| 1. |
- Bi, Zhaoxia, et al.
(författare)
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InN quantum dots on GaN nanowires grown by MOVPE
- 2014
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Ingår i: physica status solidi (c). - : Wiley. - 1862-6351 .- 1610-1642 .- 1610-1634. ; 11, s. 421-424
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Tidskriftsartikel (refereegranskat)abstract
- In this work, growth of InN quantum dots (QDs) on GaN nanowires (NWs) by metal-organic vapour phase epitaxy is demonstrated, illustrating the feasibility to combine 0D and 1D structures for nitride semiconductors. Selective area growth was used to generate arrays of c-oriented GaN NWs using Si3N4 as the mask material. In general, InN QDs tend to form at the NW edges between the m-plane side facets, but the QD growth can also be tuned to the side facets by controlling the growth temperature and the growth rate. TEM characterization reveals that I1-type stacking faults are formed in the QDs and originate from the misfit dislocations at the InN/GaN interface. Photoluminescence measurement at 4 K shows that the peak shifts to high energy with reduced dot size. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 2. |
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| 3. |
- Bi, Zhaoxia, et al.
(författare)
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Self-assembled InN quantum dots on side facets of GaN nanowires
- 2018
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 123:16
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembled, atomic diffusion controlled growth of InN quantum dots was realized on the side facets of dislocation-free and c-oriented GaN nanowires having a hexagonal cross-section. The nanowires were synthesized by selective area metal organic vapor phase epitaxy. A 3 Å thick InN wetting layer was observed after growth, on top of which the InN quantum dots formed, indicating self-assembly in the Stranski-Krastanow growth mode. We found that the InN quantum dots can be tuned to nucleate either preferentially at the edges between GaN nanowire side facets, or directly on the side facets by tuning the adatom migration by controlling the precursor supersaturation and growth temperature. Structural characterization by transmission electron microscopy and reciprocal space mapping show that the InN quantum dots are close to be fully relaxed (residual strain below 1%) and that the c-planes of the InN quantum dots are tilted with respect to the GaN core. The strain relaxes mainly by the formation of misfit dislocations, observed with a periodicity of 3.2 nm at the InN and GaN hetero-interface. The misfit dislocations introduce I1 type stacking faults (...ABABCBC...) in the InN quantum dots. Photoluminescence investigations of the InN quantum dots show that the emissions shift to higher energy with reduced quantum dot size, which we attribute to increased quantum confinement.
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| 4. |
- Bolinsson, Jessica, et al.
(författare)
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GaAs/AlGaAs heterostructure nanowires studied by cathodoluminescence
- 2014
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Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 7:4, s. 473-490
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Tidskriftsartikel (refereegranskat)abstract
- In this report we explore the structural and optical properties of GaAs/AlGaAs heterostructure nanowires grown by metalorganic vapour phase epitaxy using gold seed-particles. The optical studies were done by low-temperature cathodoluminescence (CL) in a scanning electron microscope (SEM). We perform a systematic investigation of how the nanowire growth-temperature affects the total photon emission, and variations in the emission energy and intensity along the length of the nanowires. The morphology and crystal structures of the nanowires were investigated using SEM and transmission electron microscopy (TEM). In order to correlate specific photon emission characteristics with variations in the nanowire crystal structure directly, TEM and spatially resolved CL measurements were performed on the same individual nanowires. We found that the main emission energy was located at around 1.48 eV, and that the emission intensity was greatly enhanced when increasing the GaAs nanowire core growth temperature. The data strongly suggests that this emission energy is related to rotational twins in the GaAs nanowire core. Our measurements also show that radial overgrowth by GaAs on the GaAs nanowire core can have a deteriorating effect on the optical quality of the nanowires. Finally, we conclude that an in situ pre-growth annealing step at a sufficiently high temperature significantly improves the optical quality of the nanowires.
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| 5. |
- Borgström, Magnus, et al.
(författare)
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In Situ Etching for Total Control Over Axial and Radial Nanowire Growth
- 2010
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Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 3:4, s. 264-270
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Tidskriftsartikel (refereegranskat)abstract
- We report a method using in situ etching to decouple the axial from the radial nanowire growth pathway, independent of other growth parameters. Thereby a wide range of growth parameters can be explored to improve the nanowire properties without concern of tapering or excess structural defects formed during radial growth. We demonstrate the method using etching by HCl during InP nanowire growth. The improved crystal quality of etched nanowires is indicated by strongly enhanced photoluminescence as compared to reference nanowires obtained without etching.
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| 6. |
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| 7. |
- Gustafsson, Anders, et al.
(författare)
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GaAs-based Nanowires Studied by Low-Temperature Cathodoluminescence
- 2011
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596 .- 1742-6588. ; 326, s. 012042-012042
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Konferensbidrag (refereegranskat)abstract
- We present cathodoluminescence data of nanowires (NWs) grown using size-selected gold particles as seeds. The NWs have a GaAs core with a diameter of 50 nm and a length of several mu m. The NWs in this study were generally covered with a shell of AlGaAs. With increasing growth temperature, the emission intensity increases significantly. From a variety of growth conditions, we conclude that the exposed sides of the NWs during growth play an important role in the emission intensity. The diffusion of carriers was studied by inserting a segment of GaInAs in GaAs NWs. By capping the NWs with an AlGaAs shell, we observe a tenfold increase in the diffusion length along the core.
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| 8. |
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| 9. |
- Heurlin, Magnus, et al.
(författare)
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Continuous gas-phase synthesis of nanowires with tunable properties.
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 492:7427, s. 90-94
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Tidskriftsartikel (refereegranskat)abstract
- Semiconductor nanowires are key building blocks for the next generation of light-emitting diodes, solar cells and batteries. To fabricate functional nanowire-based devices on an industrial scale requires an efficient methodology that enables the mass production of nanowires with perfect crystallinity, reproducible and controlled dimensions and material composition, and low cost. So far there have been no reports of reliable methods that can satisfy all of these requirements. Here we show how aerotaxy, an aerosol-based growth method, can be used to grow nanowires continuously with controlled nanoscale dimensions, a high degree of crystallinity and at a remarkable growth rate. In our aerotaxy approach, catalytic size-selected Au aerosol particles induce nucleation and growth of GaAs nanowires with a growth rate of about 1 micrometre per second, which is 20 to 1,000 times higher than previously reported for traditional, substrate-based growth of nanowires made of group III-V materials. We demonstrate that the method allows sensitive and reproducible control of the nanowire dimensions and shape--and, thus, controlled optical and electronic properties--through the variation of growth temperature, time and Au particle size. Photoluminescence measurements reveal that even as-grown nanowires have good optical properties and excellent spectral uniformity. Detailed transmission electron microscopy investigations show that our aerotaxy-grown nanowires form along one of the four equivalent〈111〉B crystallographic directions in the zincblende unit cell, which is also the preferred growth direction for III-V nanowires seeded by Au particles on a single-crystal substrate. The reported continuous and potentially high-throughput method can be expected substantially to reduce the cost of producing high-quality nanowires and may enable the low-cost fabrication of nanowire-based devices on an industrial scale.
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| 10. |
- Kawaguchi, Kenichi, et al.
(författare)
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InAs quantum dots and quantum wells grown on stacking-fault controlled InP nanowires with wurtzite crystal structure
- 2011
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 99:13
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Tidskriftsartikel (refereegranskat)abstract
- Heteroepitaxial growth of InAs was investigated on sidewalls of InP nanowires (NWs) using metal-organic vapor phase epitaxy. InAs quantum wells (QWs) with smooth surface were formed on the InP NWs having perfect wurtzite phase structure. On the other hand, InAs quantum dots (QDs) were formed on wurtzite InP NWs purposely introduced with stacking-fault segments. Photoluminescence from single NWs attributed to both QWs and QDs was observed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3646386]
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