| 1. |
- Borg, Mattias, et al.
(författare)
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GaAs/GaSb nanowire heterostructures grown by MOVPE
- 2008
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 310:18, s. 4115-4121
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Tidskriftsartikel (refereegranskat)abstract
- We report Au-assisted growth of GaAs/GaSb nanowire heterostructures on GaAs(1 1 1)B-substrates by metal-organic vapor phase epitaxy. The growth is studied at various precursor molar fractions and temperatures, in order to optimize the growth conditions for the GaSb nanowire segment. In contrast to most other III-V nanowire systems, the GaSb nanowire growth is Group V-limited under most conditions. We found that depending on the TMSb molar fraction, the seed particle is either supersaturated AuGa or AuGa2 during GaSb growth. The high Ga content in the particle gives a characteristic diameter increase between the GaAs and GaSb segment. From TEM and XEDS measurements we conclude that the GaSb nanowire growth occurs along either the AuGa-GaSb or AuGa2-GaSb pseudo-binaries of the Au-Ga-Sb ternary phase diagram. Finally, the GaSb nanowires exhibit untapered radial growth on the {1 (1) over bar 0} side facets. (C) 2008 Elsevier B.V. All rights reserved.
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| 2. |
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| 3. |
- Ganjipour, Bahram, et al.
(författare)
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Electrical properties of GaSb/InAsSb core/shell nanowires
- 2014
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 25:42
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Tidskriftsartikel (refereegranskat)abstract
- Temperature dependent electronic properties of GaSb/InAsSb core/shell and GaSb nanowires have been studied. Results from two-probe and four-probe measurements are compared to distinguish between extrinsic (contact-related) and intrinsic (nanowire) properties. It is found that a thin (2-3 nm) InAsSb shell allows low barrier charge carrier injection to the GaSb core, and that the presence of the shell also improves intrinsic nanowire mobility and conductance in comparison to bare GaSb nanowires. Maximum intrinsic field effect mobilities of 200 and 42 cm(2) Vs(-1) were extracted for the GaSb/InAsSb core/shell and bare-GaSb NWs at room temperature, respectively. The temperature-dependence of the mobility suggests that ionized impurity scattering is the dominant scattering mechanism in bare GaSb while phonon scattering dominates in core/shell nanowires. Top-gated field effect transistors were fabricated based on radial GaSb/InAsSb heterostructure nanowires with shell thicknesses in the range 5-7 nm. The fabricated devices exhibited ambipolar conduction, where the output current was studied as a function of AC gate voltage and frequency. Frequency doubling was experimentally demonstrated up to 20 kHz. The maximum operating frequency was limited by parasitic capacitance associated with the measurement chip geometry.
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| 4. |
- Mårtensson, Thomas, et al.
(författare)
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Nanowire arrays - a toolbox for the future
- 2004
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Ingår i: Book of extended abstracts: 8th Intl Conf Nanoscale Sci Technol, Venice, Italy (2004).
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Konferensbidrag (refereegranskat)
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| 5. |
- Anttu, Nicklas, et al.
(författare)
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Crystal Phase-Dependent Nanophotonic Resonances in InAs Nanowire Arrays
- 2014
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 14:10, s. 5650-5655
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructures have many material, electronic, and optical properties that are not found in bulk systems and that are relevant for technological applications. For example, nanowires realized from III-V semiconductors can be grown into wurtzite crystal structure. This crystal structure does not naturally exist in bulk where these materials form the zinc-blende counterpart. Being able to concomitantly grow these nanowires in the zinc-blende and/or wurtzite crystal structure prlovides an important degree of control for the design and optimization of optoelectronic applications based on these semiconductor nanostructures. However, the refractive indices of this new crystallographic phase have so far not been elucidated. This shortcoming makes it impossible to predict and utilize he full potential of these new nanostructured materials for optoelectronics applications a careful design and optimization of optical resonances by tuning the nanostrucuted geometry is needed to achieve optimal performance. Here, we report and analyze striking differeences in the optical response of nanophotonic resonances in wurtzite and zinc-blend InAs nanowire arrays. Specifically, through reflectance measurements we find that the resonance can be tuned down to lambda approximate to 380 nm in wurtzite nanowires by decreasing the nanowire diameter. In stark contrast, a similar tuning to below approximate to 500 nm is not possible in the zinc-blende nanowires. Furthermore, we find that the wurtzite nanowires can absorb twice as strongly as the zinc-blende nanowires. We attribute these strikingly large differences in resonant behavior to large differences between the refractive indices of the two crystallographic phases realized in these nanostructures. We anticipate our finding to be relevant for other III-B materials as well as for all material systems that manifest polytypism. Taken together, our results demonstrate crystal phase engineering as a potentially new design dimension for optoelectronics applications.
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| 6. |
- Borgström, Magnus, et al.
(författare)
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Precursor evaluation for in situ InP nanowire doping
- 2008
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:44
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Tidskriftsartikel (refereegranskat)abstract
- The use of tetraethyltin (TESn) and dimethylzinc (DMZn) as in situ n- and p-dopant precursors during particle-assisted growth of InP nanowires is reported. Gate voltage dependent transport measurements demonstrate that the nanowires can be predictably synthesized as either n- or p-type. These doped nanowires can be characterized based on their electric field response and we find that n- type doping scales over a range from 10(17) to 10(19) cm(-3) with increasing input TESn dopant molar fraction. On the other hand, the p-type doping using DMZn saturates at low levels, probably related to a strong increase in nanowire growth rate with increasing DMZn molar fractions. By optimizing growth conditions with respect to tapering, axial pn-junctions exhibiting rectifying behavior were fabricated. The pn-junctions can be operated as light emitting diodes.
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| 7. |
- Caroff, Philippe, et al.
(författare)
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Controlled polytypic and twin-plane superlattices in iii-v nanowires.
- 2009
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3395 .- 1748-3387. ; 4:1, s. 50-55
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Tidskriftsartikel (refereegranskat)abstract
- Semiconductor nanowires show promise for use in nanoelectronics, fundamental electron transport studies, quantum optics and biological sensing. Such applications require a high degree of nanowire growth control, right down to the atomic level. However, many binary semiconductor nanowires exhibit a high density of randomly distributed twin defects and stacking faults, which results in an uncontrolled, or polytypic, crystal structure. Here, we demonstrate full control of the crystal structure of InAs nanowires by varying nanowire diameter and growth temperature. By selectively tuning the crystal structure, we fabricate highly reproducible polytypic and twin-plane superlattices within single nanowires. In addition to reducing defect densities, this level of control could lead to bandgap engineering and novel electronic behaviour.
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| 8. |
- Chen, Jianing, et al.
(författare)
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Surface-enhanced Raman scattering of rhodamine 6G on nanowire arrays decorated with gold nanoparticles
- 2008
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:27, s. 5-275712
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the surface-enhanced Raman scattering (SERS) of rhodamine 6G (R6G) adsorbed on Au nanoparticles attached to InP nanowires. We find that nanowire arrays act as frameworks for effective SERS substrates with a significantly higher Raman signal sensitivity than a planar framework of Au nanoparticles adsorbed two-dimensionally on a flat surface. The SERS signal displays a clear polarization-dependent effect when the nanowires are arranged in a row. We also find that the SERS signal increases with time during continuous laser illumination. The plasmon-enhanced optical forces between Au nanoparticles may either move pairs of nanoparticles closer together or attract adsorbed molecules by moving them to the junctions of Au nanoparticle aggregates. Such effects by plasmon optical forces may cause the observed increase of the SERS signal with continuous laser illumination.
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| 9. |
- Chen, Jianing, et al.
(författare)
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Tip-enhanced Raman scattering of p-thiocresol molecules on individual gold nanoparticles
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:9
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of tip-enhanced Raman scattering on Au aerosol nanoparticles deposited on gold films. Under the tunneling current state, the Au tip and the Au aerosol nanoparticle form a narrow cavity, where large electromagnetic field enhancements are created to enhance Raman scattering enormously. Colorless p-thiocresol molecules are used as probe molecules. The estimated Raman enhancement is about nine orders of magnitude for the tip/particle configuration.
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| 10. |
- Deppert, Knut, et al.
(författare)
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Epitaxielle Kristallnadeln und -bäume
- 2005
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Ingår i: Book of abstracts: DGKK-Jahrestagung, Köln, Germany (2005).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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