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- Böttger, Michael, et al.
(författare)
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Electrospraying of colloidal nanoparticles for seeding of nanostructure growth
- 2007
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:10
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Tidskriftsartikel (refereegranskat)abstract
- Nanometre-sized particles (1-100 nm) have unique properties receiving growing attention in wide areas of research. Here, a convenient method to deposit size-selected nanoparticles on surfaces by means of electrospraying colloidal suspensions in the aerosol phase is presented. We demonstrate the deposition of individual nanoparticles and the feasibility of this method in seeding gold particles for nanostructure growth. An advantage of the present method is the easy set-up and operation, using only commercially available machinery and substances. Problems regarding low deposition rates and colloidal remnants are approached, e. g. the aerosol flow is examined in a differential mobility analyser. This method is not material dependent and could be extended to deposit any colloidal particle.
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| 2. |
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| 3. |
- Johansson, Jonas, et al.
(författare)
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The structure of <1 1 1 > B oriented GaP nanowires
- 2007
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 298, s. 635-639
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Tidskriftsartikel (refereegranskat)abstract
- Nanowires of zinc blende crystal structure, grown in the < 111 > B direction usually have a large number of twin plane defects. In order to investigate this phenomenon, we grow GaP nanowires with metal-organic vapor phase epitaxy. By rotating the nanowires in a high resolution transmission electron microscope, we show that the nanowire segments between the twin planes are of octahedral shape and are terminated by {111} facets. Due to the alternating orientations of these twin octahedra, the sidewalls of the nanowires can be described as microfaceted surfaces with an overall orientation of 11 1 2}, but composed of alternating 11 1 I}A and {1 I 1}B facets. Moreover, the segment thicknesses follow exponential distributions, which show that there is a certain probability of twin plane formation, which is independent of segment thickness. (c) 2006 Elsevier B.V. All rights reserved.
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| 6. |
- Wacaser, Brent
(författare)
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Nanoscale Crystal Growth: The Importance of Interfaces and Phase Boundaries Kristallväxt på Nanometer Skala: Vikten av Ytor och Gränser
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surfaces and interfaces have a special significance to nanotechnology because the surface/volume ratio of nanomaterials is larger than for bulk materials. Therefore, interfaces of nanomaterials are usually more important to the properties of nanomaterials than for larger scale materials. Furthermore, crystal growth occurs at the interfaces between the growing crystals and the supply media. An understanding of the interfaces is therefore essential to understanding growth. Nanoscale crystal growth of three, two, and to some extent one-dimensional crystals has been explained in the context of crystalline interfaces. This understanding has helped improve production of nanostructures and devices that are both scientifically and commercially beneficial. This dissertation expands on the importance of interfaces and atomistic processes occurring at these interfaces; explaining the growth and control of different nanocrystals. A brief review of crystal growth terminology and theory is given. A new technology recently developed to produce compound semiconductor quantum dots is described within the context of the interfaces involved. The majority of the dissertation will focus on explaining and understanding growth of one-dimensional nanostructures, called nanowires, grown in a three-phase system. The currently accepted growth mechanism for nanowires of this type is the vapor-liquid-solid (VLS) mechanism. The VLS and similar mechanisms lack details about the atomistic processes involved in wire growth. When these atomistic processes are examined, it is revealed that there are several different names describing what are proposed to be ?different? mechanisms that in reality rely on the same atomistic processes. The key to understanding nanowire growth lies in understanding the atomistic processes occurring at the interfaces. Due to the fundamental similarities in the mechanisms with different names, the name ?Preferential Phase-Boundary Nucleation? (PPBN) is suggested as a replacement for the many different names. Unlike previous names this name is relevant to the processes as well as emphasizing the importance of the phases and the interfaces. A better understanding of interfaces and the processes that occur at them leads to a greater understanding and control of the growth of crystalline nanostructures.
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| 7. |
- Wacaser, Brent, et al.
(författare)
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Size-selected compound semiconductor quantum dots by nanoparticle conversion
- 2007
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a novel technology, called nanoparticle conversion, for producing compound semiconductor quantum dots (QDs) in which the dot size, surface density, position, and the materials system are all independently controlled. Nanoparticle conversion also lends itself to spatially controlled positioning of QDs. To demonstrate this technology we report the formation of InP QDs using nanoparticle conversion. We have produced QDs on substrates of different types by converting randomly and lithographically positioned nanoparticles into compound semiconductors in a chemical vapour deposition system. Electron microscopy and atomic force microscopy measurements reveal that the morphology of these QDs is similar to that of QDs produced by other techniques. Photo- and cathodoluminescence measurements show that the converted nanoparticles exhibit properties and behaviours typical of semiconductor QDs. These include quantum confinement, free-to-bound recombination and blinking. Production of multi-component QDs like InP, GaN, and InAsP on various substrates like Si, SiO2, and sapphire show that this technology can produce a wide variety of different types of QD on different substrates with minimal need for process optimization.
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| 8. |
- Zanolli, Zeila, et al.
(författare)
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Core-shell InP-CdS nanowires: fabrication and study
- 2007
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 19:29
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Tidskriftsartikel (refereegranskat)abstract
- InP nanowires are fabricated by organo-metallic vapour phase epitaxy and studied via photoluminescence measurements performed on single nanowires, finding evidence of state filling with increasing excitation power density. To increase flexibility in fabrication technology we developed a wet chemical procedure to grow a CdS shell on these wires. In these InP-CdS wires the luminescence efficiency was decreased with respect to the bare wires. The CdS capping procedure needs further investigations to improve the emission properties of nanowires, in order to become technically useful. We suggest as possible improvements of this technique to increase the bath temperature and/or illuminate the sample with UV radiation during the capping procedure.
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