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| 2. |
- da Silva, A. Ferreira, et al.
(författare)
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Growth, Electrical and Optical Properties of SnO2:F on ZnO, Si and Porous Si Structures
- 2009
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Ingår i: NANOTECH CONFERENCE & EXPO 2009, VOL 1, TECHNICAL PROCEEDINGS. - : CRC PRESS-TAYLOR & FRANCIS GROUP. - 9781439817827 ; , s. 352-
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Konferensbidrag (refereegranskat)abstract
- In this work we have analyzed the optical absorption of the ZnO and SnO2:F (FTO) films and applied them in porous silicon light-emitting diodes. The absorption and energy gap were calculated by employing the projector augmented wave method [1] within the local density approximation and with a modeled on-site self-interaction-like correction potential within the LDA+U-S/C [2]. Experiment and theory show a good agreement when the optical absorption and optical energy gap are considered. A layer of FTO is deposited by spray pyrolysis on top of porous Si (PSi) or ZnO/(PSi) in order to make the LEDs. The morphology and roughness of the films are analyzed by Atomic Force Microscopy before and after the FTO deposition. The electrical and optical properties are studied by characteristics curves J x V, and electroluminescence intensity versus bias.
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| 4. |
- 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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| 7. |
- Kaambre, T., et al.
(författare)
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Resonant inelastic X-ray scattering at the Be 1s edge in BeO
- 2007
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 156, s. 299-302
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Tidskriftsartikel (refereegranskat)abstract
- We present the resonant inelastic X-ray scattering (RIXS) spectra of BeO at the Be 1s photoabsorption edge. The RIXS spectra excited in the vicinity of the core exciton resonance show two principal features: the scattering on a valence exciton (which at higher excitation energies verges into the characteristic K alpha emission), and a remarkably strong energy loss side-band to the elastic scattering peak, which has a maximum width of 6 eV and has intensity, at resonance, comparable to the valence scattering. The energy loss side-band appears to result from rapid lattice relaxation at the absorption site on the X-ray scattering time-span. (c) 2006 Elsevier B.V. All rights reserved.
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| 8. |
- Kikas, A, et al.
(författare)
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Resonant inelastic X-ray scattering at the K edge of oxygen and fluorine in insulators
- 2005
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 144-147, s. 845-848
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Tidskriftsartikel (refereegranskat)abstract
- Here we present the results of a study of the electronic structure using the resonant inelastic scattering process at the F 1s photoabsorption edge in LiF and O 1s edge of MgO crystals. In case of excitations in the sub-threshold region, the Raman-type linear dispersion of X-ray fluorescence peak was observed for the studied compounds. In LiF, the narrowing of the X-ray fluorescence peak is observed at pre-threshold excitation, which can be related to the creation of a core exciton, but no core excitons were identified in MgO.
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| 9. |
- Ruus, R., et al.
(författare)
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Cs 3d absorption and resonant photoemission study of caesium halogenides
- 2005
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Ingår i: Physica Scripta. - 0031-8949. ; T115, s. 396-398
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Tidskriftsartikel (refereegranskat)abstract
- The highly localized 4f electrons play an important role in forming of the electronic structure and properties of compounds. The 3d photoabsorption and resonant decay spectra of Cs halides represent an interesting case showing both the localized and spatially extended f wave function features. We present and discuss the Cs 3d X-ray absorption and resonant photoelectron emission spectra of the Cs halides. The Cs 3d absorption spectra exhibit a strong atom-like shape resonance behavior, solid-state effects play a minor role. The appearance of the spectral features, which are intrinsic to a localized state, in the decay spectra show that the Cs 3d photoelectron, temporally and spatially trapped in the Cs 3d shape resonance due to the potential barrier for epsilon f electrons near threshold, has substantially localized nature.
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| 10. |
- Al-Hilli, Safaa, 1965, et al.
(författare)
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Zinc oxide nanorods grown on two-dimensional macroporous periodic structures and plane Si as a pH sensor
- 2008
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 103:1, s. 014302-014309
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Tidskriftsartikel (refereegranskat)abstract
- pH determination is a strong prerequisite for many biochemical and biological processes. We used two methods, namely, the electrochemical potential method (experimental) and site binding method (theoretical), to study the sensitivity of zinc oxide (ZnO) nanorods grown on two-dimensional macroporous periodic structures (2DMPPS) (p-and n-type) and plane n-type Si substrates for use as an intracellular pH sensing device. The dimension of these nanorods varied in radius between 50 and 300 nm and lengths of 1–10 μm. We found that the sensitivity of ZnO nanorods increases with reductions in size, from 35 mV/pH for D = 300 nm and L = 10 μm, to 58 mV/pH for D = 50 nm and L = 1 μm, using the site binding model. The experimental electrochemical potential difference for the ZnO nanorods working electrode versus Ag/AgCl reference electrode showed a high sensitivity range for ZnO nanorods grown on 2DMPPS n-Si substrate as compared to plane n-Si at room temperature for pH ranging from 4 to 12 in buffer and NaCl solutions
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