| 1. |
- Dupertuis, M A, et al.
(författare)
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Symmetries and the Polarized Optical Spectra of Exciton Complexes in Quantum Dots
- 2011
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 107:12, s. 127403-
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Tidskriftsartikel (refereegranskat)abstract
- A systematic and simple theoretical approach is proposed to analyze true degeneracies and polarized decay patterns of exciton complexes in semiconductor quantum dots. The results provide reliable spectral signatures for efficient symmetry characterization, and predict original features for low C(2 nu) and high C(3 nu) symmetries. Excellent agreement with single quantum dot spectroscopy of real pyramidal InGaAs/AlGaAs quantum dots grown along [111] is demonstrated. The high sensitivity of biexciton quantum states to exact high symmetry can be turned into an efficient uninvasive postgrowth selection procedure for quantum entanglement applications.
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| 2. |
- Karlsson, Fredrik, et al.
(författare)
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Fine structure of exciton complexes in high-symmetry quantum dots: Effects of symmetry breaking and symmetry elevation
- 2010
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Ingår i: PHYSICAL REVIEW B. - : American Physical Society. - 1098-0121. ; 81:16, s. 161307-
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Tidskriftsartikel (refereegranskat)abstract
- Quantum dots (QDs) of high symmetry (e.g., C-3 nu) have degenerate bright exciton states, unlike QDs of C-2 nu symmetry, making them intrinsically suitable for the generation of entangled photon pairs. Deviations from C-3 nu symmetry are detected in real QDs by polarization-resolved photoluminescence spectroscopy in side-view geometry of InGaAs/AlGaAs dots formed in tetrahedral pyramids. The theoretical analysis reveals both an additional symmetry plane and weak symmetry breaking, as well as the interplay with electron-hole and hole-hole exchange interactions manifested by the excitonic fine structure.
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| 3. |
- Karlsson, K Fredrik, et al.
(författare)
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Symmetry Elevation and Symmetry Breaking : Keys to Describe and Explain Excitonic Complexes in Semiconductor Quantum Dots
- 2011
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X.
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Konferensbidrag (refereegranskat)abstract
- The results of a group theoretical analysis of the excitonic fine structure are presented and compared with spectroscopic data on single quantum dots. The spectral features reveal the signatures of a symmetry higher than the crystal symmetry (C 3v ). A consistent picture of the fine structure patterns for various exciton complexes is obtained with group theory and the concepts of symmetry elevation and symmetry breaking.
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| 4. |
- Malafronte, Loredana, 1986, et al.
(författare)
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Combined convective and microwave assisted drying: Experiments and modelling
- 2012
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 112:4, s. 304-312
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Tidskriftsartikel (refereegranskat)abstract
- The drying process is largely used in many different industrial applications, such as treatment of foods,production of cosmetics and pharmaceuticals, manufacturing of paper, wood and building materials,polymers and so on.Physical and mathematical models can constitute useful tools to establish the influence of the main process variables on the final product quality, in order to apply an effective production control. In this work, simulation model was developed to describe combined convective/microwave assisted drying. In particular, a multi-physics approach was applied to take into account heat and two mass balances (for liquid water and for water vapor) and Maxwell’s equations to describe electromagnetic field propagation.Potato matrix was selected as food material; a waveguide with a rectangular cross section, equipped with a hot air circulator device, was used as microwave applicator. The proposed model was found able to describe the process, being thus a useful tool for design and management of the process itself.
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| 5. |
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| 6. |
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| 7. |
- Agekyan, V F, et al.
(författare)
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Effect of a magnetic field on energy transfer of band states to the Mn2+ 3d shell in the CdMgTe matrix with ultrathin CdMnTe layers
- 2010
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Ingår i: PHYSICS OF THE SOLID STATE. - 1063-7834. ; 52:1, s. 27-31
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Tidskriftsartikel (refereegranskat)abstract
- The effect of external magnetic fields on two radiative (band-to-band and on-site) recombination channels in II-VI dilute magnetic semiconductors and related nanostructures has been considered. The 3d on-site emission of manganese ions in CdMgTe matrices containing periodic inclusions of CdMnTe narrow-band-gap layers with thicknesses of 0.5, 1.5, and 3.0 monolayers has been investigated in magnetic fields of up to 6 T. It has been shown that, in a magnetic field, luminescence of manganese ions weakens because of the decrease in the rate of spin-dependent excitation transfer from band states to the Mn2+ 3d shell. The maximum suppression of 3d luminescence has been observed in the matrix with a CdMnTe layer 3.0 monolayers thick. This indicates that the main factor responsible for the energy transfer is the internal field near the CdMnTe layers, which determines the magnetic splitting and spin polarization of band states.
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| 8. |
- Agekyan, V F, et al.
(författare)
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Magnetoluminescence of CdTe/MnTe/CdMgTe heterostructures with ultrathin MnTe layers
- 2011
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Ingår i: Semiconductors (Woodbury, N.Y.). - : MAIK Nauka/Interperiodica (and#1052;and#1040;and#1048;and#1050; and#1053;and#1072;and#1091;and#1082;and#1072;/and#1048;and#1085;and#1090;and#1077;and#1088;and#1087;and#1077;and#1088;and#1080;and#1086;and#1076;and#1080;and#1082;and#1072;). - 1063-7826 .- 1090-6479. ; 45:10, s. 1301-1305
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Tidskriftsartikel (refereegranskat)abstract
- CdTe/MnTe/CdMgTe quantum-well structures with one or two monolayers of MnTe inserted at CdTe/CdMgTe interfaces were fabricated. The spectra of the excitonic luminescence from CdTe quantum wells and their variation with temperature indicate that introduction of ultrathin MnTe layers improves the interface quality. The effect of a magnetic field in the Faraday configuration on the spectral position of the exciton-emission peaks indicates that frustration of magnetic moments in one-monolayer MnTe insertions is weaker than in two-monolayer insertions. The effect of a magnetic field on the exciton localization can be explained in terms of the exciton wave-function shrinkage and obstruction of the photoexcited charge-carrier motion in the quantum well.
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| 9. |
- Aleksandrov, I.A., et al.
(författare)
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Linearly polarized photoluminescence from an ensemble of wurtzite GaN/AlN quantum dots
- 2010
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Ingår i: JETP Letters. - : Springer Science Business Media. - 0021-3640 .- 1090-6487. ; 91:9, s. 452-454
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Tidskriftsartikel (refereegranskat)abstract
- Microphotoluminescence from GaN/AlN quantum dots grown by molecular beam epitaxy on sapphire substrates along the (0001) axis has been studied. To produce quantum dots of different average sizes and densities, the nominal amount of deposited GaN has been varied from 1 to 4 ML. The density of the quantum dots was about 10(11) cm(-2), which corresponded to about 10(3) quantum dots excited in the experiments. The photo-luminescence from the quantum dots was linearly polarized and the maximum polarization degree (15%) has been observed for the sample with the lowest amount of deposited GaN. The photoluminescence intensity from this sample under continuous laser excitation decreased by more than two orders of magnitude for about 30 min and then stabilized. The photoluminescence intensity from other samples under continuous excitation remained constant. We suggest that a rather high polarization degree is caused by anisotropy in the strain and shape of the quantum dots formed near the dislocations, which also act as the centers of nonradiative recombination.
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| 10. |
- Chen, Yen-Ting, et al.
(författare)
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Nucleation of single GaN nanorods with diameters smaller than 35 nm by molecular beam epitaxy
- 2013
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 103:20, s. 203108-
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Tidskriftsartikel (refereegranskat)abstract
- Nucleation mechanism of catalyst-free GaN nanorod grown on Si(111) is investigated by the fabrication of uniform and narrow (andlt; 35 nm) nanorods without a pre-defined mask by molecular beam epitaxy. Direct evidences show that the nucleation of GaN nanorods stems from the sidewall of the underlying islands down to the Si(111) substrate, different from commonly reported ones on top of the island directly. Accordingly, the growth and density control of the nanorods is exploited by a "narrow-pass" approach that only narrow nanorod can be grown. The optimal size of surrounding non-nucleation area around single nanorod is estimated as 88 nm.
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