| 1. |
- 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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| 2. |
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- Hemmingsson, Carl, et al.
(författare)
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Optimization of low temperature GaN buffer layers for halide vapor phase epitaxy growth of bulk GaN
- 2013
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Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 366, s. 61-66
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Tidskriftsartikel (refereegranskat)abstract
- We have studied growth and self-separation of bulk GaN on c-oriented Al2O3 using low temperature (LT) GaN buffer layers. By studying the X-ray diffraction (XRD) signature for the asymmetric and symmetric reflections versus the LT-GaN thickness and V/III precursor ratio, we observe that the peak width of the reflections is minimized using a LT buffer thickness of ∼100–300 nm. It was observed that the V/III precursor ratio has a strong influence on the morphology. In order to obtain a smooth morphology, the V/III precursor ratio has to be more than 17 during the growth of the buffer layer. By using an optimized LT buffer layer for growth of a 20 μm thick GaN layer, we obtain a XRD peak with a full width at half maximum of ∼400 and ∼250 arcs for (002) and (105) reflection planes, respectively, and with a dark pit density of ∼2.2×108 cm−2. For layers thicker than 1 mm, the GaN was spontaneously separated and by utilizing this process, thick free freestanding 2″ GaN substrates were manufactured.
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| 8. |
- Hussain Ibupoto, Zafar, et al.
(författare)
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Well aligned ZnO nanorods growth on the gold coated glass substrate by aqueous chemical growth method using seed layer of Fe3O4 and Co3O4 nanoparticles
- 2013
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Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 368, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- In this study, Fe3O4 and Co3O4 nanoparticles were prepared by co-precipitation method and sol-gel method respectively. The synthesised nanoparticles were characterised by X-ray diffraction [XRD] and Raman spectroscopy techniques. The obtained results have shown the nanocrystalline phase of obtained Fe3O4 and Co3O4 nanoparticles. Furthermore, the Fe3O4 and Co3O4 nanoparticles were used as seed layer for the fabrication of well-aligned ZnO nanorods on the gold coated glass substrate by aqueous chemical growth method. Scanning electron microscopy (SEM), high resolution transmission electron microscopy [HRTEM], as well as XRD and energy dispersive X-ray techniques were used for the structural characterisation of synthesised ZnO nanorods. This study has explored highly dense, uniform, well-aligned growth pattern along 0001 direction and good crystal quality of the prepared ZnO nanorods. ZnO nanorods are only composed of Zn and O atoms. Moreover, X-ray photoelectron spectroscopy was used for the chemical analysis of fabricated ZnO nanorods. In addition, the structural characterisation and the chemical composition study and the optical investigation were carried out for the fabricated ZnO nanorods and the photoluminescence [PL] spectrum have shown strong ultraviolet (UV) peak at 381 nm for Fe3O4 nanoparticles seeded ZnO nanorods and the PL spectrum for ZnO nanorods grown with the seed layer of Co3O4 nanoparticles has shown a UV peak at 382 nm. The green emission and orange/red peaks were also observed for ZnO nanorods grown with both the seed layers. This study has indicated the fabrication of well aligned ZnO nanorods using the one inorganic nanomaterial on other inorganic nanomaterial due to their similar chemistry.
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| 9. |
- Kakanakova-Gueorgieva, Anelia, et al.
(författare)
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High-quality AlN layers grown by hot-wall MOCVD at reduced temperatures
- 2012
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Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 338:1, s. 52-56
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Tidskriftsartikel (refereegranskat)abstract
- We report on a growth of AlN at reduced temperatures of 1100 C and 1200 C in a horizontal-tube hot-wall metalorganic chemical vapor deposition reactor configured for operation at temperatures of up to 15001600 C and using a joint delivery of precursors. We present a simple route - as viewed in the context of the elaborate multilayer growth approaches with pulsed ammonia supply - for the AlN growth process on SiC substrates at the reduced temperature of 1200 C. The established growth conditions in conjunction with the particular in-situ intervening SiC substrate treatment are considered pertinent to the accomplishment of crystalline, relatively thin, ∼700 nm, single AlN layers of high-quality. The feedback is obtained from surface morphology, cathodoluminescence and secondary ion mass spectrometry characterization.
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| 10. |
- Kukli, Kaupo, et al.
(författare)
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Structure and morphology of Ru films grown by atomic layer deposition from 1-ethyl-1 '-methyl-ruthenocene
- 2010
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 312:12-13, s. 2025-2032
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Tidskriftsartikel (refereegranskat)abstract
- Ru thin films were grown on TiO2, Al2O3, HfO2, and ZrO2 films as well as on HF-etched silicon and SiO2-covered silicon by atomic layer deposition from 1-ethyl-1'-methyl-ruthenocene, (CH3C5H4) (C2H5C5H4)Ru, and oxygen. The growth of Ru was obtained and characterized at temperatures ranging from 250 to 325 degrees C. On epitaxial rutile, highly oriented growth of Ru with hexagonal structure was achieved, while on other substrates the films possessed nonoriented hexagonal structure. Ruthenium oxide was not detected in the films. The lowest resistivity value obtained for 5.0-6.6 nm thick films was 26 mu Omega cm. The conductivity of the films depended somewhat on the deposition cycle time parameters and, expectedly, more strongly on the amount of deposition cycles. Increase in the deposition temperature of underlying metal oxide films increased the conductivity of Ru layers.
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