| 51. |
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| 52. |
- Cindemir, Umut, et al.
(författare)
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Porous Nickel Oxide Film Sensor for Formaldehyde
- 2014
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Ingår i: INERA Workshop: Transition Metal Oxides as Functional Layers in Smart windows and Water Splitting Devices / Parallel session of the 18th International School on Condensed Matter Physics. - : IOP Publishing. ; , s. UNSP 012012-
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Konferensbidrag (refereegranskat)abstract
- Formaldehyde is a volatile organic compound and a harmful indoor pollutant contributing to the "sick building syndrome". We used advanced gas deposition to fabricate highly porous nickel oxide (NiO) thin films for formaldehyde sensing. The films were deposited on Al2O3 substrates with prefabricated comb-structured electrodes and a resistive heater at the opposite face. The morphology and structure of the films were investigated with scanning electron microscopy and X-ray diffraction. Porosity was determined by nitrogen adsorption isotherms with the Brunauer-Emmett-Teller method. Gas sensing measurements were performed to demonstrate the resistive response of the sensors with respect to different concentrations of formaldehyde at 150 degrees C.
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| 53. |
- Cindemir, Umut, et al.
(författare)
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Porous Nickel Oxide Sensor for Formaldehyde Detection
- 2014
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Ingår i: European Materials Society (E-MRS) Spring Meeting, Lille, France, May 26-30, 2014..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Formaldehyde is a volatile organic compound, which is a harmful indoor pollutant, causing sick building syndrome (SBS) and is released from household and building materials. Since higher concentrations of formaldehyde are considered to be carcinogenic, monitoring them indoors is of great importance. Advanced gas deposition has here been used to fabricate highly porous nickel oxide (NiO) thin films for formaldehyde sensing. The films were deposited on Al2O3 substrates with prefabricated comb-structured electrodes, and a resistive heater at the opposite face. The morphology of the films was investigated with scanning electron microscopy, and the porosity was determined by nitrogen adsorption isotherms with the Brunauer-Emmett-Teller method. The particle size was found to be less than 10 nm, as determined by x-ray diffraction. X-ray photoelectron spectroscopy of the NiO films was also done. Gas sensing measurements were done using a total gas flow rate of 200 ml/min. Resistivity values of sensors were recorded with formaldehyde diluted in synthetic air. Sensor resistances were recorded at 50 ppm, 25ppm, 10ppm and 5 ppm formaldehyde concentration. NiO films showed promising formaldehyde gas sensing properties implying lower levels of detection limit.
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| 54. |
- Cindemir, Umut, et al.
(författare)
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Sputter-Deposited Indium-Tin Oxide Thin Films for Acetaldehyde Gas Sensing
- 2016
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Ingår i: Coatings. - : MDPI AG. - 2079-6412. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- Reactive dual-target DC magnetron sputtering was used to prepare In-Sn oxide thin films with a wide range of compositions. The films were subjected to annealing post-treatment at 400 degrees C or 500 degrees C for different periods of time. Compositional and structural characterizations were performed by X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Rutherford backscattering and scanning electron microscopy. Films were investigated for gas sensing at 200 degrees C by measuring their resistance response upon exposure to acetaldehyde mixed with synthetic air. We found that the relative indium-to-tin content was very important and that measurable sensor responses could be recorded at acetaldehyde concentrations down to 200 ppb, with small resistance drift between repeated exposures, for both crystalline SnO2-like films and for amorphous films consisting of about equal amounts of In and Sn. We also demonstrated that it is not possible to prepare crystalline sensors with intermediate indium-to-tin compositions by sputter deposition and post-annealing up to 500 degrees C.
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| 55. |
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| 56. |
- Cindemir, Umut
(författare)
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Thin films for indoor air monitoring : Measurements of Volatile Organic Compounds
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Volatile organic compounds (VOCs) in the indoor air have adverse effects on the dwellers residing in a building or a vehicle. One of these effects is called sick building syndrome (SBS). SBS refers to situations in which the users of a building develop acute health effects and discomfort depending on the time they spend inside some buildings without having any specific illness. Furthermore, monitoring volatile organic compounds could lead to early diagnosis of specific illnesses through breath analysis. Among those VOCs formaldehyde, acetaldehyde can be listed.In this thesis, VOC detecting thin film sensors have been investigated. Such sensors have been manufactured using semiconducting metal oxides, ligand activated gold nanoparticles and Graphene/TiO2 mixtures. Advanced gas deposition unit, have been used to produce NiO thin films and Au nanoparticles. DC magnetron sputtering has been used to produce InSnO and VO2 thin film sensors. Graphene/TiO2 sensors have been manufactured using doctor-blading.While presenting the results, first, material characterization details are presented for each sensor, then, gas sensing results are presented. Morphologies, crystalline structures and chemical properties have been analyzed using scanning electron microscopy, X-ray diffraction and X-ray photo electron spectroscopy. Furthermore, more detailed analyses have been performed on NiO samples using extended X-ray absorption fine structure method and N2 adsorption measurements. Gas sensing measurements were focused on monitoring formaldehyde and acetaldehyde. However, responses ethanol and methane were measured in some cases to monitor selectivity. Graphene/TiO2 samples were used to monitor NO2 and NH3. For NiO thin film sensors and Au nano particles, fluctuation enhanced gas sensing is also presented in addition to conductometric measurements.
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| 57. |
- Coll, M., et al.
(författare)
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Towards Oxide Electronics: a Roadmap
- 2019
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 482, s. 1-93
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Tidskriftsartikel (refereegranskat)abstract
- At the end of a rush lasting over half a century, in which CMOS technology has been experiencing a constant and breathtaking increase of device speed and density, Moore’s law is approaching the insurmountable barrier given by the ultimate atomic nature of matter. A major challenge for 21st century scientists is finding novel strategies, concepts and materials for replacing silicon-based CMOS semiconductor technologies and guaranteeing a continued and steady technological progress in next decades. Among the materials classes candidate to contribute to this momentous challenge, oxide films and heterostructures are a particularly appealing hunting ground. The vastity, intended in pure chemical terms, of this class of compounds, the complexity of their correlated behaviour, and the wealth of functional properties they display, has already made these systems the subject of choice, worldwide, of a strongly networked, dynamic and interdisciplinary research community. Oxide science and technology has been the target of a wide four-year project, named Towards Oxide-Based Electronics (TO-BE), that has been recently running in Europe and has involved as participants several hundred scientists from 29 EU countries. In this review and perspective paper, published as a final deliverable of the TO-BE Action, the opportunities of oxides as future electronic materials for Information and Communication Technologies ICT and Energy are discussed. The paper is organized as a set of contributions, all selected and ordered as individual building blocks of a wider general scheme. After a brief preface by the editors and an introductory contribution, two sections follow. The first is mainly devoted to providing a perspective on the latest theoretical and experimental methods that are employed to investigate oxides and to produce oxide-based films, heterostructures and devices. In the second, all contributions are dedicated to different specific fields of applications of oxide thin films and heterostructures, in sectors as data storage and computing, optics and plasmonics, magnonics, energy conversion and harvesting, and power electronics.
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| 58. |
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| 59. |
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| 60. |
- Engfeldt, Johnny D., et al.
(författare)
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GLAZING FOR ENERGY EFFICIENT BUILDINGS: : The Almost Forgotten Role of Angular-Dependent Solar Transmittance
- 2020
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Ingår i: Society of Vacuum Coaters Bulletin. - : Society of Vacuum Coaters. ; :spring, s. 72-78
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Tidskriftsartikel (refereegranskat)abstract
- Glazing for energy efficient buildings comprises multi-pane units with surface coated glass. According to today’s standards, glazing is characterized by optical measurements at normal light incidence. Here we show that this prerequisite is grossly inadequate for common vertical glazing, in particular regarding solar transmittance and total energy transmittance (g-value). We present data on spectral and angular-dependent transmittance in the 300–2500-nm wavelength range for several types of glass samples with hard (tin-oxide-based) and soft (silver-based) coatings. Furthermore, we use standard procedures to compute g-values for triple-pane glazing embodying such glass and find that the g-value at 60° off-normal angle typically is as low as 65–68% of the g-value for normal incidence. This difference is essential for assessing the energy efficiency of modern buildings and highlights that the glazing’s angularity must be accounted for.
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