open access publication

Article, 2024

Understanding the light induced hydrophilicity of metal-oxide thin films

Nature Communications, ISSN 2041-1723, Volume 15, 1, Page 124, 10.1038/s41467-023-44603-2

Contributors

Deshpande, Rucha Anil 0000-0001-9158-036X [1] Navne, Jesper [1] Adelmark, Mathias Vadmand 0009-0002-5192-2171 [1] Shkondin, Evgeniy 0000-0002-8347-1814 [1] Crovetto, Andrea 0000-0003-1499-8740 [1] Hansen, Ole 0000-0002-6090-8323 [1] Bachmann, Julien 0000-0001-6480-6212 [1] [2] Taboryski, Rafael J 0000-0003-2491-1098 (Corresponding author) [1]

Affiliations

  1. [1] Technical University of Denmark
    2. [NORA names: DTU Technical University of Denmark; University; Denmark; Europe, EU; Nordic; OECD];
  2. [2] University of Erlangen-Nuremberg
    3. [NORA names: Germany; Europe, EU; OECD]

Abstract

Photocatalytic effects resulting in water splitting, reduction of carbon dioxide to fuels using solar energy, decomposition of organic compounds, and light-induced hydrophilicity observed on surfaces of various metal oxides (MOx), all rely on the same basic physical mechanisms, and have attracted considerable interest over the past decades. TiO2 and ZnO, two natively n-type doped wide bandgap semiconductors exhibit the effects mentioned above. In this study we propose a model for the photo-induced hydrophilicity in MOx films, and we test the model for TiO2/Si and ZnO/Si heterojunctions. Experimentally, we employ a wet exposure technique whereby the MOx surface is exposed to UV light while a water droplet is sitting on the surface, which allows for a continuous recording of contact angles during illumination. The proposed model and the experimental techniques allow a determination of minority carrier diffusion lengths by contact angle measurements and suggest design rules for materials exhibiting photocatalytic hydrophilicity. We expect that this methodology can be extended to improve our physical understanding of other photocatalytic surface effects.

Keywords

TiO2, TiO2/Si, UV light, ZnO, ZnO/Si, ZnO/Si heterojunction, angle, angle measurements, bandgap semiconductors, carbon dioxide, carrier diffusion length, compounds, contact, contact angle, contact angle measurements, continuous recording, decades, decomposition, decomposition of organic compounds, design, design rules, determination, diffusion length, dioxide, droplets, effect, energy, experimental techniques, exposure technique, films, fuel, heterojunction, hydrophilicity, illumination, length, light, light-induced hydrophilicity, materials, measurements, mechanism, metal, metal oxide thin films, metal oxides, methodology, minority carrier diffusion length, model, organic compounds, oxidation, photo-induced hydrophilicity, photocatalytic effect, physical mechanisms, physical understanding, records, reduction, reduction of carbon dioxide, rules, semiconductor, solar energy, splitting, study, surface, surface effects, technique, thin films, understanding, water, water droplets, water splitting, wide-bandgap semiconductors

Funders

  • The Velux Foundations

Data Provider: Digital Science

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