Plasma Injection Preparation And Its Performance Study Of Carbon Doped Tio2 Thin Film

Titanium dioxide (TiO2) is among the most promising materials for photocatalytic and photoelectrochemcial applications due to its low cost, photostability, chemical inertness and nontoxicity. In photocatalysis, it has been used to purify wastewater or air by the organic compounds decomposition and to produce hydrogen by water splitting. In photoelectrochemistry, it has been used dye-sensitized in solar cells. However, the application of TiO2is hindered because it is active only under ultraviolet light illumination due to its wide band gap of3.2-3.5eV.Therefore,much effort has been made to modify its band gap energy in order to enhance its absorption in the visible light region. In this thesis TiO2thin films were fabricated by RF magnetron sputtering on titanium substrates at room temperature, and the thickness was detected about100nm by a stephight profiler. Films obtained then were implanted with carbon at different power levels to investigate its influence over the diffusion of carbon while by controlling implanting time, C-implanted TiO2films with various carbon contents were prepared. To investigate the microstructures, valence states and optical characteristics of each sample, X-ray diffraction (XRD), X-ray photoelectron spectroscopy(XPS),and UV-Vis diffuse reflection spectra (DRS) were employed. Sample’s photoelectric property was evaluated on an electrochemical workstation under visible light, using a xenon lamp as illuminant with all ultraviolet and infrared eliminated.Results attained indicate that all samples demonstrate anatase phase and the implanted carbon may exist as interstitial or substitutive ions, where the former only squeezed into the TiO2lattice thereby resulted in greater distortion, and the later would replace lattice oxygen, curtailed the original energy gap of TiO2and brought about a notable red shift of the absorption spectra. No Ti-C bonds were observed in the XPS spectra while a great number of interstitial carbons were detected. Particles size decreased as carbon content grew, which is the consequence of enhanced distortion resulting from implantation. It was also substantiated that the implanting amount, together with the depth of distribution that was mainly determined by the implanting power, could exert a significant influence on film’s microstructures as well as the valence states of elements. In the photocurrent experiments, all C-implanted samples presented enhanced photoelectric property, and the strongest photocurrent, which2.5times that of TiO2(observed as anatase), occurred as the implantation lasted30minutes with a power of12kv. It was also confirmed that employing higher power or further prolonging the implanting time was abortive to improve the photocurrent.