torunkj

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Academic interests

I am working on advanced materials for renewable energy. The materials are mostly semiconducting, and I am particular exploring how the properties change when the dimensions are reduced dramatically, all the way down to the nanoscale.

Background

I graduated from the University of Oslo in 2012 with a master in "Materials, Energy and Nanotechnology". During my master thesis I worked on thermoelectric oxides, more precisely La0,7Sr0,3CoO(3-delta) (0 < delta < 0,15), and I investigated how the nanostructure of the oxide affected the thermoelectrical properties.

After my studies I explored the "real world", and worked as a consultant for two years. I got to know a lot of exiting Norwegian companies within many different industries. Despite two very interesting years, I missed researching how and why things are the way they are. This led me back to the university, and I hope that my work will take us one step closer to cheaper and more efficient solar cells.

Teaching

Spring 2016: FYS3320 - Fysikk og energiressurser

Autumn 2016: ENERGI4010 - Sustainable energy resources

Autumn 2017: ENERGI4010 - Sustainable energy resources

Partners

My project, Nanosol is a collaboration between SINTEF Materials and Chemistry and the University of Oslo.

Tags: Atomic Layer Deposition, SMN, Semiconductors, Solar cells, LENS, Silicon

Roosloot, Nathan Abel; Lindholm, Dag; Adhikari, Sayan; Clayer, Francois; DeGasperi, Curtis L. & Denfeld, Blaize A. [Show all 18 contributors for this article] (2026). Comparison of humidity-induced stress levels between floating and ground-mounted photovoltaics. Solar Energy. ISSN 0038-092X. 316. doi: 10.1016/j.solener.2026.114923. Full text in Research Archive Show summary
Floating photovoltaic (FPV) modules operate above water, leading to concerns about increased humidity-induced degradation compared to ground-mounted PV (GPV) modules. However, data to assess FPV degradation are limited. This study addresses this knowledge gap by analysing multi-year meteorological datasets from seven inland water bodies and nearby locations on land and subsequently calculating module temperatures, relative humidities (RH), and moisture ingress profiles. Ambient and module temperatures over water and land were similar (absolute mean differences of under 2 °C), while RHs over water surfaces could be higher or lower than over land (absolute mean differences of up to 9 percentage points), depending on location. Over land, diurnal fluctuations in temperature and RH were higher than over water, attributed to the stabilizing influence of water bodies. Modelled internal moisture contents were almost always higher in GPV modules than in FPV ones (up to 37% higher mean concentration). Lastly, the effects of FPV system design on humidity-induced stress were studied by varying module height above water and system heat transfer efficiency. This led to changes in internal moisture contents (up to 47% and 42% differences in mean moisture concentration, respectively) that often exceeded the observed water-land differences, indicating the importance of FPV system design on humidity-induced stress. This study challenges the commonly held assumption of universally greater humidity-induced stress in FPV systems and highlights the critical role of site-specific factors and system design, thereby advancing the understanding of FPV reliability.
Nysted, Vilde Stueland; Kjeldstad, Torunn; Lindholm, Dag; Ulset, Marit Sandsaunet & Selj, Josefine Helene Krogh (2025). Impact of Wind Speed and Direction on Cooling of a Pontoon-Based Floating Photovoltaic System. IEEE Journal of Photovoltaics. ISSN 2156-3381. 15(6), p. 955–964. doi: 10.1109/jphotov.2025.3611425. Full text in Research Archive
Nysted, Vilde Stueland; Stieng, Lars Einar Sørensen; Kumar, Manish; Roosloot, Nathan Abel; Otnes, Gaute & Kjeldstad, Torunn [Show all 7 contributors for this article] (2025). Modelling wave-induced losses for floating photovoltaics: Impact of design parameters and environmental conditions. Solar Energy. ISSN 0038-092X. 293. doi: 10.1016/j.solener.2025.113439. Full text in Research Archive Show summary
The interest in floating photovoltaics (FPV) as a land-sparing alternative has been rapidly growing over the last few years. So far, most of the installed FPV systems are inland on relatively calm waters. However, with the expanding market, FPV is moving to nearshore and offshore locations. There, larger waves can be expected resulting in a need for evaluating the impact of wave motion on the performance of FPV systems. Wave-induced movements of the PV panels can lead to varying irradiance levels, also within the string of panels, causing wave-induced loss (WIL). In this work, we have developed a model to simulate WIL for FPV systems. The model consists of three main modelling steps, wave-structure-interaction modelling, irradiance modelling and electrical modelling, where the second step has been experimentally verified. In the model, the in-house software 3DFloat is used to simulate the movement of the PV panels, and existing python libraries are used for the irradiance and electrical modelling. With this method, WIL has been simulated for different scenarios, to study the influence of different locations, sea states, times of year, string lengths, tilt angles and wave directions. The simulated WIL varied greatly with the chosen conditions. As an example, the WIL ranged from 3.3% for a significant wave height of 0.25 m to 6.7% for a significant wave height of 1 m.
Nysted, Vilde Stueland; Lindholm, Dag; Selj, Josefine & Kjeldstad, Torunn (2024). Floating photovoltaics: modelled and experimental operating temperatures and the impact of wind speed and direction. EPJ Photovoltaics. 15. doi: 10.1051/epjpv/2024020. Full text in Research Archive Show summary
Floating photovoltaics (FPV) is rapidly emerging as a promising alternative to ground-mounted PV (GPV) where available land area is scarce or expensive. Improved cooling has often been reported as a benefit of FPV, as cell temperature is an important parameter for the performance of a PV system. However, more recent literature shows that the cooling effect depends strongly on FPV technology and that it is not always superior to that of open rack GPV systems. There is still a need for more information on how to estimate cell temperatures for FPV systems, and how to consider the influence of various environmental factors such as wind speed and direction. Operating cell temperature may be estimated with the PVsyst model, where heat loss coefficients (U-values) denote the heat transfer capabilities of the PV system. In this work, cell temperatures and U-values for a small footprint FPV system with east-west orientation and a 15° tilt located in Sri Lanka are studied using both module temperature measurements and computational fluid dynamics (CFD) modelling. CFD modelling allows for investigating the influence of both wind speed and direction on cell temperatures, as well as to look at the distribution of cell temperatures within the system under different wind conditions. Calculations based on measurements give Uc = 22.6 W/m2K and Uv = 4.9 Ws/m3K and correlate well with CFD calculations. We also show that wind direction, system configuration and sensor placement influence the estimated U-values, complicating the use of tabulated values for any given technology.
Dörenkämper, Maarten; Jong, Minne M. de; Kroon, Jan; Nysted, Vilde Stueland; Selj, Josefine & Kjeldstad, Torunn (2023). Modeled and Measured Operating Temperatures of Floating PV Modules: A Comparison. Energies. 16(20). doi: 10.3390/en16207153. Full text in Research Archive
Thøgersen, Annett; Jensen, Ingvild Julie Thue; Belle, Branson Delano; Stange, Marit Synnøve Sæverud; Reinertsen, Vilde Mari & Kjeldstad, Torunn [Show all 9 contributors for this article] (2022). Plasmonic properties of aluminium nanowires in amorphous silicon. Journal of Physics: Condensed Matter. ISSN 0953-8984. 35(6), p. 1–10. doi: 10.1088/1361-648X/aca30e. Full text in Research Archive Show summary
Plasmonic structures can help enhance optical activity in the ultraviolet (UV) region and therefore enhancing photocatalytic reactions and the detection of organic and biological species. Most plasmonic structures are composed of Ag or Au. However, producing structures small enough for optical activity in the UV region has proved difficult. In this study, we demonstrate that aluminium nanowires are an excellent alternative. We investigated the plasmonic properties of the Al nanowires as well as the optoelectronic properties of the surrounding a − Si matrix by combining scanning transmission electron microscopy imaging, electron energy loss spectroscopy and electrodynamic modelling. We have found that the Al nanowires have distinct plasmonic modes in the UV and far UV region, from 0.75 eV to 13 eV. In addition, simulated results found that the size and spacing of the Al nanowires, as well as the embedding material were shown to have a large impact on the type of surface plasmon energies that can be generated in the material. Using electromagnetic modelling, we have identified the modes and illustrated how they could be tuned further.
Lindholm, Dag; Selj, Josefine Helene Krogh; Kjeldstad, Torunn; Fjær, Hallvard Gustav & Nysted, Vilde Stueland (2022). CFD modelling to derive U-values for floating PV technologies with large water footprint. Solar Energy. ISSN 0038-092X. 238, p. 238–247. doi: 10.1016/j.solener.2022.04.028. Full text in Research Archive
Kjeldstad, Torunn; Nysted, Vilde Stueland; Kumar, Manish; Oliviera-Pinto, Sara; Otnes, Gaute & Lindholm, Dag [Show all 7 contributors for this article] (2022). The performance and amphibious operation potential of a new floating photovoltaic technology. Solar Energy. ISSN 0038-092X. 239, p. 242–251. doi: 10.1016/j.solener.2022.04.065. Full text in Research Archive
Lindholm, Dag; Kjeldstad, Torunn; Selj, Josefine; Marstein, Erik Stensrud & Fjær, Hallvard Gustav (2021). Heat loss coefficients computed for floating PV modules. Progress in Photovoltaics. ISSN 1062-7995. 29(12), p. 1262–1273. doi: 10.1002/pip.3451. Full text in Research Archive
Kjeldstad, Torunn; Lindholm, Dag; Marstein, Erik & Selj, Josefine (2021). Cooling of floating photovoltaics and the importance of water temperature. Solar Energy. ISSN 0038-092X. 218, p. 544–551. doi: 10.1016/j.solener.2021.03.022. Full text in Research Archive
Kjeldstad, Torunn; Thøgersen, Annett; Stange, Marit Synnøve Sæverud; Jensen, Ingvild Julie Thue; Nilsen, Ola & Galeckas, Augustinas [Show all 7 contributors for this article] (2020). Selective etching of nanostructured a-Si:Al and its effect on porosity, Al gradient and surface oxidation. Thin Solid Films. ISSN 0040-6090. 702. doi: 10.1016/j.tsf.2020.137982. Full text in Research Archive Show summary
Nanoporous amorphous silicon (a-Si) with <5 nm cylindrical pores have been fabricated by phase separation of aluminum (Al) and silicon, forming self-assembled Al nanowires (NWs), followed by subsequent removal of Al by wet etching. This work studies the removal process of the Al NWs when using the different etchants HCl, H3PO4, and H2SO4. Total reflectance measurements are used in combination with theoretical modeling to estimate the lateral gradient of Al concentration formed during the etching process. X-ray Photoelectron Spectroscopy is used to show that the choice of Al etching agent has implications for the surface states of the remaining a-Si matrix. We have found that H3PO4 is the most efficient etching agent, while HCl provides a less oxidized a-Si matrix in addition to the least reflective surface. By varying the etching agent, the degree of surface oxidation and shape of Al gradient throughout the film can be tuned.
Kjeldstad, Torunn; Thøgersen, Annett; Stange, Marit Synnøve Sæverud; Azarov, Alexander; Monakhov, Eduard & Galeckas, Augustinas (2019). Monitoring selective etching of self-assembled nanostructured a-Si:Al films. Nanotechnology. ISSN 0957-4484. 30(13), p. 1–5. doi: 10.1088/1361-6528/aafb86. Full text in Research Archive Show summary
Nanoporous and nanowire structures based on silicon (Si) have a well recognized potential in a number of applications such as photovoltaics, energy storage and thermoelectricity. The immiscibility of Si and aluminum (Al) may be utilized to produce a thin film of vertically aligned Al nanowires of 5 nm diameter within an amorphous silicon matrix (a-Si), providing a cheap and scalable fabrication method for sub 5 nm size Si nanostructures. In this work we study functionalization of these structures by removal of the Al nanowires. The nanowires have been etched by an aqueous solution of HCl, which results in a structure of vertically aligned nanochannels in a-Si with admixture of SiO x . The removal of Al nanowires has been monitored by several electron microscopy techniques, x-ray diffraction, Rutherford backscattering spectroscopy, and optical reflectance. We have established that optical reflectance measurements can reliably identify the complete removal of Al, confirmed by other techniques. This provides a robust and relatively simple method for controlling the nano-fabrication process on a macroscopic scale.
Kjeldstad, Torunn; Thøgersen, Annett; Stange, Marit Synnøve Sæverud; Jensen, Ingvild Julie Thue; Monakhov, Eduard & Galeckas, Augustinas (2019). Surface effects and optical properties of self-assembled nanostructured a-Si:Al. Nanomaterials. 9(8), p. 1–12. doi: 10.3390/nano9081106. Full text in Research Archive Show summary
We present a study of the surface effects and optical properties of the self-assembled nanostructures comprised of vertically aligned 5 nm-diameter Al nanowires embedded in an amorphous Si matrix (a-Si:Al). The controlled (partial) removal of Al nanowires in a selective etching process yielded nanoporous a-Si media with a variable effective surface area. Different spectroscopy techniques, such as X-ray photoelectron spectroscopy (XPS), UV-Vis spectrophotometry and photoluminescence (PL), have been combined to investigate the impact of such nanostructuring on optical absorption and emission properties. We also examine long-term exposure to air ambient and show that increasing level of surface oxidation determines the oxide defect-related nature of the dominant PL emission from the nanoporous structures. The role of bulk, nanosize and surface effects in optical properties has been separated and quantified, providing a better understanding of the potential of such nanoporous a-Si:Al structures for future device developments
Thøgersen, Annett; Jensen, Ingvild Julie Thue; Stange, Marit Synnøve Sæverud; Kjeldstad, Torunn; Martinez-Martinez, Diego & Løvvik, Ole Martin [Show all 8 contributors for this article] (2018). Formation of nanoporous Si upon self-organized growth of Al and Si nanostructures. Nanotechnology. ISSN 0957-4484. 29(31). doi: 10.1088/1361-6528/aac36a. Full text in Research Archive Show summary
Nanostructured materials offer unique electronic and optical properties compared to their bulk counterparts. The challenging part of the synthesis is to create a balance between the control of design, size limitations, up-scalability and contamination. In this work we show that self-organized Al nanowires in amorphous Si can be produced at room temperature by magnetron co-sputtering using two individual targets. Nanoporous Si, containing nanotunnels with dimensions within the quantum confinement regime, were then made by selective etching of Al. The material properties, film growth, and composition of the films were investigated for different compositions. In addition, the reflectance of the etched film has been measured.
Kjeldstad, Torunn; Thøgersen, Annett; Nilsen, Ola; Monakhov, Edouard & Galeckas, Augustinas (2017). Controllable template approach for ZnO nanowire growth. Physica Status Solidi (a) applications and materials science. ISSN 1862-6300. 214(2), p. 1–6. doi: 10.1002/pssa.201600480. Full text in Research Archive Show summary
Anodic aluminum oxide (AAO) is an optically transparent material with uniform hexagonal pores, which has widely been used as a template for nanowire growth. This study examines the potential of utilizing commercially available AAO to fabricate sub-10 nm ZnO nanowires by atomic layer deposition. The pore diameter of the AAO framework is reduced by controlled deposition of . Subsequently, ZnO is deposited and ZnO nanowires are obtained. The analysis of structural and optical properties shows that the nanowires are polycrystalline, and exhibit a pronounced near band edge emission. Photoluminescence (PL) measurements are performed to monitor the effect of additional coating with and ZnO, on the optical stability of the AAO. The measurements indicate that the PL is highly influenced by the adsorption and desorption of species from the ambient at the surface. ALD deposition of a thin layer reduces considerably the effect of ambient atmosphere. The layer of facilitates PL characterization of very thin ZnO nanowires.

View all works in NVA

Riise, Heine Nygard; Honningdalsnes, Erlend Hustad; Kjeldstad, Torunn & Rizzi, Jonathan (2026). Hvordan kan vi produsere mer fornybar energi uten å bygge ned matjord eller natur?. Full text in Research Archive
Kjeldstad, Torunn (2026). New frontiers for solar PV: From fields to water. Full text in Research Archive
Wiig, Marie Syre; Nygård, Magnus Moe; Sødahl, Elin Dypvik & Kjeldstad, Torunn (2026). Accurate temperature modelling in energy yield assessments for large scale tracker systems. Full text in Research Archive
Wiig, Marie Syre; Nygård, Magnus Moe; Sødahl, Elin Dypvik & Kjeldstad, Torunn (2026). Understanding Energy-Yield Bias in Bifacial PV: Lessons from a 300 MWp Utility-Scale Plant. Full text in Research Archive
Riise, Heine Nygard; Kjeldstad, Torunn; Honningdalsnes, Erlend Hustad; Simensen, Trond & Mehlhoop, Anne Catriona (2025). Solkraft på grå arealer. Full text in Research Archive
Kjeldstad, Torunn (2025). Konsekvenser av solkraftanlegg for natur og miljø. Full text in Research Archive
Kjeldstad, Torunn; Sødahl, Elin Dypvik; Ulset, Marit Sandsaunet; Otnes, Gaute & Selj, Josefine Helene Krogh (2025). Degradation in floating PV: effects of low operating temperature. Full text in Research Archive
Øverås, Aslak & Kjeldstad, Torunn (2025). Fornybaren Podcast - Sol vokser rask globalt, men Norge henger etter. doi: https:/www.fornybarnorge.no/fornybaren/?gad_source=1&gad_campaignid=10262923139&gclid=CjwKCAiAoNbIBhB5EiwAZFbYGLhxXVRGuZnNpVRYW_kFO9B5f-mgJtSsb2p-rt51Fn4UQbIXpRlOBRoCGN0QAvD_BwE. Full text in Research Archive
Kjeldstad, Torunn; Inderberg, Tor Håkon Jackson; Hagen, Dagmar; Buvik, Magnus & Martinsen, Dina Christensen (2025). Bakkemontert solkraft i Norge: Hvorfor går det så sakte? Full text in Research Archive
Riise, Heine Nygard; Kjeldstad, Torunn & Honningdalsnes, Erlend Hustad (2025). Solceller på bakken kan gi mye strøm, men hva gjør det med naturen? [Internet]. forskning.no. Full text in Research Archive
Honningdalsnes, Erlend Hustad; Riise, Heine Nygard; Kjeldstad, Torunn; Marstein, Erik Stensrud; Stokkan, Gaute & Randle-Boggis, Richard [Show all 10 contributors for this article] (2024). Fordeler med solkraftverk på jord- og skogbruksarealer. Bondebladet. ISSN 0332-8414. Full text in Research Archive
Kjeldstad, Torunn; Riise, Heine Nygard; Hagen, Dagmar & Rizzi, Jonathan (2024). Slik kan solkraft-utbyggerne lære av konfliktene med vindkraft på land. Full text in Research Archive
Riise, Heine Nygard; Honningdalsnes, Erlend Hustad; Hagen, Dagmar; Sydenham, Markus A. K.; Mehlhoop, Anne Catriona & Simensen, Trond Aalvik [Show all 8 contributors for this article] (2024). Envisol – Presenting a Cross-Disciplinary Project on How PV Power Plants Influence Nature. Full text in Research Archive
Rønneberg, Sigrid; Kjeldstad, Torunn; Riise, Heine Nygard; Breen, Anneline Malling & Tollisen, Stian (2024). Alle nye bygg bør få integrerte solceller i bygningskroppen. Full text in Research Archive
Riise, Heine Nygard & Kjeldstad, Torunn (2024). Hvor mye sol har vi i Norge og hva gir det i kWh? Full text in Research Archive
Kjeldstad, Torunn (2024). Abels Tårn. [Radio]. NRK P2. Full text in Research Archive
Kjeldstad, Torunn; Selj, Josefine Helene Krogh & Nysted, Vilde Stueland (2024). Yield Assesment of FPV Systems. Full text in Research Archive
Jemterud, Torkild; Delsett, Lene Liebe; Hessen, Dag Olav & Kjeldstad, Torunn (2024). Abels tårn 24. mai 2024. [Radio]. NRK P2. Full text in Research Archive
Riise, Heine Nygard & Kjeldstad, Torunn (2024). SOLKRAFT PÅ GRÅ AREALER. Full text in Research Archive
Roosloot, Nathan Abel; Clayer, Francois; Lindholm, Dag; DeGasperi, Curtis; Desai, Ankur R. & Hornbach, Daniel [Show all 18 contributors for this article] (2024). Quantification of differences in humidity stress profiles between floating photovoltaics and ground mounted photovoltaics. Full text in Research Archive
Roosloot, Nathan Abel; Clayer, Francois; Lindholm, Dag; DeGasperi, Curtis; Desai, Ankur R. & Hornbach, Daniel [Show all 18 contributors for this article] (2024). Comparing humidity-induced stress levels between floating and ground-mounted PV. Full text in Research Archive
Kjeldstad, Torunn; Selj, Josefine Helene Krogh; Otnes, Gaute; Roosloot, Nathan Abel; Nysted, Vilde Stueland & Marstein, Erik Stensrud [Show all 8 contributors for this article] (2023). Quantifying module level stressors in floating PV systems. Full text in Research Archive
Kjeldstad, Torunn (2023). NFR 30års feiring - innslag om solkraft. Full text in Research Archive
Fjær, Hallvard Gustav; Nysted, Vilde Stueland; Roosloot, Nathan Abel; Lindholm, Dag; Kjeldstad, Torunn & Selj, Josefine Helene Krogh (2023). Stresses induced by personnel stepping on PV modules mounted on a floating elastic membrane. Full text in Research Archive
Ulset, Marit Sandsaunet; Kjeldstad, Torunn; Nysted, Vilde Stueland; Lindholm, Dag & Selj, Josefine Helene Krogh (2023). Thermal losses for floating PV - Wind direction dependencies. Full text in Research Archive
Nysted, Vilde Stueland; Kjeldstad, Torunn; Stieng, Lars Einar Sørensen; Otnes, Gaute & Selj, Josefine Helene Krogh (2023). Assessing the influence of wave motion on the performance of floating photovoltaic systems. Full text in Research Archive
Nysted, Vilde Stueland; Kjeldstad, Torunn; Lindholm, Dag & Balciunaite, Rugile (2022). Investigation of module temperatures for a floating photovoltaic system. Full text in Research Archive
Otnes, Gaute; Roosloot, Nathan; Kjeldstad, Torunn; Seiffert, Christoph & Selj, Josefine Helene Krogh (2022). Adapted stress testing for floating PV. Full text in Research Archive
Kumar, Manish; Nysted, Vilde Stueland; Otnes, Gaute; Kjeldstad, Torunn; Roosloot, Nathan & Selj, Josefine Helene Krogh (2022). Impact of Water Waves on the Output Power of Floating PV Systems on Water Bodies. Full text in Research Archive
Lindholm, Dag; Nysted, Vilde Stueland; Selj, Josefine Helene Krogh & Kjeldstad, Torunn (2022). Thermal losses for floating PV - Energy yield assessment. Full text in Research Archive
Kjeldstad, Torunn; Nysted, Vilde Stueland; Balciunaite, Rugile; Lindholm, Dag & Selj, Josefine Helene Krogh (2022). Floating solar technology in a tropical climate. Full text in Research Archive
Kjeldstad, Torunn (2022). Fra flytende påstander til konkret kunnskap. Full text in Research Archive
Kjeldstad, Torunn & Torkild, Jemterud (2022). Abels Tårn. [Radio]. NRK P2. Full text in Research Archive
Kjeldstad, Torunn (2021). Flytende solkraft- Et nytt norsk eventyr? Full text in Research Archive
Kjeldstad, Torunn (2021). Flytende solkraft. [Radio]. Abels tårn P1. Full text in Research Archive
Kjeldstad, Torunn; Otnes, Gaute; Pinto, sara; Lindholm, Dag & Selj, Josefine (2021). Performance and amphibious operation of a small-footprint FVP system from Current Solar. Full text in Research Archive
Kjeldstad, Torunn (2021). Er flytende solkraft den nye vin(d)en? [Radio]. Energinorge. Full text in Research Archive
Kjeldstad, Torunn (2019). Solar power – moving forward. Full text in Research Archive
Kjeldstad, Torunn (2019). Abels Tårn. [Radio]. NRK P2. Full text in Research Archive
Kjeldstad, Torunn (2019). Abels Tårn. [Radio]. NRK P2. Full text in Research Archive
Kjeldstad, Torunn (2019). Forskernatt - Forskernes eget talkshow. Full text in Research Archive
Kjeldstad, Torunn (2019). Science slam - Dikt om min forskning. Full text in Research Archive
Kjeldstad, Torunn (2019). En fornybar fremtid med solenergi – muligheter og utfordringer. Full text in Research Archive
Jemterud, Torkild; Kjeldstad, Torunn; Antonsen, Roger & Bøckman, Petter (2019). Abels tårn. [Radio]. Ekko, NRK P2. Full text in Research Archive
Delsett, Lene Liebe; Einevoll, Gaute; Kjeldstad, Torunn & Jemterud, Torkild (2018). Abels tårn 26. januar 2018. [Radio]. NRK P2 Ekko. Full text in Research Archive
Kjeldstad, Torunn (2018). Abels Tårn. [Radio]. NRK P2. Full text in Research Archive
Kjeldstad, Torunn; Thøgersen, Annett; Galeckas, Augustinas; Monakhov, Eduard; Stange, Marit Synnøve Sæverud & Nilsen, Ola (2018). Aluminum nanowires in amorphous silicon. Full text in Research Archive
Kjeldstad, Torunn (2018). Abels Tårn. [Radio]. NRK P2. Full text in Research Archive
Kjeldstad, Torunn (2018). Abels Tårn. [Radio]. NRK P2. Full text in Research Archive
Thøgersen, Annett; Kjeldstad, Torunn; Jensen, Ingvild Julie Thue; Muntingh, Agnar Georg Peder; Stange, Marit Synnøve Sæverud & Ulyashin, Alexander [Show all 9 contributors for this article] (2017). Plasmonic properties of aluminium nanowires in amorphous silicon and inverted silicon nanowires. Full text in Research Archive
Riise, Heine Nygard; Kjeldstad, Torunn; Sky, Thomas Neset & Borgersen, Jon Arthur (2017). MiNaLab-besøk frå Kongsskogen VGS. Full text in Research Archive
Riise, Heine Nygard; Aarseth, Bjørn Brevig; Kjeldstad, Torunn; Borgersen, Jon Arthur & Olsen, Vegard Skiftestad (2017). Besøk frå deltakarar i Fysikk-OL. Full text in Research Archive
Thøgersen, Annett; Kjeldstad, Torunn; Jensen, Ingvild Julie Thue; Stange, Marit Synnøve Sæverud; Ulyashin, Alexander & Galeckas, Augustinas [Show all 9 contributors for this article] (2017). Growing and characterizing self-organizing aluminium nanowires in amorphous silicon. Full text in Research Archive
Kjeldstad, Torunn (2017). Når noe veldig lite kan bli til noe stort. Full text in Research Archive
Kjeldstad, Torunn (2017). Når noe veldig lite kan bli til noe stort. Full text in Research Archive
Kjeldstad, Torunn; Thøgersen, Annett; Monakhov, Edouard & Galeckas, Augustinas (2017). Aluminium nanoparticles embedded in mesoporous aSi:H. Full text in Research Archive
Kjeldstad, Torunn (2017). Solceller. Full text in Research Archive
Kjeldstad, Torunn; Thøgersen, Annett; Stange, Marit Synnøve Sæverud; Galeckas, Augustinas & Monakhov, Edouard (2017). Self-assembled aluminium nanowires in silicon. Full text in Research Archive
Kjeldstad, Torunn (2017). Abels tårn. [Radio]. P2. Full text in Research Archive
Kjeldstad, Torunn; Galeckas, Augustinas; Nilsen, Ola; Azarov, Alexander; Stange, Marit Synnøve Sæverud & Diplas, Spyridon [Show all 7 contributors for this article] (2017). Self-assembly of Al-nanowires in silicon. Full text in Research Archive
Kjeldstad, Torunn; Thøgersen, Annett; Monakhov, Edouard & Galeckas, Augustinas (2017). Investigation of mesoporous aSi:H with embedded aluminium nanoparticles. Full text in Research Archive
Haraldsen, Kirsten Borse; Rogne, Sissel; Eskeland, Ragnhild; Kjeldstad, Torunn; Olsbye, Unni & Røyne, Anja (2017). Panelsamtale: Hva nå? DAMER! 100 år med kvinner i realfagene ved UiO. Full text in Research Archive Show summary
Innledning/forberedelser til panelsamtale ledet av Sissel Rogne under åpningen av utstillingen "Damer!"
Kjeldstad, Torunn; Galeckas, Augustinas; Nilsen, Ola; Azarov, Alexander; Stange, Marit Synnøve Sæverud & Diplas, Spyridon [Show all 7 contributors for this article] (2016). A new silicon nanostructure. Full text in Research Archive
Kjeldstad, Torunn; Galeckas, Augustinas; Monakhov, Edouard; Nilsen, Ola & Thøgersen, Annett (2016). Controllable template approach for ZnO nanowire growth. Full text in Research Archive
Kjeldstad, Torunn (2020). Characterization and functionalization of self-assembled nanostructures. Universitetet i Oslo. Full text in Research Archive Show summary
This thesis presents a study of the nanostructured a-Si:Al consisting of aluminum nanowires with < 5 nm diameter surrounded by amorphous Si. The nanostructure is formed by self-assembly of the nanowires during co-sputtering of silicon and aluminium. The motivation of the work lies in the material properties that can arise when approaching this scale, which makes this material interesting for a broad range of applications. In the last decades, a large research effort has been made towards Si nanostructures and other nanomaterials to develop cheaper and more efficient solutions towards photovoltaic devices and use of silicon in optoelectronic applications. Also, materials consisting of vertically aligned pores with a narrow diameter, as can be achieved by removing the Al NWs from the nanostructured a-Si:Al, can serve as a template for nanowire fabrication useful for a many different applications. The nanostructured a-Si:Al has previously received little attention, and a large number of questions related to fabrication parameters and material properties are unanswered. In this work, we try to unravel some of the material properties and bring more understanding of how the material can move closer to future applications. As removal of the aluminum nanowires is an important step towards these applications, much focus has been on this. By combining the detailed knowledge on the nanoscale available through transmission electron microscopy with simpler, more macroscopic techniques such as UV-Vis spectroscopy, we have shown that the removal process can be monitored by measuring reflectance. Not only may the nanowires be removed by selective etching using acids such as HCl, diluted H2SO4, and H3PO4, but the time it takes and the development on reflectance during etching can provide information on the quality of the wires and the aluminum gradient throughout the film. We hope that these results will aid other researchers in reproducing this unique nanostructured material, as it allows for process control on the nanoscale without the need for characterization by advanced electron microscopy. By combining a variety of characterization methods such as X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and ellipsometric porosimetry we have found that removal of the aluminum nanowires results in a partly oxidized nanoporous a-Si with porosity of 20 - 25 % and peak emission centring at 1.6 eV. Storage in air increases the level of oxidation and changes the emission characteristics. Therefore, a necessary step towards device fabrications may be to coat the nanoporous a-Si with a protective layer. The applicability of atomic layer deposition as a method for this has been proved promising from our experiments on its coating capabilities on narrow diameter anodic alumina.

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Published Apr. 22, 2015 8:24 AM - Last modified Dec. 5, 2017 3:14 PM