Investigation of photo-induced superhydrophilicity of TiO2-based thin films deposited by pulsed-DC reactive magnetron sputtering

• Main Authors: Man-Chun Liao, 廖曼鈞
• Other Authors: Giin-Shan Chen
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/77296795213182088027

碩士 === 逢甲大學 === 材料科學所 === 97 === This dissertation employs conventional- and pulsed-DC reactive (Ar/O2) sputtering deposition processes, in conjunction with in-situ monitors of (a) cathode voltage/current, (b) partial oxygen pressure, and (c) optical emission as a function of the value of oxygen flow rate, to obtain the optimal processing parameters (reactive atmosphere, substrate temperature and bias, and plasma-excitation type) for the fabrication of TiO2 thin films exhibiting photo-induced hydrophilicity, anti-fogging and self-cleaning properties. First, TiO2 films were deposited by conventional-DC reactive sputtering deposition under various substrate temperatures (250-400℃) and biases (from－100 V to ＋100 V). X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were used to observe differences in films’ microstructure. These analyses confirmed that controlling the temperature and bias at 300℃ and －50 V (or 0 V) favors the formation of anatase TiO2 (A-TiO2), deemed as high potential for hydrophilicity and anti-fogging applications. While the crystallinity of the TiO2 films can be further improved by employing the above mentioned processing parameters in conjunction with pulsed-DC magnetron sputtering, X-ray photoelectron spectroscopy (XPS) revealed that the surfaces of the TiO2 films can be contaminated by the sodium originated from the soda-lime glass substrates. This contamination renders the sample films after photon irradiation and cycling test to give high values of water contact angle ranging from 10 to 40�a. Nonetheless, using the soda-lime glass/TiNx/TiO2 dual-layered structure not only can effectively inhibit the outward diffusion of sodium, but also promote the crystallization of the film. These improvements result in a TiO2 films having long-last hydrophilicity of water contact angles as small as 7-9�a. Mechanisms behind the hydrophilicity improvement will be elucidated based on (a) experimental results of XRD, XPS, etc. and (b) previous literature findings.