| 1. |
- Dagnelund, Daniel, 1980-, et al.
(författare)
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Evidence for a phosphorus-related interfacial defect complex at a GaP/GaNP heterojunction
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : The American Physical Society. - 1098-0121 .- 1550-235X. ; 81, s. 115334-
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Tidskriftsartikel (refereegranskat)abstract
- Optically detected magnetic resonance (ODMR) studies of molecular beam epitaxial GaNP/GaP structures reveal presence of a P-related complex defect, evident from its resolved hyperfine interaction between an unpaired electronic spin (S=1/2) and a nuclear spin (I = ½) of a 31P atom. The principal axis of the defect is concluded to be along a <111> crystallographic direction from angular dependence of the ODMR spectrum, restricting the P atom (either a PGa antisite or a Pi interstitial) and its partner in the complex defect to be oriented along this direction. The principal values of the electronic g-tensor and hyperfine interaction tensor are determined as: g┴=2.013, g║=2.002, and A┴=130´10-4 cm-1, A║=330´10-4 cm-1, respectively. The interface nature of the defect is clearly manifested by the absence of the ODMR lines originating from two out of four equivalent <111> orientations. Defect formation is shown to be facilitated by nitrogen ion bombardment under non-equilibrium growth conditions and the defect is thermally stable upon post-growth thermal annealing.
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| 2. |
- Rudko, G.Yu, et al.
(författare)
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Optically detected magnetic resonance study of relaxation/emission processes in the nanoparticle-polymer composite
- 2019
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Ingår i: SPQEO. - Kiev, Ukraine : Natsional'na Akademiya Nauk Ukrainy * Instytut Fizyky Napivprovidnykiv. - 1605-6582. ; 22:3, s. 310-318
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Tidskriftsartikel (refereegranskat)abstract
- Two nanocomposites containing CdS nanoparticles in polymeric matrices were studied using the photoluminescence (PL) and optically detected magnetic resonance (ODMR) methods. Due to equal sizes of NPs in the composites (~5 nm) but different matrices – the oxygen-containing polymer PVA (polyvinyl alcohol) and oxygen-free polymer PEI (polyethyleneimine) – differences of nanocomposites properties are predominantly caused by different interfacial conditions. ODMR spectra have revealed five types of centers related to the PL emission – four centers involved in radiative recombination and one center related to non-radiative recombination processes. The oxygen-related interfacial center in CdS/PVA (LK1-center) and sulfur vacancy center in CdS/PEI (Vs-center) were identified.
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| 3. |
- Toropov, A. A., et al.
(författare)
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InAs/Zn(Mn)Te/Cd(Mn)Se pseudomorphic quantum well structures for spintronic applications
- 2004
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Ingår i: 11th International Conference on II-VI Compounds,2003. - : WileyVCH. ; , s. 704-
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Konferensbidrag (refereegranskat)abstract
- Zn(Mn)Te/Cd(Mn)Se quantum well heterostructures have been grown pseudomorphically on InAs(001) substrates using original InAs surface preparation techniques. The structures demonstrated bright PL in the 1-1.3 eV range and the effect of giant Zeeman splitting in the external magnetic field.
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| 4. |
- Tveritinova, E. A., et al.
(författare)
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Effect of the detonation nanodiamond surface on the catalytic activity of deposited nickel catalysts in the hydrogenation of acetylene
- 2013
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Ingår i: Russian Journal of Physical Chemistry. - : SP MAIK Nauka/Interperiodica. - 0036-0244 .- 1531-863X. ; A 87:7, s. 1114-1120
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Tidskriftsartikel (refereegranskat)abstract
- A comparative study is performed of the catalytic activity of nanosized nickel deposited on deto nation synthesis nanodiamond (DND) and coal (CSUG) produced by burning sugar and crystalline quartz in the hydrogenation of acetylene. Nanosized nickel is obtained through the thermal decomposition of nickel formate under a dynamic vacuum. The catalysts are studied by means of scanning electron and transmission electron microscopy, Xray fluorescence, IRspectroscopy, Xray diffraction, and pulse microcatalytic method. It is shown that Ni/DND is an active catalyst of acetylene hydrogenation, considerably surpassing Ni/quartz and Ni/CSUG. The apparent activation energy of the hydrogenation of acetylene is calculated, and the region of the reaction are determined for all catalysts. It is found that the influence of the structure and nature of a functional coating of nanodiamond on the catalytic activity of Ni/DND deposited catalyst in the hydrogenation of acetylene. The ability of Ni/DND to hold active hydrogen is detected.
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| 5. |
- Dagnelund, Daniel, et al.
(författare)
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Carrier and Spin Injection from ZnMnSe to CdSe Quantum Dots
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Optical carrier/exction and spin injection processes from a ZnMnSe dilute magnetic semiconductor (DMS) to CdSe quantum dots (QD’s) are studied in detail by means of spinpolarized magneto- photoluminescence (PL) and PL excitation spectroscopies. Efficiency of carrier/exciton transfer is found to be practically independent of width (Lb) of a ZnSe barrier layer inserted between the DMS and QD’s. This is tentatively explained in terms of photonexchange energy transfer. In sharp contrast, spin injection efficiency is found to be largely suppressed in the structures with large Lb, pointing towards increasing spin loss.
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| 6. |
- Tveritinova, E A, et al.
(författare)
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Catalytic conversion of C(2)-C(3) alcohols on detonation nanodiamond and its modifications
- 2012
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Ingår i: Russian Journal of Physical Chemistry. - : MAIK Nauka/Interperiodica. - 0036-0244 .- 1531-863X. ; 86:1, s. 26-31
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic activity of detonation nanodiamond and its modifications obtained through treatment with hydrogen or air at elevated temperatures is studied in the conversion of C(2)-C(3) alcohols. The catalysts were characterized by means of electron microscopy, optical (FTIR) spectroscopy, elemental analysis and pulse microcatalytic method. It has been established that nanodiamond exhibits high catalytic activity in the conversion of alcohols. The oxidizing and reducing treatment of nanodiamond changes its activity and selectivity, and the activity of oxidized nanodiamond is considerably higher than that of reduced nanodiamond.
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| 7. |
- Dagnelund, Daniel, 1980-, et al.
(författare)
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Activation of defects in GaNP by post-growth hydrogen treatment
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Effect of post-growth hydrogen treatment on defects and their role in carrier recombination in molecular beam epitaxial GaNP alloys is examined by means of photoluminescence and optically detected magnetic resonance. We present direct experimental evidence for effective activation of several different defects in carrier recombination by the hydrogen treatment. Among them, two defect complexes are identified to contain a Ga interstitial (Gai). None of the activated Gai complexes was previously observed in GaNP. Possible mechanisms for the hydrogen-induced defect activation are discussed.
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| 8. |
- Dagnelund, Daniel, et al.
(författare)
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Magneto-optical and tunable laser excitation spectroscopy of spin-injection and spin loss from Zn(Cd)MnSe diluted magnetic quantum well to CdSe non-magnetic quantum dots
- 2008
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Konferensbidrag (refereegranskat)abstract
- Magneto-optical spectroscopy in combination with tunable laser spectroscopy is employed to study the effect of sample design on optical spin-injection efficiency from a Zn(Cd)MnSe diluted magnetic semiconductor (DMS) into non-magnetic CdSe quantum dots (QDs). Two samples with inverted growth sequence of the DMS and QD layers were grown for this purpose. Despite observation of clear evidence for exciton/carrier-injection from the DMS to the QDs in both structures, their spin-injection efficiency is markedly different. The structure grown with the QD layer topmost exhibits rather efficient spin-injection, while the structure grown with the DMS layer topmost does not show any sign of spin-injection. Even in the former case, the spin-polarization of the injected excitons/carriers is deduced to be about 32%, decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin-injection across the heterointerfaces. © 2007 Elsevier B.V. All rights reserved.
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| 9. |
- Ji, Fuxiang, 1991-, et al.
(författare)
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Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl6
- 2023
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Ingår i: Advanced Optical Materials. - : Wiley-Blackwell. - 2162-7568 .- 2195-1071.
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron–phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK−1 based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III–V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.
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| 10. |
- Ji, Fuxiang, 1991-, et al.
(författare)
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Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl6
- 2024
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Ingår i: Advanced Optical Materials. - : John Wiley & Sons. - 2162-7568 .- 2195-1071. ; 12:8
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron-phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK(-1) based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III-V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.
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