| 1. |
- Dick Thelander, Kimberly, et al.
(författare)
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Control of III-V nanowire crystal structure by growth parameter tuning
- 2010
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 25:2
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Tidskriftsartikel (refereegranskat)abstract
- In this work we investigate the variation of the crystal structure of gold-seeded III-V nanowires with growth parameters, in order to gain a cohesive understanding of these effects. We investigate six III-V materials: GaAs, InAs, GaP, InP, GaSb and InSb, over a variation of growth conditions. All six of these materials exhibit a cubic zinc blende structure in bulk, but twin planes and stacking faults, as well as a hexagonal wurtzite structure, are commonly observed in nanowires. Parameters which may affect the crystal structure include growth temperature and pressure, precursor molar fraction and V/III ratio, nanowire diameter and surface density, and impurity atoms. We will focus on temperature, precursor molar fraction and V/III ratio. Our observations are compared to previous reports in the literature of the III-V nanowire crystal structure, and interpreted in terms of existing models. We propose that changes in the crystal structure with growth parameters are directly related to changes in the stable side facets.
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| 2. |
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| 3. |
- Happonen, Matti, et al.
(författare)
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The comparison of particle oxidation and surface structure of diesel soot particles between fossil fuel and novel renewable diesel fuel
- 2010
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Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 89:12, s. 4008-4013
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Tidskriftsartikel (refereegranskat)abstract
- Conventional fossil diesel fuel and renewable diesel fuel based on hydrotreated vegetable oils (HVO) were compared regarding the oxidation characteristics of the generated soot particulate. The comparison was performed by utilizing a high-temperature oxidation tandem differential mobility analyser in which monodisperse soot aerosol was first selected and then heated in a high-temperature furnace. The particle size reduction caused by oxidation during the furnace treatment was then measured as a function of furnace temperature. The results indicate that soot oxidation is very similar between the studied fuels. This is supported by the obtained HR-TEM images and EELS-spectra which were practically indistinguishable between different fuels and engine conditions. The similar oxidation properties and surface structure between fossil and HVO-based diesel fuels imply that the oxidative aftertreatment devices designed for fossil diesel should work well also with the studied renewable diesel fuel. (C) 2010 Elsevier Ltd. All rights reserved.
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| 4. |
- Hillerich, Karla, et al.
(författare)
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Epitaxial InP nanowire growth from Cu seed particles
- 2011
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 315:1, s. 134-137
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Konferensbidrag (refereegranskat)abstract
- Cu-seeded epitaxial growth of vertically aligned InP nanowires is reported for the first time. The nanowires were grown at temperatures between 290 and 420 degrees C by metal-organic vapor phase epitaxy (MOVPE) from particles formed from Cu thin films. In the temperature range of 340-370 degrees C high yields of vertically aligned nanowires could be achieved. The nanowire crystal structure and the particle composition were investigated by TEM and XEDS. The nanowires showed a zinc blende structure and a post-growth particle composition of 64 at% Cu and 36 at% In. (C) 2010 Elsevier B.V. All rights reserved.
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| 5. |
- Jönsson, Linnéa, et al.
(författare)
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The effect of electrode composition on bimetallic AgAu nanoparticles produced by spark ablation
- 2024
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 177
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Tidskriftsartikel (refereegranskat)abstract
- A flexible way to generate bimetallic nanoparticles with high control of their composition is to use spark ablation of alloyed electrodes. It has been generally accepted and stated that particles produced using spark ablation of alloyed electrodes obtain the same chemical composition as the electrodes. However, we identify a lack of studies fully supporting the connection between electrode and particle composition, presented in a small literature survey. The aim of the study is, hence, to explore the validity of the statement by analysing the relation between alloyed electrodes and their resulting particle composition using three sets of AgAu electrodes containing Au and 25, 50, and 75 atomic % Ag, respectively. The resulting composition is thoroughly investigated using both single particle (scanning- and transmission electron microscopy) and ensemble particle techniques (inductive coupled plasma-mass spectroscopy, x-ray photoelectron spectroscopy, x-ray fluorescence, and optical measurements of surface plasmon resonance. We also investigate how sample size (e.g., the number of particles analysed) affects the reliability of the resulting sample mean. For single-particle measurements of a sample with a compositional standard deviation of a few atomic percentage points, a sample size of 20 particles is a good benchmark for obtaining reliable results of the sample mean. Furthermore, this article aims to challenge the practice in which the composition of nanoparticles is measured, presented, and interpreted, to improve and facilitate future research related to this topic. From the results of this study, it could be concluded that for the investigated Ag–Au material system, the particles obtained a composition very similar to the alloyed AgAu electrodes.
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| 6. |
- Karki, Khadga Jung, et al.
(författare)
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Multiple exciton generation in nano-crystals revisited: Consistent calculation of the yield based on pump-probe spectroscopy.
- 2013
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Multiple exciton generation (MEG) is a process in which more than one exciton is generated upon the absorption of a high energy photon, typically higher than two times the band gap, in semiconductor nanocrystals. It can be observed experimentally using time resolved spectroscopy such as the transient absorption measurements. Quantification of the MEG yield is usually done by assuming that the bi-exciton signal is twice the signal from a single exciton. Herein we show that this assumption is not always justified and may lead to significant errors in the estimated MEG yields. We develop a methodology to determine proper scaling factors to the signals from the transient absorption experiments. Using the methodology we find modest MEG yields in lead chalcogenide nanocrystals including the nanorods.
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| 7. |
- Mandl, Bernhard, et al.
(författare)
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Self-Seeded Axio-Radial InAs-InAs1-xPx Nanowire Heterostructures beyond "common" VLS Growth
- 2018
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 18:1, s. 144-151
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Tidskriftsartikel (refereegranskat)abstract
- Semiconductors are essential for modern electronic and optoelectronic devices. To further advance the functionality of such devices, the ability to fabricate increasingly complex semiconductor nanostructures is of utmost importance. Nanowires offer excellent opportunities for new device concepts; heterostructures have been grown in either the radial or axial direction of the core nanowire but never along both directions at the same time. This is a consequence of the common use of a foreign metal seed particle with fixed size for nanowire heterostructure growth. In this work, we present for the first time a growth method to control heterostructure growth in both the axial and the radial directions simultaneously while maintaining an untapered self-seeded growth. This is demonstrated for the InAs/InAs1-xPx material system. We show how the dimensions and composition of such axio-radial nanowire heterostructures can be designed including the formation of a "pseudo-superlattice" consisting of five separate InAs1-xPx segments with varying length. The growth of axio-radial nanowire heterostructures offers an exciting platform for novel nanowire structures applicable for fundamental studies as well as nanowire devices. The growth concept for axio-radial nanowire heterostructures is expected to be fully compatible with Si substrates.
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| 8. |
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| 9. |
- Messing, Maria, et al.
(författare)
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Generation of size-selected gold nanoparticles by spark discharge - for growth of epitaxial nanowires
- 2009
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Ingår i: Gold Bulletin. - 0017-1557. ; 42:1, s. 20-26
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Tidskriftsartikel (refereegranskat)abstract
- One-dimensional semiconductor nanowires are a promising candidate for future electronic devices. The epitaxial growth of nanowires is often mediated by metal seed particles, usually gold particles. In this paper the setup of a simple and robust technique to generate nanometer-sized aerosol gold particles by spark discharge is described. Furthermore we demonstrate for the first time that particles generated by spark discharge can be used to design advanced nanoelectronic structures, namely nanowires. In order to obtain compact, spherical particles suitable for nanowire growth, the spark-generated agglomerate particles were reshaped in a special compaction furnace. The reshaped particles were used to seed the growth of epitaxial GaP and InP nanowires, by metal organic vapor phase epitaxy, which was shown to be a reliable and reproducible method. This work indicates the possibility of using spark-discharge generated gold particles for the creation of new electronic devices even at large scale processing.
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| 10. |
- Messing, Maria, et al.
(författare)
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Growth of Straight InAs-on-GaAs Nanowire Heterostructures.
- 2011
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:9, s. 3899-3905
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Tidskriftsartikel (refereegranskat)abstract
- One of the main motivations for the great interest in semiconductor nanowires is the possibility of easily growing advanced heterostructures that might be difficult or even impossible to achieve in thin films. For III-V semiconductor nanowires, axial heterostructures with an interchange of the group III element typically grow straight in only one interface direction. In the case of InAs-GaAs heterostructures, straight nanowire growth has been demonstrated for growth of GaAs on top of InAs, but so far never in the other direction. In this article, we demonstrate the growth of straight axial heterostructures of InAs on top of GaAs. The heterostructure interface is sharp and we observe a dependence on growth parameters closely related to crystal structure as well as a diameter dependence on straight nanowire growth. The results are discussed by means of accurate first principles calculations of the interfacial energies. In addition, the role of the gold seed particle, the effect of its composition at different stages during growth, and its size are discussed in relation to the results observed.
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