Details
| Original language | English |
|---|---|
| Article number | 159746 |
| Journal | Journal of Alloys and Compounds |
| Volume | 872 |
| Early online date | 2 Apr 2021 |
| Publication status | Published - 15 Aug 2021 |
Abstract
Photoinduced hydrophilic behavior of TiO2 thin film synthesized by atomic layer deposition method on p-Si wafer as well on SiO2-coated glass has been studied. In contrast to the TiO2 film on SiO2-coated glass, the TiO2 film on the Si wafer initially had a moderate hydrophobicity and became more hydrophobic upon visible light exposure. Such a significant difference was explained by the formation of a type-II TiO2–Si heterostructure that was confirmed by the alteration of the work function. The role of photoelectrons in the mechanism of light-induced hydrophilic conversion of the TiO2 surface was elucidated, which reduces to the deactivation of both active surface sites responsible for the superhydrophilic transition and already existing hydrophilic sites. Reversible hydrophilic-to-hydrophobic surface conversion upon switching UV exposure by visible light has been demonstrated for TiO2/Si coatings. Similar to the tensiometric data, a cyclic change in the work function value was found. The observed cycles in values of water contact angle and work function were gradually ceasing. This phenomenon was associated with the formation of the interfacial SiOx layer as a result of light-induced passivation of silicon at the TiO2–Si interface.
Keywords
- Photoinduced superhydrophilicity, Silicon, Substrate, Thin film, TiO-Si, Titanium dioxide, Type-II heterostructure
ASJC Scopus subject areas
- Engineering(all)
- Mechanics of Materials
- Engineering(all)
- Mechanical Engineering
- Materials Science(all)
- Metals and Alloys
- Materials Science(all)
- Materials Chemistry
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In: Journal of Alloys and Compounds, Vol. 872, 159746, 15.08.2021.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Photoinduced hydrophilic behavior of TiO2 thin film on Si substrate
AU - Rudakova, Aida V.
AU - Emeline, Alexei V.
AU - Romanychev, Andrey I.
AU - Bahnemann, Detlef W.
N1 - Funding Information: The present study was performed within the Project ‘‘Establishment of the Laboratory ‘‘Photoactive Nanocomposite Materials” supported by a Research Grant of the Saint-Petersburg State University (Pure ID 73032813 ). A.V. Rudakova thanks to the Russian Foundation for Basic Research grant (No. 18-03-00855 ) which supported the studies of photoinduced hydrophilicity of composite thin films. Authors are also grateful to the RC “Nanophotonics”, RC “Centre for Innovative Technologies of Composite Nanomaterials” (personally to Denis G. Fuks) RC “Nanotechnology”, RC “X-ray Diffraction Studies” (personally to Dr. Igor Kasatkin), RC “Centre for Physical Methods of Surface Investigation” (personally to Dr. Alexandra Koroleva), RC “Centre for Optical and Laser Materials Research” of the Research Park at Saint-Petersburg State University for helpful assistance in conducting synthesis and characterization of the samples.
PY - 2021/8/15
Y1 - 2021/8/15
N2 - Photoinduced hydrophilic behavior of TiO2 thin film synthesized by atomic layer deposition method on p-Si wafer as well on SiO2-coated glass has been studied. In contrast to the TiO2 film on SiO2-coated glass, the TiO2 film on the Si wafer initially had a moderate hydrophobicity and became more hydrophobic upon visible light exposure. Such a significant difference was explained by the formation of a type-II TiO2–Si heterostructure that was confirmed by the alteration of the work function. The role of photoelectrons in the mechanism of light-induced hydrophilic conversion of the TiO2 surface was elucidated, which reduces to the deactivation of both active surface sites responsible for the superhydrophilic transition and already existing hydrophilic sites. Reversible hydrophilic-to-hydrophobic surface conversion upon switching UV exposure by visible light has been demonstrated for TiO2/Si coatings. Similar to the tensiometric data, a cyclic change in the work function value was found. The observed cycles in values of water contact angle and work function were gradually ceasing. This phenomenon was associated with the formation of the interfacial SiOx layer as a result of light-induced passivation of silicon at the TiO2–Si interface.
AB - Photoinduced hydrophilic behavior of TiO2 thin film synthesized by atomic layer deposition method on p-Si wafer as well on SiO2-coated glass has been studied. In contrast to the TiO2 film on SiO2-coated glass, the TiO2 film on the Si wafer initially had a moderate hydrophobicity and became more hydrophobic upon visible light exposure. Such a significant difference was explained by the formation of a type-II TiO2–Si heterostructure that was confirmed by the alteration of the work function. The role of photoelectrons in the mechanism of light-induced hydrophilic conversion of the TiO2 surface was elucidated, which reduces to the deactivation of both active surface sites responsible for the superhydrophilic transition and already existing hydrophilic sites. Reversible hydrophilic-to-hydrophobic surface conversion upon switching UV exposure by visible light has been demonstrated for TiO2/Si coatings. Similar to the tensiometric data, a cyclic change in the work function value was found. The observed cycles in values of water contact angle and work function were gradually ceasing. This phenomenon was associated with the formation of the interfacial SiOx layer as a result of light-induced passivation of silicon at the TiO2–Si interface.
KW - Photoinduced superhydrophilicity
KW - Silicon
KW - Substrate
KW - Thin film
KW - TiO-Si
KW - Titanium dioxide
KW - Type-II heterostructure
UR - http://www.scopus.com/inward/record.url?scp=85103791437&partnerID=8YFLogxK
U2 - 10.1016/j.jallcom.2021.159746
DO - 10.1016/j.jallcom.2021.159746
M3 - Article
AN - SCOPUS:85103791437
VL - 872
JO - Journal of Alloys and Compounds
JF - Journal of Alloys and Compounds
SN - 0925-8388
M1 - 159746
ER -