Functionalization of conducting oxides by ion beam and defect engineering (FUNCTION)

• Madathil, Reshma; Thoreton, Vincent; Prytz, Øystein & Norby, Truls Eivind (2023). On the high-temperature oxidation of ZnSb for thermoelectric applications. Corrosion Science. ISSN 0010-938X. 210. doi: 10.1016/j.corsci.2022.110826. Fulltekst i vitenarkiv
• Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; García Fernández, Javier; Haug, Kristian; Galeckas, Augustinas & Jensen, Ingvild Julie Thue [Vis alle 9 forfattere av denne artikkelen] (2023). Optical properties of ZnFe2O4 nanoparticles and Fe-decorated inversion domain boundaries in ZnO. Nanoscale Advances. 5(7), s. 2102–2110. doi: 10.1039/d2na00849a. Fulltekst i vitenarkiv Vis sammendrag

  The maximum efficiency of solar cells utilizing a single layer for photovoltaic conversion is given by the single junction Shockley–Queisser limit. In tandem solar cells, a stack of materials with different band gaps contribute to the conversion, enabling tandem cells to exceed the single junction Shockley–Queisser limit. An intriguing variant of this approach is to embed semiconducting nanoparticles in a transparent conducting oxide (TCO) solar cell front contact. This alternative route would enhance the functionality of the TCO layer, allowing it to participate directly in photovoltaic conversion via photon absorption and charge carrier generation in the nanoparticles. Here, we demonstrate the functionalization of ZnO through incorporation of either ZnFe2O4 spinel nanoparticles (NPs) or inversion domain boundaries (IDBs) decorated by Fe. Diffuse reflectance spectroscopy and electron energy loss spectroscopy show that samples containing spinel particles and samples containing IDBs decorated by Fe both display enhanced absorption in the visible range at around 2.0 and 2.6 eV. This striking functional similarity was attributed to the local structural similarity around Fe-ions in spinel ZnFe2O4 and at Fe-decorated basal IDBs. Hence, functional properties of the ZnFe2O4 arise already for the two-dimensional basal IDBs, from which these planar defects behave like two-dimensional spinel-like inclusions in ZnO. Cathodoluminescence spectra reveal an increased luminescence around the band edge of spinel ZnFe2O4 when measuring on the spinel ZnFe2O4 NPs embedded in ZnO, whereas spectra from Fe-decorated IDBs could be deconvoluted into luminescence contributions from bulk ZnO and bulk ZnFe2O4.

• Montag, S.; Splith, D.; Kneiß, M.; Grundmann, M.; Garcia Fernandez, Javier & Prytz, Øystein [Vis alle 7 forfattere av denne artikkelen] (2023). Cation segregation observed in an (In,Ga) 2 O3 material thin film library beyond the miscibility limit of the bixbyite structure. PHYSICAL REVIEW MATERIALS. ISSN 2475-9953. 7(9). doi: 10.1103/PhysRevMaterials.7.094603. Fulltekst i vitenarkiv
• Thøgersen, Annett; Jensen, Ingvild Julie Thue; Belle, Branson Delano; Stange, Marit Synnøve Sæverud; Reinertsen, Vilde Mari & Kjeldstad, Torunn [Vis alle 9 forfattere av denne artikkelen] (2022). Plasmonic properties of aluminium nanowires in amorphous silicon. Journal of Physics: Condensed Matter. ISSN 0953-8984. 35(6), s. 1–10. doi: 10.1088/1361-648X/aca30e. Fulltekst i vitenarkiv
• Both, Kevin Gregor; Reinertsen, Vilde Mari; Aarholt, Thomas; Jensen, Ingvild Julie Thue; Neagu, Dragos & Prytz, Øystein [Vis alle 8 forfattere av denne artikkelen] (2022). Ni-doped A-site excess SrTiO3 thin films modified with Au nanoparticles by a thermodynamically-driven restructuring for plasmonic activity. Catalysis Today. ISSN 0920-5861. 413. doi: 10.1016/j.cattod.2022.11.011. Fulltekst i vitenarkiv Vis sammendrag

  Plasmonically active nanoparticles offer a promising pathway to extend the absorption range of photocatalysts. While not necessarily catalytically active themselves, these particles allow the absorption of lower energy photons in wide band gap photocatalysts. Here, we present A-site excess SrTiO3 thin films, doped with Ni, where through a subsequent exsolution process we created well-socketed Ni nanoparticles in the surface of SrTiO3. These were galvanically replaced by Au, resulting in well-socketed Au nanoparticles with variable size on the surface, depending on the galvanic replacement time. Photoelectrochemical measurements and electron energy loss spectroscopy revealed the improved photoresponse of the thin films by plasmonic activity of the nanoparticles. The energy of the plasmon peak suggests that the main improvement results from the injection of hot charge carriers. Our study opens new avenues for the design and synthesis of the next generation of photocatalytic materials.

• Garcia Fernandez, Javier; Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Karlsen, Ole Bjørn; Vines, Lasse & Prytz, Øystein (2022). Formation of γ-Ga2O3 by ion implantation: Polymorphic phase transformation of β-Ga2O3. Applied Physics Letters. ISSN 0003-6951. 121(19). doi: 10.1063/5.0120103. Fulltekst i vitenarkiv
• Kjeldby, Snorre Braathen; Azarov, Alexander; Nguyen, Phuong Dan; Venkatachalapathy, Vishnukanthan; Mikšová, R. & MacKová, A. [Vis alle 9 forfattere av denne artikkelen] (2022). Radiation-induced defect accumulation and annealing in Si-implanted gallium oxide. Journal of Applied Physics. ISSN 0021-8979. 131(12). doi: 10.1063/5.0083858. Fulltekst i vitenarkiv
• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Galvanic Restructuring of Exsolved Nanoparticles for Plasmonic and Electrocatalytic Energy Conversion. Small. ISSN 1613-6810. 18(29). doi: 10.1002/smll.202201106. Fulltekst i vitenarkiv
• Aarseth, Bjørn Lupton; Granerød, Cecilie Skjold; Galeckas, Augustinas; Azarov, Alexander; Nguyen, Phuong Dan & Prytz, Øystein [Vis alle 7 forfattere av denne artikkelen] (2021). Formation and functionalization of Ge-nanoparticles in ZnO. Nanotechnology. ISSN 0957-4484. 32(50). doi: 10.1088/1361-6528/ac264a. Fulltekst i vitenarkiv
• Granerød, Cecilie Skjold; Aarseth, Bjørn Lupton; Nguyen, Phuong Dan; Bazioti, Kalliopi; Azarov, Alexander & Svensson, Bengt Gunnar [Vis alle 8 forfattere av denne artikkelen] (2019). Structural and optical properties of individual Zn2GeO4 particles embedded in ZnO. Nanotechnology. ISSN 0957-4484. 30(22), s. 1–6. doi: 10.1088/1361-6528/ab061c. Fulltekst i vitenarkiv

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• Garcia Fernandez, Javier; Kjeldby, Snorre Braathen; Azarov, Alexander; Pokle, Anuj; Nguyen, Phuong Dan & Vines, Lasse [Vis alle 8 forfattere av denne artikkelen] (2023). Polymorph engineering and radiation tolerance in β-Ga2O3.
• Garcia Fernandez, Javier; Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Haug, Kristian; Galeckas, Augustinas & Jensen, Ingvild Julie Thue [Vis alle 9 forfattere av denne artikkelen] (2023). Optical properties and structure relationship in ZnO:Fe with inversion domain boundaries and ZnFe2O4/ZnO heterostructures.
• Kjeldby, Snorre Braathen; García Fernández, Javier; Nguyen, Phuong Dan; Prytz, Øystein & Vines, Lasse (2023). Implantation for polymorphic transformation in Ga2O3: thermal evolution and luminescence. Vis sammendrag

  Dette foredraget presenterer ioneimplantasjonindusert fasetransformasjon i galliumoksid, Ga2O3, fra beta-fasen til gamma-fasen. Den siste tiden har det vært utbredt vitenskaplig interesse i denne transformasjonen, som, basert på tilgjengelige data, ser ut til å være uavhengig av det implanterte speciet. Utover å presentere forsøk som fastslår den termiske stabiliteten til gamma-fasen, opp til 500 eller 700 grader Celsius avhengig av implantasjonsparametre, presenterer vi her også de første luminesensmålingene på slike prøver med høy romlig oppløsning, hovedsaklig fra prøver implantert med germanium, med støttende resultater fra nikkelimplanterte prøver. Både intrinsisk luminesens, fra selvlokaliserte hull og intrinsiske defekter, og ekstrinsisk luminesens fra krom ble studert. Foredraget bidrar til å klargjøre ikke bare strukturen men også egenskapene til fasetransformerte lag i galliumoksid fra ioneimplantasjon.

• Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Garcia Fernandez, Javier; Haug, Kristian; Galeckas, Augustinas & Jensen, Ingvild Julie Thue [Vis alle 9 forfattere av denne artikkelen] (2022). Optical properties of Fe-decorated inversion domain boundaries and embedded spinel zinc ferrite nanoparticles in zinc oxide.
• Kjeldby, Snorre Braathen; Azarov, Alexander; Nguyen, Phuong Dan; Garcia Fernandez, Javier; Venkatachalapathy, Vishnukanthan & Mikšová, Romana [Vis alle 10 forfattere av denne artikkelen] (2022). Structure and luminescence properties of Si-implanted β-Ga2O3.
• Kjeldby, Snorre Braathen; Azarov, Alexander; Nguyen, Phuong Dan; Venkatachalapathy, Vishnukanthan; Mikšová, Romana & Macková, Anna [Vis alle 10 forfattere av denne artikkelen] (2022). Structural Transformation of β-Ga2O3 through Si-implantation.
• Garcia Fernandez, Javier; Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Haug, Kristian; Galeckas, Augustinas & Jensen, Ingvild Julie Thue [Vis alle 9 forfattere av denne artikkelen] (2022). Structural and optical investigation of Fe-ZnO nanoarchitectures: from inversion domain boundaries to ZnO/ZnFe2O4 heterostructure.
• Both, Kevin Gregor; Reinertsen, Vilde Mari; Kang, Xiaolan; Neagu, Dragos; Prytz, Øystein & Norby, Truls [Vis alle 7 forfattere av denne artikkelen] (2022). Thin Film Exsolution of Metal Nanoparticles and Their Galvanic Restructuring for Plasmonically Enhanced Photocatalytic Activity.
• Both, Kevin Gregor; Reinertsen, Vilde Mari; Kang, Xiaolan; Aarholt, Thomas; Neagu, Dragos & Prytz, Øystein [Vis alle 8 forfattere av denne artikkelen] (2022). Improved Photoelectrochemical Performance of SrTiO3 by Plasmonically Active Au Nanoparticles.
• Elgvin, Cana; Kjeldby, Snorre Braathen; Both, Kevin Gregor; Nguyen, Phuong Dan & Prytz, Øystein (2022). Optical Properties of Zinc Ferrite Nanoparticles Embedded in Zinc Oxide Thin Films Investigated by STEM, EELS and CL.
• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Galvanic restructuring of exsolved nanoparticles for plasmonic and electrocatalytic energy conversion .
• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Galvanic Restructuring of Exsolved Nanoparticles for Plasmonic and Electrocatalytic Energy Conversion (Small 29/2022 Inside back cover feature). Small. ISSN 1613-6810. 18(29).
• Aarholt, Thomas; Both, Kevin Gregor; Reinertsen, Vilde Mari & Prytz, Øystein (2021). Surface plasmon investigations by STEM-EELS mapping of Au/Ni nanoparticles on STO. Vis sammendrag

  Metallic nanoparticles have traditionally had sharp absorption peaks between 1 and 5 eV due to the excitation of surface plasmons. Localized surface plasmon resonance (LSPR) is the coherent oscillation of quasi-free electrons excited by the electromagnetic fields of a photon or fast electron1,2. Since the absorption peak energies are in the range of visible light, surface plasmons present a potential pathway for absorbing energy to drive photoelectrochemical reactions or contribute to photovoltaic applications. For driving photoelectrochemical reactions, one difficulty is placing photoactive nanoparticles near the catalyst responsible for a chosen reaction, for example, water splitting. The ideal semiconductor for water splitting has a bandgap of 1.9 – 2.3 eV, although semiconductors in this range are seldom stable during photocatalytic water splitting3. Utilizing plasmonics in wide bandgap semiconductors is a promising alternative, avoiding the stability issue3. In this work, we present a STEM-EELS study of Au nanoparticles created by galvanic replacement of Ni nanoparticles grown by exsolution of a PLD-deposited thin-film of A-site excess strontium titanate (Sr1.07Ti 0.93Ni0.07O 3-δ) (STO). STO is an indirect, wide bandgap (3.2 eV) perovskite, studied as a promising photocatalyst for water splitting 4. Ni can easily substitute the Ti in the STO, making it a suitable candidate for exsolution, while Au cannot substitute Ti5. Simultaneously, Ni nanoparticles barely show any plasmonic activities, while Au particles are second only to Ag nanoparticles6. The presented manufacturing technique results in nanoparticles of gold and nickel freestanding, but socketed, on the surface and embedded in the bulk, with diameters between 50 and 100 nm, which are well-suited for plasmonic applications. As a starting point, STEM-EELS was performed with a monochromated 300kV STEM probe with ZeroLoss Peak (ZLP) full-width at half-maximum of 110 meV on an FEI Titan G2. A peculiarly shaped gold nanocluster was studied. After removing the ZLP, the spectrum image was linearly fitted with Gaussians centered at 1.46, 1.95, and 2.40 eV. The 2.40 eV peak is a well-known Au surface plasmon, whereas the remaining two are investigated in conjunction with modeling approaches. An RGB composite of the fit results can be seen in figure 1. Spectra extracted from the coloured regions can be seen in figure 2.

• Kjeldby, Snorre Braathen; Azarov, Alexander; Aarholt, Thomas; Prytz, Øystein & Vines, Lasse (2021). Defect-annealing in Si+-implanted β-Ga2O3.
• Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Haug, Kristian; Galeckas, Augustinas; Jensen, Ingvild Julie Thue & Thøgersen, Annett [Vis alle 8 forfattere av denne artikkelen] (2021). EELS and SEM-CL investigations of ZnFe2O4 nanoparticles and iron-decorated inversion domain boundaries in bulk ZnO.
• Elgvin, Cana; Nguyen, Phuong Dan; Both, Kevin Gregor; Vines, Lasse & Prytz, Øystein (2021). Crystallographically oriented ZnFe2O4 nanoparticles in ZnO thin films .
• Nguyen, Phuong Dan; Granerød, Cecilie Skjold; Aarseth, Bjørn Lupton; Bazioti, Kalliopi; Azarov, Alexander & Svensson, Bengt Gunnar [Vis alle 8 forfattere av denne artikkelen] (2019). Structural and optical properties of individual Zn2GeO4 particles embedded in ZnO.
• Haug, Kristian; Nguyen, Phuong Dan; Karlsen, Ole Bjørn; Aarholt, Thomas; Bazioti, Kalliopi & Prytz, Øystein (2019). Zinc ferrite spinel embedded in ZnO matrix for solar applications.
• Bergli, Jørgen & Prytz, Øystein (2021). Solid state precipitation of spinels in zinc oxide - A microstructure study. Universitetet i Oslo.
• Elgvin, Cana & Prytz, Øystein (2021). Characterization and optical properties of ZnFe2O4 nanoparticles in ZnO thin films - A (S)TEM study. Universitetet i Oslo.
• Haug, Kristian & Prytz, Øystein (2019). Functionalization of transparent conducting oxides. Zinc ferrite spinel in ZnO. Universitetet i Oslo.

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