| 1. |
- Berg, Alexander, et al.
(författare)
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Growth and characterization of wurtzite GaP nanowires with control over axial and radial growth by use of HCl in-situ etching
- 2014
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 386, s. 47-51
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis of non-tapered wurtzite (WZ) GaP nanowires by use of in-situ etching and the structural and optical characterization thereof. HCl was evaluated as an in-situ etchant in order to impede the onset of radial growth since the WZ crystal phase in GaP nanowires preferentially grows at relatively high growth temperatures around 600 degrees C, at which strong radial growth typically occurs. Transmission electron microscopy measurements confirmed non-tapered WZ GaP nanowires after growth. Photoluminescence characterization revealed defect related red emission, possibly related to transitions within the bandgap. Raman measurements show that the phonon energies in WZ GaP are very close in energy to the phonon energies in zinc blende GaP. (C) 2013 Elsevier B.V. All rights reserved.
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| 2. |
- Bolinsson, Jessica, et al.
(författare)
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Diffusion length measurements in axial and radial heterostructured nanowires using cathodoluminescence
- 2011
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 315:1, s. 138-142
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Konferensbidrag (refereegranskat)abstract
- We have measured the ambipolar diffusion lengths in nanowires with GaAs and AlGaAs core material using cathodoluminescence imaging. This was done by combining III-V semiconductor materials with different bandgaps in single nanowires. We show that it is possible to record intensity profiles of the emission from segments of lower bandgap material positioned along the nanowire length and in this way gain an insight on important carrier transport properties of the nanowire core material. We present diffusion data for GaAs and AlGaAs nanowire core material in different radially and axially heterostructured nanowires and show that the diffusion of carriers is greatly increased by capping the nanowires with a higher-bandgap material. In addition, we show how a decoupling of the radial and axial growth during particle-seeded growth is necessary in order to reach long diffusion lengths along the core of axially heterostructured nanowires. In addition, for ternary compounds (InGaAs and AlGaAs), we observe compositional differences for radial and axial nanowire growth. (C) 2010 Elsevier B.V. All rights reserved.
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| 3. |
- Borg, Mattias, et al.
(författare)
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Geometric model for metalorganic vapour phase epitaxy of dense nanowire arrays
- 2013
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 366, s. 15-19
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Tidskriftsartikel (refereegranskat)abstract
- We propose a geometric model to estimate the contribution of substrate surface diffusion to growth of dense nanowire arrays using metalorganic vapour phase epitaxy. It is shown that the nanowire mantle area becomes the most significant collector of growth material when the nanowire diameter is large and the inter-nanowire pitch is small. It is concluded that this growth regime is important for the array geometries typically used for optoelectronic and photovoltaic applications of nanowires. The growth rate under these conditions is also not constant with time, due to the growing nanowire mantle area. This result was confirmed by experiments in which dense arrays of InAs nanowires were grown and the nanowire growth rate was measured as a function of time. (C) 2013 Elsevier B.V. All rights reserved.
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| 4. |
- Borgström, Magnus, et al.
(författare)
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Fabrication and characterization of AlP-GaP core-shell nanowires
- 2011
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 324:1, s. 290-295
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Tidskriftsartikel (refereegranskat)abstract
- We report on the particle assisted synthesis of core-shell AlP-GaP nanowires by use of metal-organic vapor phase epitaxy. The core-shell approach is chosen such as to stabilize the AlP which is highly sensitive to water. The nanowires were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. These nanowires have an indirect band-gap and form a type II staggered heterojunction. By designed capping of the AlP cores by GaP, we find the nanowires to be stable for more than a year. (C) 2011 Elsevier B.V. All rights reserved.
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| 5. |
- Buchholt, Kristina, et al.
(författare)
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Growth and characterization of epitaxial Ti3GeC2 thin films on 4H-SiC(0001)
- 2012
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Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 343:1, s. 133-137
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial Ti3GeC2 thin films were deposited on 4 degrees off-cut 4H-SiC(0001) using magnetron sputtering from high purity Ti, C, and Ge targets. Scanning electron microscopy and helium ion microscopy show that the Ti3GeC2 films grow by lateral step-flow with {11 (2) over bar0} faceting on the SiC surface. Using elastic recoil detection analysis, atomic force microscopy, and X-Ray diffraction the films were found to be substoichiometric in Ge with the presence of small Ge particles at the surface of the film.
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| 6. |
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| 7. |
- Dou, Maofeng, et al.
(författare)
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Free exciton absorption in Ga1-xZnxN1-xOx alloys
- 2012
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 350:1, s. 17-20
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties of the Ga1-xZnxN1-xOx alloy (x=0.0, 0.25, 0.50, 0.75, and 1.00) are studied by first-principles means, employing the GW method to describe single-particle excitations and the Bethe-Salpeter equation (BSE) to model the two-particle exciton interactions. Intriguingly, we find that the band gaps of the Ga1-xZnxN1-xOx alloy are reduced significantly compared with that of bulk ZnO and GaN. By including the electron-hole interactions within the BSE approach, the imaginary part epsilon(2)(omega) of the dielectric function shows an optical absorption enhancement in the low energy region with the exciton peak below the band gap energy. By comparing the energy difference between the exciton absorption peaks E-ex and the energy gaps E-g, we qualitatively estimate that the strength of excitonic coupling is weaker in the Ga1-xZnxN1-xOx alloy than in both GaN and ZnO. Interestingly, the exciton absorption intensity increases with respect to ZnO content.
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| 8. |
- Fallberg, Anna, et al.
(författare)
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Phase stability and oxygen doping in the Cu-N-O system
- 2010
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Ingår i: Journal of Crystal Growth. - North Holland : Elsevier. - 0022-0248 .- 1873-5002. ; 312:10, s. 1779-1784
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Tidskriftsartikel (refereegranskat)abstract
- A growth stability diagram for the system Cu-N-O has been determined in the temperature range 250-500°C for a thermally activated CVD process, based on copper (II) hexafluoroacetylacetonate (Cu(hfac)2), NH3 and H2O. Without any addition of water only Cu3N was obtained. Addition of water introduces oxygen into the Cu3N structure to a maximum amount of 9 atomic % at a water/nitrogen molar ratio of 0.36 at 325 °C. Above this molar ratio Cu2O starts to deposit in addition to an oxygen doped Cu3N phase. Only Cu2O is deposited at a large excess of water. XPS and Raman spectroscopy indicated that the additional oxygen in the doped Cu3N structure occupies an interstitial position with a chemical environment similar to oxygen in Cu2O. The oxygen doping of the Cu3N phase did not influence the lattice parameter which was close to the bulk parameter of 3.814 Å. The film morphology varied markedly with both deposition temperature and water concentration in the vapour during deposition. Increasing the water concentration results in less faceted and textured films with smoother and more sphere like grains. The resistivity of the Cu3N films increased with increased oxygen content of the film and varied between 10-100 Ωcm (0 to 9 atomic% O). The optical band gap increased from 1.25 to 1.45 eV as the oxygen content increased (0 to 9 atomic %).
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| 9. |
- Forsberg, Kerstin, et al.
(författare)
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Crystallization of metal fluoride hydrates from mixed hydrofluoric and nitric acid solutions, Part I : Iron (III) and Chromium (III)
- 2010
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 312:16-17, s. 2351-2357
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Tidskriftsartikel (refereegranskat)abstract
- Crystallization from hydrofluoric acid/nitric acid solutions supersaturated with Fe(III) and Cr(III) has been investigated. Iron and chromium crystallizes into a solid solution in the form of Cr(Fe)F-3 center dot 3H(2)O, which is isostructural with CrF3 center dot 3H(2)O and alpha-FeF3 center dot 3H(2)O. By seeded isothermal desupersaturation experiments, the growth rate of beta-FeF3 center dot 3H(2)O crystals at 50 degrees C has been studied in hydrofluoric acid and nitric acid solutions containing Cr(III). It is found that the growth rate of beta-FeF3 center dot 3H(2)O is essentially uninfluenced by the presence of 5 g/kg Cr(III). At 50 degrees C and a supersaturation ratio of 2 (c(FeF3)(free)/c(s)(FeF3)(free)), the growth rate is (0.8-2.2) x 10(-11) m/s in 3 mol/(kg solution) HFfree and 3 mol/(kg solution) HNO3.
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| 10. |
- Forsberg, Kerstin, et al.
(författare)
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Crystallization of metal fluoride hydrates from mixed hydrofluoric and nitric acid solutions, part II : Iron (III) and nickel (II)
- 2010
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 312:16-17, s. 2358-2362
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Tidskriftsartikel (refereegranskat)abstract
- Crystallization of nickel fluoride hydrate from mixed pickle acid and the influence of Ni(II) on growth rate of beta-FeF3 center dot 3H(2)O have been studied. Iron and nickel crystallize into an unidentified Fe/Ni fluoride hydrate crystal having the overall mol ratio of Ni, Fe, and F equal to 1:2:8, which is in accordance with the number of fluoride ions needed to balance the positive charges of Ni and Fe. The most probable empirical formula of this material is (FeF3)(2)NiF2(H2O)(6-10). By seeded isothermal desupersaturation experiments, growth rate of beta-FeF3 center dot 3H(2)O crystals at 50 degrees C has been studied in a hydrofluoric acid and nitric acid solution containing Ni(II). It is found that the growth rate of beta-FeF3 center dot 3H(2)O is essentially uninfluenced by the presence of 4 g/kg Ni(II).
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