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377 results on '"Nilsen, Ola"'

2. Surface Forces Apparatus Measurements of Interactions between Rough and Reactive Calcite Surfaces

Author

Dziadkowiec, Joanna, Javadi, Shaghayegh, Bratvold, Jon E., Nilsen, Ola, and Røyne, Anja

Subjects
Condensed Matter - Materials Science, Condensed Matter - Soft Condensed Matter
Abstract

Nm-range forces acting between calcite surfaces in water affect macroscopic properties of carbonate rocks and calcite-based granular materials, and are significantly influenced by calcite surface recrystallization. We suggest that the repulsive mechanical effects related to nm-scale surface recrystallization of calcite in water could be partially responsible for the observed decrease of cohesion in calcitic rocks saturated with water. Using the Surface Forces Apparatus (SFA), we simultaneously followed the calcite reactivity and measured the forces in water in two surface configurations: between two rough calcite surfaces (CC), or between rough calcite and a smooth mica surface (CM). We used nm-scale rough, polycrystalline calcite films prepared by Atomic Layer Deposition (ALD). We measured only repulsive forces in CC in CaCO$_3$-saturated water, which was related to hydration effects and/or roughness. Velocity-dependent adhesion forces were measured in monoethylene glycol (MEG) for relatively smooth surfaces in CC. Adhesive or repulsive forces were measured in CM in CaCO$_3$-saturated water depending on the calcite roughness, and the adhesion was likely enhanced by electrostatic effects. The pull-off adhesive force in CM became stronger with time and this increase was correlated with a decrease of roughness at contacts, which parameter could be estimated from the measured force-distance curves. Reactivity of calcite was affected by mass transport across nm to ${\mu}$m-thick gaps between the surfaces. Major roughening was observed only for the smoothest calcite films, where the gaps between the two opposing surfaces were nm-thick over ${\mu}$m-sized areas, and led to a force of crystallization that could overcome confining pressures of the order of MPa., Comment: This document is the unedited Authors version of a Submitted Work that was subsequently accepted for publication in Langmuir copyright American Chemical Society after peer review. To access the final edited and published work see https://pubs.acs.org/articlesonrequest/AOR-KgDqy7WXE38JGksBdMVx

Published
2019
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10. Comparison of near-interface traps in Al$_2$O$_3$/4H-SiC and Al$_2$O$_3$/SiO$_2$/4H-SiC structures

Author

Avice, Marc, Grossner, Ulrike, Pintilie, Ioana, Svensson, Bengt G., Nilsen, Ola, and Fjellvag, Helmer

Subjects
Condensed Matter - Materials Science
Abstract

Aluminum oxide (Al2O3) has been grown by atomic layer deposition on n-type 4H-SiC with and without a thin silicon dioxide (SiO2) intermediate layer. By means of Capacitance Voltage and Thermal Dielectric Relaxation Current measurements, the interface properties have been investigated. Whereas for the samples with an interfacial SiO2 layer the highest near-interface trap density is found at 0.3 eV below the conduction band edge, Ec, the samples with only the Al2O3 dielectric exhibit a nearly trap free region close to Ec. For the Al2O3/SiC interface, the highest trap density appears between 0.4 to 0.6 eV below Ec. The results indicate the possibility for SiC-based MOSFETs with Al2O3 as the gate dielectric layer in future high performance devices., Comment: 3 figures. Applied Physics Letters, accepted for publication

Published
2006
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11. Interrogation of the Interfacial Energetics at a Tantalum Nitride/Electrolyte Heterojunction during Photoelectrochemical Water Splitting by Operando Ambient Pressure X-ray Photoelectron Spectroscopy

Author

Dahl, Øystein, primary, Sunding, Martin Fleissner, additional, Killi, Veronica, additional, Svenum, Ingeborg-Helene, additional, Grandcolas, Mathieu, additional, Andreassen, Magnus, additional, Nilsen, Ola, additional, Thøgersen, Annett, additional, Jensen, Ingvild Julie Thue, additional, and Chatzitakis, Athanasios, additional

Published
2023
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15. Perylenes, Porphyrins, and Other Large Dye Molecules for Molecular Layer Deposition.

Author

Hansen, Per‐Anders, Holm Sørensen, Silje, Desbois, Nicolas, Gros, Claude P., and Nilsen, Ola

Subjects
PORPHYRINS, PERYLENE, MOLECULES, OPTICAL rotation, ATOMIC layer deposition, METALLOPORPHYRINS, OPTICAL properties
Abstract

Molecular layer deposition (MLD) is an incredibly powerful and flexible tool for designing completely new materials with novel and unique properties. The low temperature layer‐by‐layer approach and the use of highly reactive reactants allows one to combine vastly different organic and inorganic species and construct nanostructures with subnanometer precision. If not limited by the volatility of the reactants involved, the possibilities will be endless. This is most notable for the organic building blocks where an overall low volatility severely limits the toolbox of large molecules with interesting optical and electrical properties such as red‐ox activity and optical conversion. In this work, different strategies for molecular design of large molecules are investigated that allow vaporization while still having the necessary reactivity for MLD growth. Using these strategies, film growth with perylene and porphyrin derivatives, both molecules well known for their functional and optical properties are successfully achieved. With this knowledge, there is an opening to include much larger and more complex organic molecules into the world of vapor phase chemistry. [ABSTRACT FROM AUTHOR]

Published
2024
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36. Investigation of the Atomic Layer Deposition of the Titanium Dioxide (TiO 2) Film as pH Sensor Using a Switched Capacitor Amplifier.

Author

Nematzadeh, Mozhdeh, Nilsen, Ola, Häfliger, Philipp Dominik, and Killi, Veronica Anne-Line Kathrine

Subjects
ATOMIC layer deposition, CAPACITOR switching, TITANIUM dioxide, CHARGE transfer, SURFACE roughness
Abstract

The electrical and chemical properties of the titanium dioxide (TiO2) coated spirals grown by the atomic layer deposition (ALD) technique in two different temperatures of 150 °C and 300 °C are studied. The thickness of the TiO2 layers studied are 20, 40, and 80 nm. A switched capacitor amplifier is used to investigate the pH response and the capacitance of the samples. It is found that the performance of the TiO2 samples depends on either the thickness or the deposition temperature due to the differences in the physical properties of the oxide layer such as surface roughness and film density. The high temperature samples are more crystalline, whereas the low temperature samples are more amorphous. Since there is a low pass filter effect in the electrolyte–sample interface, the TiO2 coated samples show the better response to the pH change for the high temperature samples as the sensor surface area for binding the hydrogen ions is larger and the charge transfer resistance is smaller. Furthermore, more roughness on the surface can be obtained by increasing the thickness, which reduces the charge transfer resistance. In this study, the 80 nm sample deposited at 300 °C gives the best pH response of 40 mV/pH. [ABSTRACT FROM AUTHOR]

Published
2022
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37. Single-step approach to sensitized luminescence through bulk-embedded organics in crystalline fluorides

Author

Hansen, Per Anders, Zikmund, Tomas, Yu, Ting, Kvalvik, Julie Nitsche, Aarholt, Thomas, Prytz, Øystein, Meijerink, Andries, Nilsen, Ola, Hansen, Per Anders, Zikmund, Tomas, Yu, Ting, Kvalvik, Julie Nitsche, Aarholt, Thomas, Prytz, Øystein, Meijerink, Andries, and Nilsen, Ola

Abstract

Luminescent materials enable warm white LEDs, molecular tagging, enhanced optoelectronics and can improve energy harvesting. With the recent development of multi-step processes like down- and upconversion and the difficulty in sensitizing these, it is clear that optimizing all properties simultaneously is not possible within a single material class. In this work, we have utilized the layer-by-layer approach of atomic layer deposition to combine broad absorption from an aromatic molecule with the high emission yields of crystalline multi-layer lanthanide fluorides in a single-step nanocomposite process. This approach results in complete energy transfer from the organic molecule while providing inorganic fluoride-like lanthanide luminescence. Sm3+ is easily quenched by organic sensitizers, but in our case we obtain strong fluoride-like Sm3+ emission sensitized by strong UV absorption of terephthalic acid. This design allows combinations of otherwise incompatible species, both with respect to normally incompatible synthesis requirements and in controlling energy transfer and quenching routes.

Published
2020

38. Single-step approach to sensitized luminescence through bulk-embedded organics in crystalline fluorides

Author

Sub Condensed Matter and Interfaces, Condensed Matter and Interfaces, Hansen, Per Anders, Zikmund, Tomas, Yu, Ting, Kvalvik, Julie Nitsche, Aarholt, Thomas, Prytz, Øystein, Meijerink, Andries, Nilsen, Ola, Sub Condensed Matter and Interfaces, Condensed Matter and Interfaces, Hansen, Per Anders, Zikmund, Tomas, Yu, Ting, Kvalvik, Julie Nitsche, Aarholt, Thomas, Prytz, Øystein, Meijerink, Andries, and Nilsen, Ola

Published
2020

39. Solar-driven plasmonic heterostructure Ti/TiO2-x with gradient doping for sustainable plasmon-enhanced catalysis

Author

Cheng, Chaoqun, Akram, Muhammad Nadeem, Nilsen, Ola, Pryds, Nini, Wang, Kaiying, Cheng, Chaoqun, Akram, Muhammad Nadeem, Nilsen, Ola, Pryds, Nini, and Wang, Kaiying

Abstract

Plasmon-enhanced harvesting of photons has contributed to the photochemical conversion and storage of solar energy. However, high dependence on noble metals and weak coupling in heterostructures constrain the progress towards sustainable plasmonic enhancement. Here earth-abundant Ti is studied to achieve the plasmonic enhancement of catalytic activity in a solar-driven heterostructure Ti/TiO2-x. The heterostructure was fabricated by engineering an intense coupling of a surface-etched Ti metal and a gradient-based TiO2-x dielectric via diffusion doping. Ti/TiO2-x exhibits a highly resonant light absorption band associated with surface plasmon resonances that exhibit strong near-field enhancement (NFE) and hot electron injection effects. In a photoelectrochemical system, intense interaction of the resonant plasmons with a vicinal TiO2-x dielectric accelerates the transfer of solar energy to charge carriers for plasmon-enhanced water splitting reactions. Moreover, the plasmonic Ti/TiO2-x structure presents sustained enhanced redox activities over 100 h. The intense coupling by gradient doping offers an effective approach to enable the plasmon resonances of Ti excited by visible light. The Ti-based plasmonic heterostructure potentially opens an alternative avenue towards sustainable plasmon-enhanced catalysis.

Published
2020

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