| 1. |
- Ferreira Da Silva, A., et al.
(författare)
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Growth, optical characterization and modeling of ZnO nanorods on Si, SiC and macroporous si structure
- 2009
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Ingår i: Technical Proceedings of the 2009 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2009. - : CRC Press. - 9781439817834 - 9781439817841 ; , s. 206-209
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Konferensbidrag (refereegranskat)abstract
- Zinc Oxide (ZnO) and Silicon Carbide (SiC) are prominent materials with large applicability such as optoelectronic nanodevices and for instance ultraviolet detectors. There is lack of important information about optical transitions beyond the indirect band gap energy (BGE) of 4H-SÍC and even more for ZnO direct BGE grown on the former material. Using vapor-liquid-solid and the aqueous chemical growth methods we have grown ZnO nanorods on different substrates, such as quartz, n- and p-type porous silicon, and n-type 4H-SÍC. Scanning electron microscopy (SEM) was employed to compare sample morphologies. The absorption was calculated employing a projector augmented wave (PAW) method. The measured absorption of ZnO nanorods, on different substrates, is lower than that observed for ZnO films on quartz substrate, in the low energy spectral range. It is observed a strong effect of 4H-SÍC substrates on ZnO nanorod properties. Experiment and theory show a good agreement when the shape of the optical absorption is considered for both materials.
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| 2. |
- Minaev, B., et al.
(författare)
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DFT calculations of IR and Raman spectra of Ru(bpy)2(CN) 2 complex
- 2009
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Ingår i: Technical Proceedings of the 2009 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2009. - : CRC Press. - 9781439817834 - 9781439817841 ; , s. 152-155
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Konferensbidrag (refereegranskat)abstract
- Harvesting energy directly from sunlight using photovoltaic technology is an essential component of the future global energy production programs [1]. Photovoltaic devices, or solar cells, are based on the photoelectric effect, in which the incoming solar photons are absorbed in a sensitized semiconductor material freeing electric charges that are used to energize an external circuit [2]. The solar cells on the bases of nanocrystalline TiO2 are usually sensitized by metal-organic dyes such as Ru-complexes with phenylpyridine and bipyridine ligands. The incident photon to current conversion efficiency (IPCCE) in the wavelength region 400-600 nm can be rather high [1, 2]. In order to improve the IPCCE value the heavier metal ions could be tested. Such sensitizers as coumarin, porphyrins, chlorophyll derivatives, antenna-sentsitizer polynuclear complexes and eosin have been studied and reported to be less efficient than the most effective Ru-based sensitizing dyes, called the black dye (BD) and N3 dye [2-4], used for the nanocrystalline TiO2 solar cell. In this paper we are planning to understand the IPCE of a new dye-sensitizer in order to predict the higher absorption efficiency to solar spectrum and higher electron transfer rate from redox systems to oxidized dye. Some simple Ru(II)(bpy)2(CN)2 complex is studied by DFT method with optimized structure and vibrational analysis in order to predict the role of vibronic perturbations in spectra and interface electron transfer rate.
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| 3. |
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| 4. |
- Ferreira da Silva, Antonio, et al.
(författare)
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Growth, Optical Characterization and Modelling of ZnO Nanorods on Si, SiC and Macroporous Si Structure
- 2009
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Ingår i: Nanotech 2009 Vol. 3Nanotechnology 2009: Biofuels, Renewable Energy, Coatings, Fluidics and Compact Modeling. - Austin, TX, USA : Nano Science and Technology Institute. - 9781439817841 ; , s. 206-209
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Zinc Oxide (ZnO) and 4H-SiC are prominent materials with large applicability such as optoelectronic nanodevices and for instance ultraviolet detectors. There is lack of more information about optical transitions beyond the indirect band gap energy (BGE) of 4H-SiC and even more for ZnO direct BGE grown on the former material. Using the vapor-liquid-solid and the aqueous chemical growth methods we have grown ZnO nanorods on different substrates, such as quartz, n- and p-type silicon porous silicon and n-type 4H-SiC. The Scanning electron microscopy (SEM) are shown and compared for all samples. We have calculated the absorption and energy gap by employing a first-principle and a full-potential linearized augmented plane-wave (FPLAPW) method within the local density approximation (LDA). The absorption of ZnO nanorods, on different substrates, is lower than that of quartz substrate when photon energy is low. It is shown the strong effect of 4H-SiC on ZnO nanorods. Experiment and theory show a good aggreement when the optical energy gap is considered for both materials.
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