriftsartikel (refereegranskat)abstract
- Dislocations are common defects in both natural as well as in CVD-grown diamond. Recent advances in the growth of high quality single crystal CVD diamond have led to an increased interest in the atomistic and electronic structure of 100 dislocations. These dislocations are observed as mixed-type 45° and pure edge dislocations. Previously we investigated both types and found that the 45° is by far lower in core energy than the proposed structure of the edge type. In this work we focus on the straight 100 dislocation only and present novel core reconstructions. We find a minimum energy structure for the edge-type dislocation which has a similar core energy as the mixed-type dislocation.
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| 10. |
- Fujita, N, et al.
(författare)
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Theoretical studies on 100 dislocations in single crystal CVD diamond
- 2006
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Ingår i: Physica status solidi A. - Weinheim : Wiley-VCH Verlagsgesellschaft. - 1862-6300 .- 1862-6319. ; , s. 3070-3075
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Konferensbidrag (refereegranskat)abstract
- Dislocations are common defects in both natural as well as in CVD-grown diamond. Recent advances in the growth of high quality single crystal CVD diamond have led to an increased interest in the atomistic and electronic structure of < 100 > dislocations. These dislocations are observed as mixed-type 45 degrees and pure edge dislocations. Hence in this work we present ab initio modelling studies on these two types of dislocations. The 45 degrees dislocation is found to be by far more stable than the pure edge and both dislocations lead to states in the electronic band gap. An alternative structure for the mixed-type dislocation, which is not straight but kinked and consists of short edge and screw segments, was found slightly higher in energy than the straight structure.
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