| 1. |
- 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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| 2. |
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| 3. |
- Ek, Martin, et al.
(författare)
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Compositional analysis of oxide-embedded III-V nanostructures
- 2022
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 33:37
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Tidskriftsartikel (refereegranskat)abstract
- Nanowire growth enables creation of embedded heterostructures, where one material is completely surrounded by another. Through materials-selective post-growth oxidation it is also possible to combine amorphous oxides and crystalline, e.g. III-V materials. Such oxide-embedded structures pose a challenge for compositional characterization through transmission electron microscopy since the materials will overlap in projection. Furthermore, materials electrically isolated by an embedding oxide are more sensitive to electron beam-induced alterations. Methods that can directly isolate the embedded material, preferably at reduced electron doses, will be required in this situation. Here, we analyse the performance of two such techniques-local lattice parameter measurements from high resolution micrographs and bulk plasmon energy measurements from electron energy loss spectra-by applying them to analyse InP-AlInP segments embedded in amorphous aluminium oxide. We demonstrate the complementarity of the two methods, which show an overall excellent agreement. However, in regions with residual strain, which we analyse through molecular dynamics simulations, the two techniques diverge from the true value in opposite directions.
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| 4. |
- Lehmann, Sebastian, et al.
(författare)
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Simultaneous Growth of Pure Wurtzite and Zinc Blende Nanowires
- 2019
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 19:4, s. 2723-2730
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Tidskriftsartikel (refereegranskat)abstract
- The opportunity to engineer III-V nanowires in wurtzite and zinc blende crystal structure allows for exploring properties not conventionally available in the bulk form as well as opening the opportunity for use of additional degrees of freedom in device fabrication. However, the fundamental understanding of the nature of polytypism in III-V nanowire growth is still lacking key ingredients to be able to connect the results of modeling and experiments. Here we show InP nanowires of both pure wurtzite and pure zinc blende grown simultaneously on the same InP [100]-oriented substrate. We find wurtzite nanowires to grow along «111»B and zinc blende counterparts along «111»A. Further, we discuss the nucleation, growth, and polytypism of our nanowires against the background of existing theory. Our results demonstrate, first, that the crystal growth conditions for wurtzite and zinc blende nanowire growth are not mutually exclusive and, second, that the interface energies predominantly determine the crystal structure of the nanowires.
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| 5. |
- Wallentin, Jesper, et al.
(författare)
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Changes in Contact Angle of Seed Particle Correlated with Increased Zincblende Formation in Doped InP Nanowires.
- 2010
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:12, s. 4807-4812
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Tidskriftsartikel (refereegranskat)abstract
- Nanowires grown with the vapor-liquid-solid method commonly exhibit polytypism, showing both zincblende and wurtzite crystal structure. We have grown p-type InP nanowires using DEZn as a dopant precursor and studied the wetting of the seed particle and the nanowire crystal structure. The nanowires grown with high DEZn molar fractions exhibit deformed seed particles after growth. We observe 20% smaller nanowire diameter at the highest DEZn molar fraction, indicating a significant increase in contact angle of the seed particle during growth. The decrease in diameter correlates with an increase in zincblende segment length as measured by TEM. We explain the results with a modified nucleation model.
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| 6. |
- Wallentin, Jesper, et al.
(författare)
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Degenerate p-doping of InP nanowires for large area tunnel diodes
- 2011
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 99:25
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated p-doping of InP nanowires using diethyl zinc. Two-terminal devices showed non-linear source-drain characteristics and p-type gate dependence. Electron beam induced current measurements were employed to determine minority carrier diffusion lengths. We used large-area tunnel diodes to demonstrate degenerate doping, showing peak current densities of up to 0.11 A/cm(2) and room temperature peak to valley current ratios of 5.3. These results demonstrate that high p- and n-doping, paired with sharp doping profiles, can be achieved in InP nanowires. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3669697]
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| 7. |
- Wallentin, Jesper, et al.
(författare)
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Electron Trapping in InP Nanowire FETs with Stacking Faults.
- 2012
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 12:1, s. 151-155
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Tidskriftsartikel (refereegranskat)abstract
- Semiconductor III-V nanowires are promising components of future electronic and optoelectronic devices, but they typically show a mixed wurtzite-zinc blende crystal structure. Here we show, theoretically and experimentally, that the crystal structure dominates the conductivity in such InP nanowires. Undoped devices show very low conductivities and mobilities. The zincblende segments are quantum wells orthogonal to the current path and our calculations indicate that an electron concentration of up to 4.6 × 10(18) cm(-3) can be trapped in these. The calculations also show that the room temperature conductivity is controlled by the longest zincblende segment, and that stochastic variations in this length lead to an order of magnitude variation in conductivity. The mobility shows an unexpected decrease for low doping levels, as well as an unusual temperature dependence that bear resemblance with polycrystalline semiconductors.
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| 8. |
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| 9. |
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| 10. |
- Wallentin, Jesper, et al.
(författare)
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Probing the Wurtzite Conduction Band Structure Using State Filling in Highly Doped InP Nanowires.
- 2011
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:Online May 23, 2011, s. 2286-2290
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Tidskriftsartikel (refereegranskat)abstract
- We have grown InP nanowires doped with hydrogen sulfide, which exhibit sulfur concentrations of up to 1.4%. The highest doped nanowires show a pure wurtzite crystal structure, in contrast to bulk InP which has the zinc blende structure. The nanowires display photoluminescence which is strongly blue shifted compared with the band gap, well into the visible range. We find evidence of a second conduction band minimum at the gamma point about 0.23 eV above the band edge, in excellent agreement with recent theoretical predictions. Electrical measurements show high conductivity and breakdown currents of 10(7) A/cm(2).
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