| 1. |
- Gonzalez-Borrero, P. P., et al.
(författare)
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Optical band-gap determination of nanostructured WO3 film
- 2010
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:6
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Tidskriftsartikel (refereegranskat)abstract
- The optical band-gap energy of a nanostructured tungsten trioxide film is determined using the photoacoustic spectroscopy method under continuous light excitation. The mechanism of the photoacoustic signal generation is discussed. The band-gap energy is also computed by other methods. The absorption coefficient as well as the band-gap energy of three different crystal structures of tungsten trioxide is calculated by a first-principles Green's function approach using the projector augmented wave method. The theoretical study indicates that the cubic crystal structure shows good agreement with the experimental data.
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| 2. |
- Hu, Shuanglin, et al.
(författare)
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Optical properties of Mg-doped VO2 : Absorption measurements and hybrid functional calculations
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:20, s. 201902-
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Tidskriftsartikel (refereegranskat)abstract
- Mg-doped VO2 thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < <(h)over bar>omega < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.
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| 3. |
- Lansåker, Pia C, et al.
(författare)
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Characterization of gold nanoparticle films : Rutherford backscattering spectroscopy, scanning electron microscopy with image analysis, and atomic force microscopy
- 2014
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 4:10, s. 107101-
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Tidskriftsartikel (refereegranskat)abstract
- Gold nanoparticle films are of interest in several branches of science and technology, and accurate sample characterization is needed but technically demanding. We prepared such films by DC magnetron sputtering and recorded their mass thickness by Rutherford backscattering spectroscopy. The geometric thickness d(g)-from the substrate to the tops of the nanoparticles-was obtained by scanning electron microscopy (SEM) combined with image analysis as well as by atomic force microscopy (AFM). The various techniques yielded an internally consistent characterization of the films. In particular, very similar results for d(g) were obtained by SEM with image analysis and by AFM.
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| 4. |
- Li, Shu-Yi, et al.
(författare)
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Bandgap widening in thermochromic Mg-doped VO2 thin films : Quantitative data based on optical absorption
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:16, s. 161907-
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Tidskriftsartikel (refereegranskat)abstract
- Thermochromic Mg-doped VO2 films were deposited by reactive direct current magnetron sputtering onto heated glass and carbon substrates. Elemental compositions were inferred from Rutherford backscattering. Optical bandgaps were obtained from spectral transmittance and reflectance measurements-from both the film side and the back side of the samples-and ensuing determination of absorption coefficients. The bandgap of Mg-doped films was found to increase by 3.9 +/- 0.5 eV per unit of atom ratio Mg/(Mg + V) for 0 < Mg/(Mg + V) < 0.21. The presence of similar to 0.45 at. % Si enhanced the bandgap even more.
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| 5. |
- Lykissa, Iliana, et al.
(författare)
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Electronic density-of-states of amorphous vanadium pentoxide films : Electrochemical data and density functional theory calculations
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:18, s. 183701/1-/5
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of V2O5 were prepared by sputter deposition onto transparent and electrically conducting substrates and were found to be X-ray amorphous. Their electrochemical density of states was determined by chronopotentiometry and displayed a pronounced low-energy peak followed by an almost featureless contribution at higher energies. These results were compared with density functional theory calculations for amorphous V2O5. Significant similarities were found between measured data and computations; specifically, the experimental low-energy peak corresponds to a split-off part of the conduction band apparent in the computations. Furthermore, the calculations approximately reproduce the experimental band gap observed in optical measurements.
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| 6. |
- Waita, Sebastian M., et al.
(författare)
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Electron transport and recombination in dye sensitized solar cells fabricated from obliquely sputter deposited and thermally annealed TiO2 films
- 2007
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657 .- 0022-0728 .- 1873-2569. ; 605:2, s. 151-156
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Tidskriftsartikel (refereegranskat)abstract
- Dye sensitized solar cells based on annealed titanium dioxide films prepared by oblique reactive DC magnetron sputtering have been investigated in detail. Electron transport and recombination were studied using intensity-modulated photocurrent and photovoltage spectroscopy. Electron transport time as well as lifetime were found to increase upon lowering of the light intensity and to increase upon increasing the thickness of the TiO2 film. The properties are very similar to those observed for solar cells based on colloidal TiO2 films despite the morphologies being very different. In all cases, films are composed of a porous assembly of TiO2 nanocrystals. Grain boundaries with associated trap and/or energy barriers may explain the observed transport properties.
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