||Liquid Phase Deposited (LPD) TiO2 film technology and the characterization of films were described in detail in this thesis. The LPD-TiO2 film can be utilized in electrochromic, photocatalyst and gas sensor devices. The optimum parameters for deposition of LPD-TiO2 were studied. |
First of all, we study the deposition properties and deposition parameter of LPD-TiO2 film. The effect of heating treatment on LPD-TiO2 film was investigated in this thesis. The as-deposited LPD-TiO2 film is amorphous and the TiO2 anatase phase can be obtained by annealing at 400 ℃. The rutile phase can be observed at the annealing temperature of 900 ℃. After annealing, the crystalling characteristic of LPD-TiO2 film can be improved and its refractive index can reach 2.46 annealed in O2 ambience. Its dielectric constant can be as high as 17 at annealing temperature of 700 ℃ in O2 ambience.
LPD-TiO2 film can deposit on GaAs substrate successfully. The GaAs was etched by the treatment solution during deposition. Therefore, Ga and As are contained in the LPD film. The C-V characterization can be improved at annealing 400 ℃. But the leakage current increases with higher annealing temperature.
The electrochromic (EC) phenomena of TiO2 have been first reported by Inoue et al., where the films are prepared by hydrolysis of titanium tetraoxide. The film shows cathodic coloration and turns dark blue. The LPD-TiO2 film was deposited at 40 ℃ with (NH4)2TiF6 in the process of 0.1 M and 0.2 M boric acid. The films were transparent in the visible range and can be colored in a 1M LiClO4 + propylene carbonate solution. The deposition rate can be controlled quite well at 43 nm/hours. The 270 nm thickness LPD-TiO2 film gives the best electrochromic characteristic.
In order to further strength the feasibility and enlarge the application of LPD-TiO2 film. The characterizations of Nb, Au and Pt doped LPD-TiO2 film were investigated. The concentrations of Nb and Au in the film can be controlled by adjusting the concentrations of Nb and Au source solution added into the treatment solution, respectively. The Nb, Au and Pt species in the LPD-TiO2 film are Nb2O5, metallic Au and Pt(OH)x, respectively. The crystallite size of metal-doped LPD-TiO2 film is smaller than that of pure LPD-TiO2 film.
The photocalytic activities of undoped and Nb-doped LPD-TiO2 film were investigated. The photocatalytic activity of Nb-doped LPD-TiO2 film is about four times higher than that of pure LPD-TiO2 film.
The gas sensing properties of undoped and Nb, Au and Pt-doped LPD-TiO2 films were investigated for oxygen detection sensitivity. Experimental results show that the Nb-doped LPD-TiO2 film displays the highest in oxygen detection, and the Nb-doped LPD-TiO2 film has also a shorter response time.