本篇論文的目的主要是利用液相沉積法成長二氧化鈦膜 , 摻雜鈮金屬並探討其光催化分解有機物亞甲基藍水溶液特性與對氧氣靈敏度之感測能力。利用液相沉積法於透明康寧玻璃基板上成長摻雜鈮金屬之二氧化鈦薄膜 , 其過程簡單、成本低廉、且成長溫度低 (40 oC) , 因此值得廣泛研究與討論。利用掃描式電子顯微鏡( SEM) 、拉曼光譜 (Raman Spectroscopy) 探討薄膜特性。光電子能譜儀 (ESCA)探討鈮金屬於膜中之成份分析。並由實驗結果顯示光催化特性與氧氣感測能力。

TiO2 is a fascinating material proving its usefulness in a wide range of applications. In photocatalytic and gas sensitization applications, it has been utilized as a stable semiconductor for the organic matter of waste water cleaning and impetus on environmental consciousness the need for highly efficient combustion engines, controlled industrial processes and monitoring the hazardous gas level in the environment.
Nanocrystalline TiO2 modified with Nb incorporation has been produced by LPD technique that deposited at 40 oC with (NH4)2TiF6 for 0.2 M, and 0.6 M for boric acid and a few mount of Nb solution. The deposition rate can be controlled perfectly about 40-50 nm/h. The addition of Nb stabilizes the anatase phase and retards the grain growth during high temperature annealing.
XRD and RAMAN spectra of undoped and Nb doped samples show that the undoped one has converted to rutile at 900 oC, meanwhile the doped one remains anatase phase. Nanocrystalline films stabilize at 800 oC with grain size of about 7 nm have successfully been synthesized by the additives of Nb, which appear to be an adequate dopant to improve the photocatalytic and gas sensor performances. The ability of niobium introduction is of retarding the anatase to rutile transformation and hindering its grain growth.

CONTENTS ................................................................................................I
LIST OF FIGURES IV
LIST OF TABLES VI
ABSTRACT VII

Chapter 1 Introduction 1
1-1 Developments in gas sensors 1
1-2 Photocatalytic property of TiO2 film ……………….…………..........2
1-3 Properties of titanium dioxide 3
1-4 Comparison of deposition methods of TiO2 4
1-5 Background of LPD………………………………………….............5
1-6 Motivation of LPD-TiO2……………………………………………..6
1-7 Mechanisms of LPD-TiO2…………………………………………....6
Reference ………………………………………………………………...11
Chapter 2 Experiments…………..………………………………………...19
2-1 Liquid phase deposition system 19
2-2 Deposition procedures 19
2-2.1 Corning glass substrate (type1737) cleaning procedures….…...19
2-2.2 Preparation of deposition solution…………………..................20
2-2.3 LPD-TiO2 processes 21
2-2.4 Preparation of doping treatment solution 21
2-2.5 LPD-doped niobium TiO2 films processes 22
2-3 Annealing treatment 22
2-4 Characteristics ......22
2-4-1 Physical property ....22
2-4-2 Chemical property……………………………………….............23
2-5 The process affecting photocatalytic destruction of methylene blue…...23
2-6 The process of gas sensing by un-doped and doped LPD-TiO2 thin film…………….........……………………………………………….....24
Chapter 3 Result and Discussion ….30
3-1 Hydrolysis reactions of (NH4)2TiF6.……………………….…..........….30
3-2 Physical properties of as-deposited Nb doped TiO2 films .....31
3-2.1 Deposition rate of Nb doped TiO2 film in deposition solution .................................................................................................................31
3-2.2 XRD analysis of Nb Doped TiO2 film on Corning glass substrate .....32
3-2.2.1 Influence of the annealing temperature........................32
3-2.3 SEM Cross-sectional and Top Views of Nb Doped TiO2 film on Corning glass substrate .34
3-2.4 Raman spectra analysis of Nb doped TiO2 film on Corning glass substrate...........................................................................35
3-2.4.1 Influence of the annealing temperature.........................35
3-2.4.2 Influence of the Nb loading percentage.........................36
3-3 Chemical properties of As-deposited Nb doped TiO2 films 36
3-3.1 Analysis of ESCA spectra 36
3-4 Crystal size 38
3-5 The relationship between the crystal size and the heat-treat process time of TiO2 and Nb doped TiO2 films.................................................39

3-6 Photocatalytic property 40
3-6.1 Mechanisms of TiO2 photocatalysis...........................................40
3-6.2 Influence of the annealing temperature...................................43
3-6.3 Influence of the Nb doping TiO2 thin film.................................44
3.7 Gas sensing property............................................................................46
3-7.1.1The sensing mechanism of the gas sensor................................46
3-7.1.2 The sensing property...............................................................46
3-7.1.3 Absorbability of the oxygen of the gas sensor........................47
3-7.1.4 Absorbability of the reducing gas of the gas sensor................48
3-7.2 Oxygen sensing properties of LPD film.....................................48
3-7.3 The effect of particle size and crystal structures on gas sensing properties.....................................................................................49
Reference...................................................................................................71
CHAPTER 4 Conclusions ............................................................................74












LIST OF FIGURES

Figure 1.1 Comparison of crystal structures of TiO2 (Rutile and Anatase)....8
Figure.2-1 Schematic diagram of Liquid Phase Deposition (LPD) system..26
Figure 2-2 LPD-TiO2 deposition flowchart...................................................27
Figure 2-3 LPD-Nb doped TiO2 deposition flowchart..................................28
Figure 2-4 Schematic of gas sensing measurement system..........................29
Figure 2-5 View of gas sensor chamber........................................................29
Figure 3-1 Deposition rate of pure and Nb doped TiO2 films at the deposition temperature of 40

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