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 ¢J. The rutile phase can be observed at the annealing temperature of 900 ¢J. 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 ¢J 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 ¢J. 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 ¢J 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.

Titanium oxide (TiO2) films have been actively investigated as many applications because of the mechanical and chemical durability, high refractive index and high transparency. In catalytic and electrochemical applications, it has been utilized as a stable semiconductor electrode for the conversion of solar energy into chemical or electrical energy. Uniform TiO2 films were deposited on conductive glass substrate (ITO/glass) by liquid phase deposition (LPD) with the aqueous solutions of ammonium hexafluoro-titanate and boric acid. Niobium oxide powder and Hydrofluoric acid which add deionized water were used to be Niobium doping solution. Undoped LPD-TiO2 has hydroxyl related defects and Li+ ions will be trapped to degrade the electrochromic durability. For niobium doping, the electrochromic characteristics were enhanced. Niobium doping in TiO2 can reduce hydroxyl related defects. The electrochromic durability was enhanced from 5¡Ñ103 to 1¡Ñ104 times. The transparency ratio was enhanced from 61 % to 70 % at the wavelength of 550 nm. In our experiment, TiO2 films morphology and thickness was characterized by scanning electron microscopy (SEM), structure was characterized by X-ray diffraction (XRD) and surface roughness was measured by atomic force microscopy (AFM), chemical properties was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR), optical properties was characterized by spectrophotometer (MP-100), and electrochromic characterized by cyclic voltammetry (CHI627C).

In this study, we deposit titanium dioxide (TiO2) on the indium tin oxide (ITO/glass) substrate by a liquid phase deposition (LPD) method as a buffer layer and coat TiO¬2 particles on LPD-TiO2 films by spin-coating method as anode of dye-sensitize solar cell (DSSC). In order to adjust the optical absorption edge of titanium dioxide to the visible light, we co-dope fluorine and nitrogen into TiO2 by LPD method and Ammonium Fluoride (NH4F). In our experiment, the morphology and thickness was characterized by scanning electron microscopy (SEM), structure was characterized by X-ray diffraction (XRD), chemical properties was characterized by electron spectroscope chemical analysis (ESCA), structural and spectral properties were characterized by ultraviolet-visible spectroscopy (UV-Vis) spectroscopy and current-voltage (I-V) characterization of solar cells was measured by B1500A. In our results, we enhance the performance of TiO2 as a DSSC`s anode, the open circuit voltage can reach to 0.71 V, the short circuit current can reach to 5.14 mA, the conversion efficiency can reach to 1.91 % and the fill factor can reach to 52.5 %.

No description available.

In this study, the characteristics of Nickel-doped LPD-TiO2 films on silicon substrate were investigated. In our experiment, we do some measurement about physical, chemical and electrical properties for undoped and Nickel-doped LPD-TiO2 films and discussed with them. The TiO2 film thickness was characterized by field emission scanning electron microscopy ( FE-SEM ), structure was characterized by X-ray diffraction (XRD), chemical properties was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and electrical properties was characterized by leakage current: current-voltage (B1500A) and dielectric constant: capacitance-voltage (4980A). For the electrical property improvements, we investigated the Ni-doped LPD-TiO2 films by the post-anneal treatments in nitrogen, oxygen and nitrous oxide ambient. For nickel doping, the nickel chloride was used as the doping solution and the electrical characteristics were improved. After thermal annealing in nitrous oxide at 700 oC, the dielectric constant of polycrystalline titanium oxide film is 29 and can be improved to 94 with nickel doping.

An uniform titanium oxide film was grown on indium tin oxide/glass substrate with the aqueous solutions of ammonium hexafluoro-titanate and boric acid. The as-deposition titanium oxide film shows good electrochromic property because of fluorine passivation on defects and dangling bonds. The transmittance of as-grown titanium oxide on indium tin oxide/glass with a thickness of 270 nm is about 85% at the wavelength of 550 nm. By 50 times electrochromic cycling test, the transparency ratio of TiO2 film is kept at 45% between fully colored state and fully bleached state at the wavelength of 550 nm. Under ultraviolet illumination, the growth of titanium oxide film grown is enhanced. The root mean squared value of surface roughness is improved from 3.723 to 0.523 nm. Higher fluorine concentration from (NH4)2TiF6 passivate defects and dangling bonds of titanium oxide during the growth. After 50 times electrochromic cycling test, the transparency ratio UV-TiO2 is improved from 37.5% to 42.4% at the wavelength of 550 nm. The electrical characteristics of nickel-doped titanium oxide films on p-type (100) silicon substrate by liquid phase deposition were investigated. For nickel doping, the nickel chloride was used as the doping solution and the electrical characteristics were improved. After thermal annealing in nitrous oxide at 700 oC, the dielectric constant of polycrystalline titanium oxide film is 29 and can be improved to 94 with nickel doping. Uniform nickel oxide film was grown on a conducting glass substrate with the aqueous solution of saturated NiF2¡E4H2O solution and H3BO3. The quality of NiO is improved after thermal annealing at 300 oC in air from the decrease of oxygen vacancy and better F ion passivation on defects and dangling bonds. The transmittance of as-deposited NiO/ITO/glass with a thickness of 100 nm is about 78% and improved to 88% after annealing at the wavelength of 550 nm. By the electrochromic cycling test 50 times on annealed NiO film, the transparency ratio is kept at 48% between fully colored state and fully bleached state at the wavelength of 550 nm. By the memory time test, the annealed LPD-NiO film has shorter memory time. The growth of nickel oxide film grown on indium-tin oxide/glass substrate by liquid phase deposition is enhanced under ultraviolet photo-irradiation was studied. a-Ni(OH)2 dominates the composition of as-grown NiO film. After thermal treatment at 300 oC,a-Ni(OH)2 is transformed into NiO. For thermally treated NiO under ultraviolet photo-irradiation, the recrystallization and the colored and bleached transmittance after 50 times electrochromic test were improved. Both improvements come from fluorine passivation. Transparent and conductive thin films consisting of p-type nickel oxide (NiO) semiconductors were prepared by liquid phase deposition. A resistivity of 8 x 10-1 -cm was obtained for NiO films prepared at liquid phase deposition. The transmittance of NiO is almost 70 % in the 550 nm wavelength was obtained for a 384.3 nm thick NiO film.

In this study, the characteristics of LPD-NiO, and lithium-doped LPD-NiO filmson glass substrate were investigated. In our experiment, we do some measurement about physical, chemical, electrical and optical properties for LPD-NiO and lithium-doped LPD-NiO films and discussed with them. The NiO film thickness was characterized by field emission scanning electron microscopy (FE-SEM), structure was characterized by X-ray diffraction (XRD), chemical properties were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). Electrical properties were characterized by four-point probe, and optical properties were characterized by a reflecting spectrograph. The thermal annealing was used to improve the characteristics of LPD-NiO and lithium-doped LPD-NiO films in nitrogen, air and nitrous oxide ambient. For lithium doping, the lithium chloride was used as the doping solution and the electrical characteristics were enhanced. After thermal annealing in air at 400 oC, the resistivity of NiO films is 7.5 ¡Ñ 10-1 ohm-cm and can be lowed to 7.2 ¡Ñ 10-3 ohm-cm with lithium doping.

High dielectric constant barium doped titanium silicon oxide films with equivalent oxide thickness below 1 nm can be prepared by liquid phase deposition. We learn from this research that the deposition rate of titanium silicon oxide films can be much enhanced by nitric acid incorporation, and the dielectric constant of materials can be increased by the dipole polarization from barium. The key parameter for the deposition rate, refractive index, and the dielectric constant of barium doped titanium silicon oxide is the molarity of barium nitrate. The electrical properties can be improved effectively by thermal annealing treatments. The optimum equivalent oxide thickness of barium doped titanium silicon oxide thin film is 0.9 nm with the optical thickness of 7.4 nm. The high dielectric constant can reach 31.9 and the leakage current density is 5 ¡Ñ 10-6 A/cm2 at the electrical field intensity of 5 MV/cm, which has high potential application for the next generation MOSFET.

Carbon nanotubes have been of great interest given their unique electronic and mechanical properties. Scholars have focused on the addition of carbon nanotubes to various matrices in order to develop novel materials. These new hybrid materials would combine the properties of both the nanotubes and the matrix of choice, which can both enhance the mechanical and electronic properties of the matrix material, and allow for the matrix to be used for other applications. In order to take advantage of the properties of the nanotubes, it is vital for them to be well dispersed in a solution or matrix as individual tubes, rather than as bundles. Additionally, it is cost effective to have individually dispersed tubes in a matrix. In order to individually disperse the tubes in the matrix, they can be pre-treated or functionalized via both covalent and non covalent processes. Subsequent to functionalization, the nanotubes can be coated with the matrix material or other metal compounds. This can help with the dispersion and interface interaction with the matrix material, or create materials with novel properties. This thesis focuses on conditions of growing various metal compounds or metal oxides on nanotubes using chemical bath deposition (CBD) and liquid phase deposition (LPD) methods. CBD and LPD use aqueous mediums for growth and deposition of compounds, which makes it both environmentally friendly and cost effective. Different pre-treatments are first employed on the nanotubes in order for them to be both well dispersed in solution and provide nucleation sites for the deposition and growth of various metal and metal oxides on the surface of the nanotubes. Once an ideal deposition is achieved, applications of the coated tubes are studied, tested and discussed.

High quality ammonium oxofluorotitanate discoid crystal is successfully grown on glass with an aqueous solution of ammonium hexafluorotitanate and boric acid at the molar ratio of 0.6. The concentration of hydrofluoric acid is less on the glass substrate surface and enhances the ammonium oxofluorotitanate nucleation growth. The growth rate is much higher than that grown on dioctadecyldimethylammonium. From the examinations of X-ray diffraction and high-resolution transmission electron microscopy, the crystal shows high crystalline quality and uniformity. Each titanium oxide octahedral is linked with fluorine and nitrogen atoms. Therefore, ammonium oxofluorotitanate has high potential to be thermally decomposed into high crystalline fluorine and nitrogen co-doped titanium oxide. A simple process for the preparation of nanocrystalline anatase phase titanium oxide converted from ammonium oxofluorotitanate by thermal treatment was developed. The nanocrystalline anatase phase titanium oxide shows a large bandgap reduction due to the co-doping of high concentrations of fluorine and nitrogen. Due to the excellent nanocrystalline quality and the co-doping of higher concentrations of fluorine and nitrogen at the thermal treatment temperature of 800 OC, it is 1.3 times the photocatalytic activities of P-25 due to the visble region usage of Hg lamp light source. The 11.2 times the visible photocatalytic activities of P-25 using blue light-emitting diode as the light source is obtained from thermal treatment temperature of 600 OC. There is one to one correspondence between carrier lifetime and photocatalytic activity. As a result, a highly reactive and visible-light-driven photocatalysis is achieved. The heterostructure of zinc selenide/titanium oxide and zinc sulfide/titanium oxide were prepared by metal-organic chemical vapor deposition on the above-prepared titanium oxide. The energy bandgap of zinc sulfide is much larger than that of titanium oxide and can act as a window for titanium oxide. It would not hinder titanium oxide absorption and preserve the role of fluorine and nitrogen co-doping. The energy bandgap of zinc selenide is near the maximum intensity of solar spectrum and acts as a sensitizer of titanium oxide. The lifetime of electron and hole pairs of heterostructure are about 240 and 207 nsec, which are longer than 65 nsec of titanium oxide prepared at 800 oC thermal treatment. Their photocatalytic activities are further improved to 2.0 and 1.5 times higher than that of commercial P-25. The photocatalysis of titanium oxide is very sensitive to the surface states. Titanium oxide surface defects can act as trapping sites for photo-induced holes and facilitate the separation of photo-induced carriers. Zinc selenide and zinc sulfide can passivate the surface well. It may say that titanium oxide surface defects removal has a negative impact. The density, height, diameter, PL wavelength and intensity of zinc selenide self-assembled quantum dots grown on zinc sulfide/gallium arsenide with the zinc sulfide thickness from 15 to 160 nm are studied. For a fixed 30 sec zinc selenide self-assembled quantum dots growth, it cannot be formed with the zinc sulfide thickness below 15 nm due to the close lattice match between zinc sulfide and gallium arsenide. The zinc sulfide/gallium arsenide is fully lattice relaxed with the zinc sulfide thickness higher than 130 nm examined by X-ray diffraction. The higher quality and density of zinc selenide self-assembled quantum dots can be obtained on zinc sulfide/gallium arsenide with the zinc sulfide thickness far beyond its critical thickness. The maximum zinc selenide self-assembled quantum dots density of 4.9 x 109 cm-2 with the strongest photoluminescence intensity is obtained at the zinc sulfide/gallium arsenide thickness of 130 nm. Clusters are formed on the surface of zinc selenide/gallium arsenide. The selenium segregation is the main mechanism for the formation of clusters. The dislocations will enhance the selenium segregation. Higher zinc selenide cluster corresponds to higher density of dislocations. The non-spherical cluster is formed from the mergence of the two clusters. High quality zinc oxide rods and zinc hydroxide slices are successfully grown on gallium arsenide with the aqueous solution of zinc nitrate and hexamethylenetetramine. The growth can be controlled by the appropriate nitric acid concentration incorporation in the solution. After thermal annealing, the zinc oxide slices transformed from zinc hydroxide slices can contribute much higher photocatalytic activity to 1.2 times to P-25.