| 1. |
- Adam, Rania Elhadi, 1978-, et al.
(författare)
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Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities
- 2019
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Ingår i: RSC Advances. - Cambridge : Royal Meteorological Society. - 2046-2069. ; 9:52, s. 30585-30598
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Tidskriftsartikel (refereegranskat)abstract
- High-efficiency photocatalysts are crucial for the removal of organic pollutants and environmental sustainability. In the present work, we report on a new low-temperature hydrothermal chemical method, assisted by ultrasonication, to synthesize disruptive plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis. The plasmonic nanocomposites were investigated by a wide range of characterization techniques, confirming successful formation of photocatalysts with excellent degradation efficiency. Using Congo red as a model dye molecule, our experimental results demonstrated a photocatalytic reactivity exceeding 90% efficiency after one hour simulated solar irradiation. The significantly enhanced degradation efficiency is attributed to improved electronic properties of the nanocomposites by hybridization of the graphene and to the addition of Ag/AgI which generates a strong surface plasmon resonance effect in the metallic silver further improving the photocatalytic activity and stability under solar irradiation. Scavenger experiments suggest that superoxide and hydroxyl radicals are responsible for the photodegradation of Congo red. Our findings are important for the fundamental understanding of the photocatalytic mechanism of ZnO/graphene/Ag/AgI nanocomposites and can lead to further development of novel efficient photocatalyst materials.
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| 2. |
- Adam, Rania Elhadi, 1978-, et al.
(författare)
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Synthesis of Mg-doped ZnO NPs via a chemical low-temperature method and investigation of the efficient photocatalytic activity for the degradation of dyes under solar light
- 2020
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Ingår i: Solid State Sciences. - : Elsevier. - 1293-2558 .- 1873-3085. ; 99
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Tidskriftsartikel (refereegranskat)abstract
- Doped semiconductors nanostructures (NSs) have shown great interest as a potential for green and efficient photocatalysis activities. Magnesium (Mg)-doped zinc oxide (ZnO) nanoparticles (NPs) has been synthesized by a one-step chemical low temperature (60 °C) co-precipitation method without further calcination and their photocatalytic performance for photodegradation of Methylene blue (MB) dye under the illumination of solar light is investigated. The crystal structure of the synthesized NPs is examined by X-ray diffraction (XRD). XRD data indicates a slight shift towards higher 2θ angle in Mg-doped samples as compared to the pure ZnO NPs which suggest the incorporation of Mg2+ into ZnO crystal lattice. X-ray photoelectron spectroscopy (XPS), UV–Vis spectrophotometer and cathodoluminescence (CL) spectroscopy, were used to study electronics, and optical properties, respectively. The XPS analysis confirms the substitution of the Zn2+ by the Mg2+ into the ZnO crystal lattice in agreement with the XRD data. The photocatalytic activities showed a significant enhancement of the Mg-doped ZnO NPs in comparison with pure ZnO NPs. Hole/radical scavengers were used to reveal the mechanism of the photodegradation. It was found that the addition of the Mg to the ZnO lattices increases the absorption of the hydroxyl ions at the surface of the NPs and hence acts as a trap site leading to decrease the electron-hole pair and consequently enhancing the photodegradation.
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| 3. |
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| 4. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Band alignment in the GaNAs/GaAs quantum structures
- 2001
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Konferensbidrag (refereegranskat)abstract
- The band alignment in the GaN_xAs_1-x/GaAs quantum well (QW) structures with low N composition is studied by employing time-resolved photoluminescence (PL) spectroscopy, PL polarization measurements and optically-detected cyclotron resonance (ODCR) studies. The type I band line-up is concluded based on the following experimental results. Firstly, radiative lifetime of the near band gap PL emission in the GaNAs/GaAs MQW structures is nearly identical to that for the spatially direct PL transitions in the GaNAs epilayers. Secondly, the observed polarization of the PL emission in GaNAs QWs (preferentially along the growth direction) is more consistent with the type I band line-up in the GaNAs/GaAs QWs. Thirdly, since the ODCR peaks arising from the free electrons and free holes in GaAs disappear under resonant excitation of the GaNAs MQWs, the photo-excited holes are spatially confined within the GaNAs layers under the resonant excitation condition.
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| 5. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Evidence for type I band alignment in GaNAs/GaAs quantum structures by optical spectroscopies
- 2002
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier. - 1386-9477 .- 1873-1759. ; 13:2-4, s. 1074-1077
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Tidskriftsartikel (refereegranskat)abstract
- Type I band line-up in GaNxAs1−x/GaAs multiple quantum wells (MQW) with xless-than-or-equals, slant3% is concluded based on the following experimental results: (i) a comparable radiative decay time of the GaNAs-related photoluminescence (PL) measured from single GaNAs epilayers and the GaNAs/GaAs MQW structures, (ii) the observed PL polarization, and (iii) the spatial confinement of photoexcited holes within the GaNAs layers under resonant excitation of the GaNAs MQW.
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| 6. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Mechanism for Light Emission in GaNAs/GaAs Structures Grown by Molecular Beam Epitaxy
- 1999
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Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 216:1, s. 125-129
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Tidskriftsartikel (refereegranskat)abstract
- A detailed photoluminescence (PL) study reveals that the low-temperature PL emission in GaNAs epilayers and GaAs/GaNxAs1 - x quantum well structures grown by molecular beam epitaxy is governed by recombination of localized excitons. This conclusion is based on the analysis of the PL lineshape, its dependence on the excitation power and measurement temperature, as well as PL transient data. The depth of the localization potential is estimated as about 60 meV, varying slightly among the different structures.
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| 7. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Mechanism for low-temperature photoluminescence in GaNAs/GaAs structures grown by molecular-beam epitaxy
- 1999
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 75:4, s. 501-
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism for low-temperature photoluminescence (PL) emissions in GaNAs epilayers and GaAs/GaNxAs1 - x quantum well (QW) structures grown by molecular-beam epitaxy is studied in detail, employing PL, PL excitation, and time-resolved PL spectroscopies. It is shown that even though quantum confinement causes a strong blueshift of the GaNAs PL emission, its major characteristic properties are identical in both QW structures and epilayers. Based on the analysis of the PL line shape, its dependence on the excitation power and measurement temperature, as well as transient data, the PL emission is concluded to be caused by a recombination of excitons trapped by potential fluctuations in GaNAs.
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| 8. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Mechanism for radiative recombination in ZnCdO alloys
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:26
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Tidskriftsartikel (refereegranskat)abstract
- Temperature dependent cw- and time-resolved photoluminescence combined with absorption measurements are employed to evaluate the origin of radiative recombination in ZnCdO alloys grown by molecular-beam epitaxy. The near-band-edge emission is attributed to recombination of excitons localized within band tail states likely caused by nonuniformity in Cd distribution. Energy transfer between the tail states is argued to occur via tunneling of localized excitons. The transfer is shown to be facilitated by increasing Cd content due to a reduction of the exciton binding energy and, therefore, an increase of the exciton Bohr radius in the alloys with a high Cd content. © 2007 American Institute of Physics.
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| 9. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Mechanism for rapid thermal annealing improvements in undoped GaNxAs1-x/GaAs structures grown by molecular beam epitaxy
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 77:15, s. 2325-
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Tidskriftsartikel (refereegranskat)abstract
- A systematic investigation of the effect of rapid thermal annealing (RTA) on optical properties of undoped GaNAs/GaAs structures is reported. Two effects are suggested to account for the observed dramatic improvement in the quality of the GaNxAs1-x/GaAs quantum structures after RTA: (i) improved composition uniformity of the GaNxAs1-x alloy, deduced from the photoluminescence (PL), PL excitation and time-resolved measurements; and (ii) significant reduction in the concentration of competing nonradiative defects, revealed by the optically detected magnetic resonance studies.
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| 10. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Optical and electronic properties of GaNAs/GaAs structures
- 2000
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Konferensbidrag (refereegranskat)abstract
- We review our recent results from studies of electronic properties of GaNAs/GaAs structures with low nitrogen content, by photoluminescence (PL), PL excitation, time-resolved PL spectroscopies as well as optically detected magnetic resonance (ODMR) and cyclotron resonance (ODCR) studies. The issues to be addressed include key material-related properties and fundamental electronic parameters of the GaNAs alloy, relevant to device applications, such as identification of the dominant recombination processes in the alloy, compositional dependence of the electron effective mass and band alignment in the GaNAs/GaAs heterostructures.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Time-resolved studies of photoluminescence in GaNxP1-x alloys : Evidence for indirect-direct band gap crossover
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:1, s. 52-
-
Tidskriftsartikel (refereegranskat)abstract
- Time resolved photoluminescence spectroscopy is employed to monitor the effect of N incorporation on the band structure of GaNP alloys. Abrupt shortening in radiative lifetime of near-band gap emissions, arising from excitonic radiative recombination within N-related centers, is found to occur at very low N compositions of around 0.5%, i.e., within the same range as the appearance of the direct-band gap-like transitions in the photomodulated transmission spectra of GaNP reported previously. The effect has been attributed to an enhancement in oscillator strength of optical transitions due to band crossover from indirect to direct-band gap of the alloy.
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| 15. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Type I band alignment in the GaNxAs1-x/GaAs quantum wells
- 2001
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 63:3, s. 333031-333034
-
Tidskriftsartikel (refereegranskat)abstract
- Three independent experimental techniques, namely, time-resolved photoluminescence (PL) spectroscopy, PL polarization, and optically detected cyclotron resonance, are employed to determine the band alignment of GaNxAS1-x/GaAs quantum structures with a low-N composition. It is concluded that band lineup is type I based on the following experimental results: (i) comparable radiative decay time of the GaNAs-related emission measured from single GaNAs epilayers and from GaNAs/GaAs quantum well (QW) structures, (ii) polarization of the GaNAs-related emission, and (iii) spatial confinement of the photoexcited holes within the GaNAs layers under resonant excitation of the GaNAs QW's.
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| 16. |
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| 17. |
- Choubina, Tatiana, 1950-, et al.
(författare)
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The slow light in GaN
- 2008
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Ingår i: ICPS2008,2008. ; , s. 647-
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Konferensbidrag (refereegranskat)
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Hemmingsson, Carl, 1964-, et al.
(författare)
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Growth of bulk GaN in a vertical hydride vapour phase epitaxy reactor
- 2006
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 40:4-6 SPEC. ISS., s. 205-213
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Tidskriftsartikel (refereegranskat)abstract
- Using the hydride vapour phase epitaxy technique, we have grown 2-inch diameter bulk GaN material with a thickness up to 2 mm. The growth was performed in a vertical hot-walled reactor at atmospheric pressure. In this geometry, the process gases are distributed from the bottom upwards through the reactor. We present recent results on growth and characterization of the bulk GaN material. The structural and optical properties of the layers have been studied using decorative etching, optical microscopy, scanning electron microscopy, X-ray diffraction, cathodoluminescence, and low temperature photoluminescence. © 2006 Elsevier Ltd. All rights reserved.
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| 23. |
- Honda, Y., et al.
(författare)
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DAP emission band in a carbon doped (1-101)GaN grown ob (001) Si substrate
- 2009
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Ingår i: Phys. Stat. Sol. (c) Vol. 6. - : Wiley. ; , s. S772-S775
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Konferensbidrag (refereegranskat)abstract
- Optical spectra of a C-doped (1-101) GaN are investigated via time resolved photoluminescence spectroscopy. Samples with different C-doping levels were prepared by metalorganic vapour phase epitaxy using C2H2 as the doping precursor. A carbon related emission peak is identified at 375 nm which shows typical behaviours for a donor-acceptor-pair emission band. The acceptor level is estimated to be 190 meV which is at 43 meV shallower than that in an Mg doped GaN. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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| 24. |
- Junesand, Carl, et al.
(författare)
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Heteroepitaxial Growth of Indium Phosphide from Nano-openings Made by Masking on a Si(001) Wafer
- 2010
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Ingår i: 2010 22ND INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS (IPRM). - 9781424459209
-
Konferensbidrag (refereegranskat)abstract
- We investigate nano-eptiaxial lateral overgrowth (NELOG) of InP from the nano-sized openings on a seed layer on the silicon wafer, by Hydride Vapor Phase Epitaxy (HVPE). The grown layers were analyzed by cathodoluminescence (CL) in situ a scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results from InP: S growth shows that the boundary plane of the grown layer has a major impact on the luminescence, indicating preferential orientation-dependent doping. Moreover, although there is clear evidence that most of the threading dislocations originating in the InP seed layer/Si interface are blocked by the mask, it appears that new dislocations are generated. Some of these dislocations are bounding planar defects such as stacking faults, possibly generated by unevenness in the mask. Finally, patterns where coalescence takes place at higher thickness seem to result in a rougher surface.
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| 25. |
- Junesand, Carl, et al.
(författare)
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Heteroepitaxial Indium Phosphide on Silicon
- 2010
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Ingår i: SILICON PHOTONICS AND PHOTONIC INTEGRATED CIRCUITS II. - : SPIE. - 9780819481924 ; , s. Q-1-Q-9
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is an intense interest on integration of III-V materials on silicon and silicon-on-insulator for realisation of optical interconnects, optical networking, imaging and disposable photonics for medical applications. Advances in photonic materials, structures and technologies are the main ingredients of this pursuit. We investigate nano epitaxial lateral overgrowth (NELOG) of InP material from the nano openings on a seed layer on the silicon wafer, by hydride vapour phase epitaxy (HVPE). The grown layers were analysed by cathodoluminescence (CL) in situ a scanning electron microscope, time-resolved photoluminescence (TR-PL), and atomic force microscope (AFM). The quality of the layers depends on the growth parameters such as the V/III ratio, growth temperature, and layer thickness. CL measurements reveal that the dislocation density can be as low as 2 - 3.10(7) cm(-2) for a layer thickness of similar to 6 mu m. For comparison, the seed layer had a dislocation density of similar to 1.10(9) cm(-2). Since the dislocation density estimated on theoretical grounds from TRPL measurements is of the same order of magnitude both for NELOG InP on Si and on InP substrate, the dislocation generation appears to be process related or coalescence related. Pertinent issues for improving the quality of the grown InP on silicon are avoiding damage in the openings due to plasma etching, pattern design to facilitate coalescence with minimum defects and choice of mask material compatible with InP to reduce thermal mismatch.
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| 26. |
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| 27. |
- Monemar, Bo, 1942-, et al.
(författare)
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Defects in Gallium Nitride
- 1999
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Ingår i: International Workshop on Materials Science,1999. - Proc. of the International Workshop on Materials Science 99, ed. by F. F. Bekker et al., Vol. 1 : Hanoi National University Publishing House. ; , s. 28-
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Konferensbidrag (refereegranskat)
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| 28. |
- Monemar, Bo, 1942-, et al.
(författare)
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Influence of polarization fields and depletion fields on photoluminescence of AlGaN/GaN multiple quantum well structures
- 2003
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 237:1, s. 353-364
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Tidskriftsartikel (refereegranskat)abstract
- We report on a detailed study of low temperature photoluminescence (PL) in Al0.07Ga0.93N/GaN multiple quantum wells (MQWs). The structures were grown on sapphire with the conventional low temperature AlN nucleation layer and thick GaN buffer layer. Several sets of 5 QW MQW samples were studied, one set with Si doping in the barriers up to or above the metallic limit. Nominally undoped MQW samples were also studied. The spectral behaviour of the doped samples was strongly affected by the near surface depletion field, causing overlap of different spectra from non-equivalent QWs. The QWs closest to the surface are presumably inactive in some samples, due to a very high depletion field. For the case of undoped samples, on the other hand, the near surface QWs are active and most prominent in the PL spectra. The structure from discrete well width variations is here resolved in the PL spectra. The results demonstrate that for structures with no additional capping layer both the depletion field and the polarisation fields need to be considered in the interpretation of experimental data. The theoretically estimated fields in this work are consistent with the experimental spectra. The presence of localisation even in the case of metallic samples, as observed by a constant PL decay time independent of doping, is discussed in terms of penetration of the hole wave functions into the AlGaN barriers. This localisation is also manifested in a sizeable LO phonon coupling strength in all samples studied.
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| 29. |
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| 30. |
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| 31. |
- Monemar, Bo, 1942-, et al.
(författare)
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The 3.466 eV Bound Exciton in GaN
- 2001
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Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 228:2, s. 489-492
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the available optical data for the 3.466 eV bound exciton in GaN, which has been a controversial issue in the recent literature. We conclude that the experimental results are only consistent with the identification as an exciton bound at a neutral acceptor with a spin-like bound hole. The chemical identity is still not clear.
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| 32. |
- Pozina, Galia, 1966-, et al.
(författare)
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Dynamics of bound excitons versus thickness in freestanding GaN wafers grown by halide vapor phase epitaxy
- 2007
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:22
-
Tidskriftsartikel (refereegranskat)abstract
- The bound exciton recombination properties in freestanding GaN layers of various thicknesses grown by halide vapor phase epitaxy have been characterized by time-resolved spectroscopy. Improvement of the donor bound exciton (D0 X) lifetime was observed with increasing GaN layer thickness up to ∼400 μm, while for thicker layers the recombination time of D0 X shows a tendency to saturate. The thickness-dependent behavior of the D0 X decay can be understood in terms of competition between two nonradiative mechanisms: one of which is connected to structural defects, and consequently more important for thinner layers, while for layers with thickness above 400 μm with low structural defect density the recombination time is limited by point defects such as impurities and vacancies. © 2007 American Institute of Physics.
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| 33. |
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| 34. |
- Pozina, Galia, 1966-, et al.
(författare)
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Metastable behavior of the UV luminescence in Mg-doped GaN layers grown on quasibulk GaN templates
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:22
-
Tidskriftsartikel (refereegranskat)abstract
- Metastability of near band gap UV emissions in Mg-doped GaN layers grown by metal-organic vapor phase epitaxy on thick GaN templates grown by halide vapor phase epitaxy has been studied by cathodoluminescence (CL). The CL spectrum changes its initial shape within a few minutes under electron irradiation. The acceptor bound exciton line vanishes while the emissions related to the stacking faults (SFs) of different geometry rise significantly. The increase of the defect-related luminescence is likely caused by recombination enhanced SF formation under electron irradiation. The CL spectrum transformation is permanent at low temperatures, however, the metastable process is reversible if samples are heated to room temperature. © 2007 American Institute of Physics.
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| 35. |
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| 36. |
- Pozina, Galia, 1966-, et al.
(författare)
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Optical properties of metastable shallow acceptors in Mg-doped GaN layers grown by metal-organic vapor phase epitaxy
- 2010
-
Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X. - 9780735407367 ; , s. 110-111
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Konferensbidrag (refereegranskat)abstract
- GaN layers doped by Mg show a metastable behavior of the near-band-gap luminescence caused by electron irradiation or UV excitation. At low temperatures < 30 K the changes in luminescence are permanent. Heating to room temperature recovers the initial low temperature spectrum shape completely. Two acceptors are involved in the recombination process as confirmed by transient PL. In as-grown samples a possible candidate for the metastable acceptor is C-N, while after annealing a second more stable acceptor related to Mg became active.
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| 37. |
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| 38. |
- Rindermann, Jan Junis, et al.
(författare)
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The effect of exciton dimensionality on resonance energytransfer: advances for organic color converters in hybridinorganic/organic LEDs
- 2012
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Ingår i: Proceedings of SPIE. - : SPIE. - 9780819488985 ; , s. 82550I-01-82550I-10
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Konferensbidrag (refereegranskat)abstract
- The dependence of resonance energy transfer from Wannier-Mott excitons to an organic overlayer on excitondimensionality is studied experimentally and by means of supporting simulations. The variation of temperatureeffectively tunes the balance between localized and free excitons, and allows to investigate the effect of theexcitonic potential disorder on resonance energy transfer. Our theoretical calculations give insight into theexperimentally observed temperature dependence of resonance energy transfer, and allow us to quantify thecontribution from localized and free excitons. It is shown that free excitons can undergo resonance energytransfer at a rate that is an order of magnitude higher compared to localized excitons. In planar geometriesnonradiative resonance energy transfer is dominating over radiative energy transfer and hence we propose hybridinorganic-organic LEDs which are optimized for resonance energy transfer to an organic or QD-based colorconverter.
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| 39. |
- Shubina, Tatiana, et al.
(författare)
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Recombination dynamics and lasing in ZnO/ZnMgO single quantum well structures
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:20
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Tidskriftsartikel (refereegranskat)abstract
- We report a time-resolved study of the recombination dynamics in molecular beam epitaxy grown ZnOZnMgO single quantum wells (SQWs) of 1.0-4.5 nm width. The SQWs exhibit different emission properties, depending on both the well width and defect density. Stimulated emission has been achieved at room temperature in a separate confinement double heterostructure having a 3 nm wide SQW as an active region. It has been found that a critical parameter for the lasing is the inhomogeneous broadening of both QW and barrier emission bands. © 2007 American Institute of Physics.
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| 40. |
- Shubina, T.V., et al.
(författare)
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Delay and distortion of light pulses by exciton resonancesin wide-gap semiconductors
- 2012
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Ingår i: Proceedings of the 20th Int. Symp. “Nanostructures: Physics and Technology". - 9785913261793 ; , s. 18-19
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Konferensbidrag (refereegranskat)abstract
- Propagation of light pulses in wide-gap semiconductors, GaN and ZnO, has been studied by time-of-flightspectroscopy. It has been demonstrated that significant light delay exists near an exciton resonance and that this delay isaccompanied by pulse distortion and attenuation. Simulation of the pulse shape in the time-energy plane has permitted us torefine excitonic parameters inherent for bulk materials. The time-of-flight studies done over a wide temperature rangedemonstrate the strong influence of resonant scattering by phonons on the light delay in polar semiconductors.
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| 41. |
- Toropov, A. A., et al.
(författare)
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Magneto-photoluminescence studies of Cd(Mn)Se/Zn(Mn)Se diluted magnetic nanostructures
- 2001
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - 1386-9477 .- 1873-1759. ; 10:1-3, s. 362-367
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Tidskriftsartikel (refereegranskat)abstract
- We report on cw and time-resolved photoluminescence (PL) studies of Cd(Mn)Se/Zn(Mn)Se diluted magnetic semiconductor nanostructures grown by molecular beam epitaxy. Excitonic PL intensity, decay time and Zeeman splitting have been studied systematically as a function of Cd(Mn)Se nominal thickness, Mn concentration and sample design. Wave function mapping has been performed, evidencing the formation of semi-magnetic quantum disk islands in the samples with thick enough Cd(Mn)Se insertions. ⌐ 2001 Elsevier Science B.V.
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| 42. |
- Yu, Hongling, 1987-, et al.
(författare)
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Single-emissive-layer all-perovskite white light-emitting diodes employing segregated mixed halide perovskite crystals
- 2020
-
Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 11:41, s. 11338-11343
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Tidskriftsartikel (refereegranskat)abstract
- Metal halide perovskites have demonstrated impressive properties for achieving efficient monochromatic light-emitting diodes. However, the development of white perovskite light-emitting diodes (PeLEDs) remains a big challenge. Here, we demonstrate a single-emissive-layer all-perovskite white PeLED using a mixed halide perovskite film as the emissive layer. The perovskite film consists of separated mixed halide perovskite phases with blue and red emissions, which are beneficial for suppressing halide anion exchange and preventing charge transfer. As a result, the white PeLED shows balanced white light emission with Commission Internationale de L'Eclairage coordinates of (0.33, 0.33). In addition, we find that the achievement of white light emission from mixed halide perovskites strongly depends on effective modulation of the halide salt precursors, especially lead bromide and benzamidine hydrochloride in our case. Our work provides very useful guidelines for realizing single-emissive-layer all-perovskite white PeLEDs based on mixed halide perovskites, which will spur the development of high-performance white PeLEDs.
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| 43. |
- Zhao, Qingxiang, 1962-, et al.
(författare)
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Surface Recombination in ZnO Nanorods Grown by Aqueous Chemical Method
- 2009
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Ingår i: PHYSICS OF SEMICONDUCTORS. - Melville, N.Y, USA : American Institute of Physics (AIP). - 9780735407367 ; , s. 319-320
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Konferensbidrag (refereegranskat)abstract
- ZnO nanorods on Si substrates were prepared by either a two-steps chemical bath deposition (CBD) method or thermal evaporation technique. 11 was found that the effective decay time of the near bandgap recombinations strongly depends on the method, which was used to grow the ZnO nanorods. ZnO nanorods grown by the CBD exhibit characteriristic two-exponential decay curves, while ZnO nanorods grown by thermal evaporation technique show single exponential decays. The experimental results show that the fast exponential decay from the CBD grown ZnO nanorods is related to the surface recombination, while the slow decay is related to the "bulk" decay. The results also show that an annealing treatment around 500 degrees C to 700 degrees C significantly reduces the surface recombination rate.
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