Abstract
Plasma-assisted chemical vapor deposition (PCVD) was applied for amorphous TiOx deposition on Pyrex-glass substrate at low temperature below 90˚C to control orientation of anatase-TiO2 layer by low pressure chemical vapor deposition (LPCVD) using TTIP-single precursor. Preferentially -oriented anatase-TiO2 layer was successfully deposited with the orientation ratio as high as 68% on the initial layer of the thickness around 70 nm. Contact angle water was quickly decreased by UV-irradiation on the highly -oriented TiO2 layer comparing with the layer directly deposited on glass, whereas surface roughness on the former was significantly reduced in comparison to that on the latter. Methyleneblue (MB) aqueous solution with the concentration of 2 mmol/L was used to evaluate photocatalytic property on the layer. Rate constant of MB-decomposition via first order kinetics increased with the orientation ratio above 60% was resulted in 2.3 × 10−1 min−1 for the layer with -orientation ratio of 68%, whereas the constant was 2.8 × 10−3 min−1 for the layer directly deposited on glass.
Highlights
Anatase-TiO2 with wide energy bandgap about 3.2 eV has been well recognized as useful material for photoinduced application using the hydrophilic property and the catalytic reactions [1] [2]
The calculated energy was in good agreement with the experimentally obtained value of 239 kJ/mol, which indicated the low pressure chemical vapor deposition (LPCVD) using TTIP single precursor in surface reaction region was limited by the TTIP-dissociation scheme
Since contact angle of water is decreased with increasing surface roughness on hydrophilic material as described by Wenzel’s relationship [18], the results suggests Ti-OH was more efficiently formed at the surface of the layer on 70 nm-thick initial layer than that of the layer directly deposited on glass because the roughness of the former was significantly lower than that of the latter
Summary
Anatase-TiO2 with wide energy bandgap about 3.2 eV has been well recognized as useful material for photoinduced application using the hydrophilic property and the catalytic reactions [1] [2]. Sol-gel, reactive sputtering, vacuum evaporation, chemical vapor deposition and so on have been studied to fabricate anatase-TiO2 layer [6]-[8], in which the orientation, the surface roughness, the defects etc. Tokita et al demonstrated , , and -oriented epitaxial growth of anatase-TiO2 layer deposition by CVD using titanium-tetra-iso-propoxide (TTIP) on C-sapphire, (110)MgO, (100)MgO and (100)SrTiO3 single crystal, respectively, and efficient decomposition of methyleneblue on (112)anatase-TiO2 by UV-irradiation in comparison to other oriented layers [10]. Initial TiOx layer deposited by plasma-assisted CVD (PCVD) at low temperature below 90 ̊C is used to control of the orientation of anatase-TiO2 layer on Pylex-glass by low-pressure CVD (LPCVD) using TTIP-single precursor, and the UV-induced hydrophilic property and the photocatalytic property in methyleneblue solution are demonstrated by using the LPCVD-TiO2 layer
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