| 1. |
- Alm, Oscar, et al.
(författare)
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Tungsten oxide nanoparticles synthesised by laser assisted homogeneous gas-phase nucleation
- 2005
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 247:1-4, s. 262-267
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten oxide nanoparticles were generated by excimer (ArF) laser assisted chemical vapor deposition from WF6/H2/O2/Ar gas mixtures. The deposited particles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The deposition rate as a function of the partial pressures of the reactants and of the laser fluence was measured by X-ray fluorescence spectroscopy. The mean diameter of the deposited tungsten oxide particles varied with the experimental parameters and was typically 23 nm. Particles with a higher degree of crystallinity were observed at a laser fluence exceeding 130 mJ/cm2, and X-ray amorphous particles were obtained below 110 mJ/cm2. The amorphous tungsten oxide had a stoichiometry ranging from WO2.7 to WO3. Deposits were formed only when hydrogen was present in the gas mixture.
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| 2. |
- Aroutiounian, V., et al.
(författare)
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Fluctuation-enhanced gas sensing
- 2009
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Ingår i: Procedia Chemistry. - : Elsevier BV. - 1876-6196.
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Konferensbidrag (refereegranskat)abstract
- The sensitivity of gas sensors was earlier measured by classical method-comparison the resistance of sensors in gas media and air. Here we reported results of the study of low-frequency noise characteristics of sensors. We compare data for different Figaro TGS sensors as well as our sol-gel H-2 tin dioxide and porous silicon sensors. The study was performed in dry air and in a mix of dry air with carbon monoxide, hydrogen and alcohol of different concentrations. Higher sensitivity of spectral dependence of noise (SDN) to gas concentration in comparison with classical method of the measurements of gas sensing by a change in the Ohmic resistance part of current-voltage characteristics of samples allows using such SND powerful method for determination of gas concentration in the air or environment.
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| 3. |
- Aroutiounian, Vladimir M., et al.
(författare)
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Noise spectroscopy of gas sensors
- 2008
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 8:5-6, s. 786-790
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Tidskriftsartikel (refereegranskat)abstract
- We study current-voltages and low-frequency noise characteristics of the metal-porous silicon-silicon single crystal-metal structure with 50% and 73% porosity of porous silicon. The study is performed in dry air and in a mix of dry air with carbon monoxide of different concentrations. The Hooge noise parameter alpha(H) and the parameter gamma in the frequency dependence of the noise voltage spectral density S-U (f) were determined from experimental data. High sensitivity of spectral dependence of noise to gas concentration allows offering powerful method for determination of gas concentration in the air or environment.
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| 4. |
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| 5. |
- Avendano, Esteban, et al.
(författare)
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Coloration Mechanism in Proton-Intercalated Electrochromic Hydrated NiOy and Ni1-xVxOy Thin Films
- 2009
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 156:8, s. p132-p138
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Tidskriftsartikel (refereegranskat)abstract
- Electrochromic (EC) films of nickel oxide, with and without vanadium, were prepared by reactive dc magnetron sputtering. They were characterized by electrochemical and optical measurements and studied by X-ray photoelectron spectroscopy (PES) using synchrotron radiation. The films were analyzed under as-deposited conditions and after bleaching/coloration by insertion/extraction of protons from a basic solution and ensuing charge stabilization. Optical measurements were consistent with a coloration process due to charge-transfer transitions from Ni2+ to Ni3+ states. The PES measurements showed a higher concentration of Ni3+ in the colored films. Moreover, two peaks were present in the O 1s spectra of the bleached film and pointed to contributions of Ni(OH)(2) and NiO. The changes in the O 1s spectra upon coloration treatment indicate the presence of Ni2O3 in the colored film and necessitated an extension of the conventional model for the mechanism of EC coloration. The model involves not only proton extraction from nickel hydroxide to form nickel oxyhydroxide but also participation of NiO in the coloration process to form Ni2O3.
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| 6. |
- Avendano, Esteban, et al.
(författare)
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Sputter Deposited Electrochromic Films and Devices Based on These : Progress on nickel-oxide-based films
- 2007
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 138:2, s. 112-117
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Tidskriftsartikel (refereegranskat)abstract
- This paper introduces electrochromic (EC) devices, capable of changing their optical absorption under charge insertion/extraction, and some of the required materials. Special attention is given to EC nickel-oxide-based films, for which we discuss sputter deposition and ensuing optical and structural properties. The paper is concluded with some recent results for practical foil-based devices.
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| 7. |
- Backholm, Jonas, et al.
(författare)
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Iridium-based oxides: Recent advances in coloration mechanism, structural and morphological characterization
- 2008
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 92:2, s. 91-96
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Tidskriftsartikel (refereegranskat)abstract
- Films of iridium-tantalum oxide and iridium oxide have been prepared by sputtering and studied regarding their structure and electrochemical properties. X-ray diffraction and transmission electron microscopy showed an average grain size of 3-4 nm for both films. Point energy dispersive X-ray spectrometry showed an inhomogeneous distribution of iridium and tantalum indicating that the iridium-tantalum oxide may be a mixture of small IrO2 and Ta2O5 grains, which is consistent with the determined composition IrTa1.4O5.6. X-ray photoelectron spectroscopy gave valuable information on the stabilization process of the as-deposited films involving an uptake of oxygen, and on a coloration mechanism only including protons.
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