Eirini Zacharaki

• Kjeldby, Snorre Braathen; Nielsen, Dina Marie; Cooil, Simon Phillip; Frodason, Ymir Kalmann; Zacharaki, Eirini & Lee, In Hwan [Vis alle 10 forfattere av denne artikkelen] (2025). Tuning Properties of II-IV-Nitrides for Optoelectronic Applications. Advanced Optical Materials. 13(36). doi: 10.1002/adom.202502634. Fulltekst i vitenarkiv Vis sammendrag

  The earth-abundant II-IV-nitrides ZnSnN2 and ZnGeN2 are direct bandgap semiconductors with a wurtzite-derived crystal structure. Their alloys, ZnSnxGe1 − xN2, have bandgaps tunable across the full visible spectrum, making them interesting for many optoelectronic applications. Here, electrical, structural, and optical properties of near-stoichiometric ZnSnxGe1 − xN2 alloys, i.e., where [Zn]/([Zn]+[Ge]+[Sn]) ≈ 0.5, are reported, for samples synthesized by reactive magnetron sputtering. These results reveal unprecedentedly high electrical mobilities in Ge-rich alloys, with values of 136 and 400 cm2/Vs at room-temperature and ≈100 K, respectively. The bandgaps are determined from optical absorption measurements combined with hybrid density functional calculations and reveal a significant Burstein–Moss shift in the Sn rich alloys. Finally, band alignments are determined in the sputter-grown thin films by combining optical transmission measurements, hybrid density functional calculations, and UV photoelectron spectroscopy measurements, where the bandgap variation is predominantly caused by a shift of the conduction band edge. This work elucidates in unprecedented detail the tuning of optical and electrical properties in ZnSnxGe1 − xN2 by variation of the chemical composition, where bandgap values of alloys with x ∈ [0.5−0.7] are suitable for top cell absorbers in two-terminal tandem solar cells assuming a Si bottom cell.

• Zacharaki, Eirini; Bremmer, Marien G.; Vajeeston, Ponniah; Kalyva, Maria Evangelou; Fjellvåg, Helmer & Kooyman, Patricia J. [Vis alle 7 forfattere av denne artikkelen] (2020). One-pot synthesis of cobalt-rhenium nanoparticles taking the unusual beta-Mn type structure. Nanoscale Advances. 2, s. 1850–1853. doi: 10.1039/d0na00097c. Fulltekst i vitenarkiv Vis sammendrag

  Using a facile one-pot colloidal method, it is now possible to obtain monodisperse Co1−xRex nanoparticles (NPs), with excellent control of Re stoichiometry for x < 0.15. Re-incorporation in terms of a solid solution stabilizes the β-Mn polymorph relative to the hcp/ccp variants of cobalt. The NPs are thermally stable up to 300 °C, which may make them attractive as model catalysts.

• Slawinski, Wojciech Andrzej; Zacharaki, Eirini; Fjellvåg, Helmer & Sjåstad, Anja Olafsen (2018). Structural Arrangement in Close-Packed Cobalt Polytypes. Crystal Growth & Design. ISSN 1528-7483. 18(4), s. 2316–2325. doi: 10.1021/acs.cgd.7b01736. Fulltekst i vitenarkiv
• Zacharaki, Eirini; Beato, Pablo; Tiruvalam, Ramchandra R; Andersson, Klas J.; Fjellvåg, Helmer & Sjåstad, Anja Olafsen (2017). From Colloidal Monodisperse Nickel Nanoparticles to Well-Defined Ni/Al2O3 Model Catalysts. Langmuir. ISSN 0743-7463. 33(38), s. 9836–9843. doi: 10.1021/acs.langmuir.7b02197. Fulltekst i vitenarkiv Vis sammendrag

  In the past few decades, advances in colloidal nanoparticle synthesis have created new possibilities for the preparation of supported model catalysts. However, effective removal of surfactants is a prerequisite to evaluate the catalytic properties of these catalysts in any reaction of interest. Here we report on the colloidal preparation of surfactant-free Ni/Al2O3 model catalysts. Monodisperse Ni nanoparticles (NPs) with mean particle size ranging from 4 to 9 nm were synthesized via thermal decomposition of a zerovalent precursor in the presence of oleic acid. Five weight percent Ni/Al2O3 catalysts were produced by direct deposition of the presynthesized NPs on an alumina support, followed by thermal activation (oxidation–reduction cycle) for complete surfactant removal and surface cleaning. Structural and morphological characteristics of the nanoscale catalysts are described in detail following the propagation of the bulk and surface Ni species at the different treatment stages. Powder X-ray diffraction, electron microscopy, and temperature-programmed reduction experiments as well as infrared spectroscopy of CO adsorption and magnetic measurements were conducted. The applied thermal treatments are proven to be fully adequate for complete surfactant removal while preserving the metal particle size and the size distribution at the level attained by the colloidal synthesis. Compared with standard impregnated Ni/Al2O3 catalysts, the current model materials display narrowed Ni particle size distributions and increased reducibility with a higher fraction of the metallic nickel atoms exposed at the catalyst surface. © 2017 American Chemical Society

• Zacharaki, Eirini; Kalyva, Maria Evangelou; Fjellvåg, Helmer & Sjåstad, Anja Olafsen (2016). Burst nucleation by hot injection for size controlled synthesis of ε-cobalt nanoparticles. Chemistry Central Journal. 10(1). doi: 10.1186/s13065-016-0156-1. Fulltekst i vitenarkiv
• Bremmer, Marien G.; Zacharaki, Eirini; Sjåstad, Anja Olafsen; Navarro, Violeta; Frenken, Joost W. M. & Kooyman, Patricia J. (2016). In situ TEM observation of the Boudouard reaction: multi-layered graphene formation from CO on cobalt nanoparticles at atmospheric pressure. Faraday discussions. ISSN 1359-6640. 197, s. 337–351. doi: 10.1039/c6fd00185h. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Kjeldby, Snorre Braathen; Olsen, Vegard Skiftestad; Frodason, Ymir Kalmann; Zacharaki, Eirini; Cooil, Simon Phillip & Vines, Lasse [Vis alle 12 forfattere av denne artikkelen] (2025). Thin film top cell absorbers for multijunction solar cells. Fulltekst i vitenarkiv
• Sjåstad, Anja Olafsen; Zacharaki, Eirini; Bundli, Silje; Jensen, Martin; Kalyva, Maria Evangelou & Dhak, Prasanta [Vis alle 10 forfattere av denne artikkelen] (2017). Nanoparticles for heterogeneous catalysis of industrial relevant processes. Fulltekst i vitenarkiv
• Müller, Axel & Zacharaki, Eirini (2019). Mineralogical characterization of a mineral concentrate from the Niederschlag barite-fluorite deposit, Germany. Norges geologiske undersøkelse. Fulltekst i vitenarkiv
• Zacharaki, Eirini; Sjåstad, Anja Olafsen & Fjellvåg, Helmer (2018). Synthesis and Characterization of Colloidal Co, Co-Re and Ni Nanoparticles for Catalysis. Universitetet i Oslo. Fulltekst i vitenarkiv
• Muri, Marte Eiterstraum; Sjåstad, Anja Olafsen; Fjellvåg, Helmer & Zacharaki, Eirini (2016). Synthesis and characterization of free standing Pt-Rh nanoparticles, and 2 wt. % Pt 0.70 Rh 0.30 /Al2O3 and 20 wt. % Co1xRex/Al2O3 (0.00 ≤ x ≤ 0.15) metal-on-support catalysts. http://urn.nb.no/URN:NBN:no-48126. Fulltekst i vitenarkiv

Se alle arbeider i NVA