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Contact Angle Relaxation and Long-lasting Hydrophilicity of Sputtered Anatase TiO <sub/>2</sub> Thin Films by Novel Quantitative XPS Analysis
摘要： The contact angle relaxation of TiO2 surfaces is an important problem that must be understood, particularly for long-lasting hydrophilicity under dark conditions. The relaxation of sputtered anatase TiO2 thin films over a long time (~22 days) in an atmospheric environment was observed using quantitative XPS analysis. A new peak was identified as H2O within a donor-acceptor complex at ~2.57 eV above the lattice oxygen peak. This donor?acceptor complex turns out to be a key factor for long lasting hydrophilicity, and our model is presented. Adventitious carbon contamination was not the main cause of the contact angle relaxation. Instead, samples with lower amounts of donor?acceptor complexes (IDAC/Ibulk ≤ ~5%) underwent contact angle relaxation over time, and samples with a high density of donor?acceptor complexes (IDAC/Ibulk ≥ ~10%) showed good hydrophilicity (contact angle ≤ 20°) over 22 days. Larger amounts of basic Ti?OH relative to acidic OHbridge (ITi?OH/Ibridge ≥ 1) resulted in greater amounts of donor?acceptor complexes (IDAC/Ibulk ≥ ~10%). Thus, basic Ti?OH groups interact with H2O by forming a strong electrostatic donor?acceptor complex, leading to long-lasting hydrophilicity. Indeed, TiO2 was transformed to show long lasting hydrophilicity by high-density oxygen plasma treatment by forming sufficient Ti?OH groups and H2O molecules in the donor?acceptor complexes. Contact angle relaxation is closely related to the interactions between water molecules and the TiO2 surface in the dark. It is suggested that the relaxation depends on the number of electrostatic donor?acceptor complexes. This study provides new insight by linking theoretical studies with the experimental contact angle at the TiO2 surface in an ambient environment and is the first study that provides the presented relaxation mechanism.
关键词： Hydrophilicity,Sputtering,Plasma treatment,Contact angle relaxation,XPS analysis,Donor-acceptor complex,TiO2 thin films
更新于2025-09-23 15:22:29
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Insights into the Role of Plasma in Atmospheric Pressure Chemical Vapor Deposition of Titanium Dioxide Thin Films
摘要： In this work, the effect of plasma on the chemistry and morphology of coatings deposited by Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition (AP-PECVD) is investigated. To do so, plasma deposited amorphous titanium dioxide (TiO2) thin films are compared to thin films deposited using Atmospheric Pressure Chemical Vapor Deposition (AP-CVD) not involving the use of plasma. We focus here on the effect and the interest of plasma in the AP-PECVD process over AP-CVD for low substrate temperature deposition. The advantages of AP-PECVD over AP-CVD are often suggested in many articles however no direct evidence of the role of the plasma for TiO2 deposition at atmospheric pressure was reported. Hence, herein, the deposition via both methods is directly compared by depositing coatings with and without plasma using the same CVD reactor. Through the control of the plasma parameters, we are able to form low carbon coatings at low temperature with a deposition rate twice faster than AP-CVD, clearly showing the interest of plasma. Plasma enhanced methods are promising for the deposition of coatings at industrial scale over large surface and at high rate.
关键词： AP-PECVD,TiO2 thin films,Atmospheric Pressure Chemical Vapor Deposition,Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition,plasma,AP-CVD,low substrate temperature deposition
更新于2025-09-23 15:21:01
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Influence of oxygen vacancy on the response properties of TiO2 ultraviolet detector
摘要： In this paper, the effect of sputtering distance between target and substrate (DTS) on the structural, morphological and optical properties of TiO2 films were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that crystallite size and surface morphology were strongly dependent on DTS. The X-ray photoelectron spectroscopy (XPS) results showed that obvious three peaks including C1S, Ti2p and O1s could be clearly observed and binding energy was 285, 458 and 531 eV, respectively. For each sample, four peaks at about 386, 462, 527 and 595 nm in photoluminescence (PL) spectrum were observed and produced by intrinsic recombination, F center, F+ center and electrons transferred from 3d Ti3+ states to the deep levels OH?, respectively. Finally, photoresponse properties of UV detector based on TiO2 films were further analyzed and TiO2 UV detector prepared by DTS of 80 mm showed a high responsivity of 2.02 ×10-4 A/W and photosensitivity of 32.25, also, exhibited a fast response with a rise time (τr) of 0.98 s and fall time (τf) of 3.14 s.
关键词： UV detector,oxygen vacancy,TiO2 thin films,X-ray photoelectron spectroscopy
更新于2025-09-11 14:15:04