臺灣博碩士論文加值系統

本研究採用反應磁控共濺鍍法沉積鈦酸鋅與鈦酸鋅摻雜鈮的薄膜於矽晶片、白金電極基板及石英玻璃，探討薄膜的鋅/鈦原子比例及退火處理的溫度對於其相變化、介電與光學特性及光觸媒效應的影響。以先進的材料分析設備對鈦酸鋅薄膜進行成分、結晶結構、表面形貌及粗糙度、微結構、介電與光學特性、光催化反應情況的研究，例如：化學分析電子儀(XPS)、低掠角X-光繞射分析儀(GIXRD)、場發射掃描式電子顯微鏡(FESEM)、原子力顯微鏡(AFM)、場發射穿透式電子顯微鏡(FETEM)、分光光譜儀(UV-VIS spectrophotometry)、電容量測儀(LCR meter)。此研究共分為四個主題進行探討：
第一個主題為探討薄膜的鋅/鈦原子比例(鈦含量從28.26 %到75.56 %)及退火溫度(600 °C到900 °C)對其相變化與微結構的影響，當薄膜的鈦含量比鋅多的時候，ZnTiO3與Zn2Ti3O8結晶相較容易形成；而當鋅較多的時候，Zn2TiO4較容易形成。其中，在薄膜鈦含量分別為62%及41%時，成功地製備單一Zn2Ti3O8及Zn2TiO4結晶相薄膜。利用FETEM分析薄膜晶粒尺寸與結晶相的關係，並且辨示出尖晶石Zn2TiO4結構及尖晶石陽離子缺陷型Zn2Ti3O8結構。
第二個主題為探討退火溫度對於Zn2Ti3O8薄膜的微結構與介電特性的影響，利用濺鍍法沉積薄膜於白金電極(Pt/Cr/SiO2/Si)基板上並退火500 °C時，成功地製備出單一Zn2Ti3O8結晶相薄膜之電容器結構。當退火700 °C時，較大尺寸的晶粒從薄膜中析出，利用FETEM鑑定其為ZnTiO3結晶相，並搭配FETEM橫截面高解析影像分析技術，證明Zn2Ti3O8薄膜與白金電極接觸性良好。特別的是，Zn2Ti3O8薄膜的介電特性第一次被發表：介電常數為32.9，介電損失為0.022在1 MHz的量測頻率下。
第三個主題為探討鈮摻雜在鈦酸鋅薄膜中對其相變化及介電特性的影響，此薄膜利用RF/DC磁控共濺鍍法沉積在白金電極(Pt/Cr/SiO2/Si)基板上。當鈮摻雜在鈦酸鋅薄膜中，於退火600 °C及700 °C時，鈮的存在會抑制Zn2Ti3O8結晶相的產生，並且降低ZnTiO3的分解溫度從900 °C降低至800 °C，此外，鈮的摻雜亦會提升薄膜的介電特性。在鈮含量為3.11 at. %及退火800 °C時，鈦酸鋅薄膜(ZnTiO3 + TiO2)的介電特性為最佳：介電常數為83.9，介電損失為0.023在1 MHz的量測頻率下。
第四個主題為探討退火溫度對Zn2TiO4薄膜的微結構與光觸媒效應的影響，當Zn2TiO4鍍在石英基材上時，為非晶質結構與二氧化鈦奈米晶共存。進行600 °C到900 °C的退火製程之後，形成Zn2TiO4結晶相。從FESEM觀察Zn2TiO4薄膜退火900 °C的表面形貌發現，具有高密度的面缺陷晶粒。進一步利用FETEM觀察面缺陷型態為疊差與退火雙晶。此薄膜經過分解亞甲基藍水溶液的實驗評估之後，發現初鍍之薄膜具有較佳的光觸媒活性。

The aim of this study is to prepare, characterize, and apply the zinc titanate thin films by reactive magnetron co-sputtering in Ar/O2 atmosphere. The effects of Zn : Ti atomic ratio and annealing temperature were studied on the crystalline behavior, dielectric, optical properties, and photocatalytic activity of zinc titanates thin films. The content of the thesis is divided into four sections.
In the first section, the zinc titanate thin films were deposited on Si substrates to understand the influence of Ti content (28.26 to 75.56 %) and annealing temperature (600 to 900 °C) on the phase transformation and microstructure of the films. The as-deposited Zn-Ti-O film has an amorphous microstructure. The films contained mixtures of the ZnTiO3, Zn2TiO4, Zn2Ti3O8, rutile-TiO2, cubic-ZnO, and hexagonal-ZnO depending on annealing temperature and Zn : Ti atomic ratio. Moreover, either Zn2TiO4 or Zn2Ti3O8 were successfully prepared in a single phase when the Ti content of the films were 41 % or 62 % at annealing temperature of 600 °C, respectively. The complete microstructural analysis of ZnTiO3, Zn2TiO4, and Zn2Ti3O8 phases are revealed by transmission electron microscopy, in which the extra (110), (210), and (211) reflections of Zn2Ti3O8 in spinel can be identified.
In the second section, microstructure and dielectric properties of Zn2Ti3O8 thin films deposited on Pt/Cr/SiO2/Si substrate via a DC reactive magnetron co-sputtering method are investigated. A single Zn2Ti3O8 phase appeared when the films were annealed at 500 °C and 600 °C for 1h. Transmission electron microscopy examination indicated that the film annealed at 700 °C was composed of Zn2Ti3O8 and ZnTiO3 with fine and large grains in microstructure, respectively. The study firstly reveals that the Zn2Ti3O8 thin films has the following properties at 1 MHz: dielectric constant = 32.9, tanδ = 0.022 at 600 °C annealing.
In the third section, the effect of Nb-doping on phase transformation, structural characterization and dielectric properties of zinc titanate thin films prepared by RF/DC magnetron co-sputtering is investigated. The Nb-doping inhibits the formation of Zn2Ti3O8 phase at 600 °C and 700 °C and reduces the decomposition temperature of ZnTiO3 from 900 °C to 800 °C. Furthermore, it is easier for Nb5+ ions to substitute Ti4+ sites of TiO2 than that of ZnTiO3 and Zn2TiO4. This causes an increase in dielectric constant of the films because the NbO6 octahedra in lattice can enhance the space charge polarization. The 3.11 at. % Nb doped Zn-Ti-O films has dielectric constant = 83.9 and tanδ = 0.023 at 1 MHz at 800 °C annealing.
In the final section, microstructure and photocatalytic activity of Zn2TiO4 thin films deposited on quartz by using DC reactive magnetron co-sputtering are studied. The Zn2TiO4 thin film consisted of irregular shape grains with highly planar defect after annealing at 900 °C. The planar defect such as stacking faults and annealed twins are completely revealed by transmission electron microscopy. Under UV light irradiation, the as-deposited thin films exhibit better photocatalytic activity than crystalline films.

誌 謝 I
摘要 II
Abstract IV
Table of Contents VI
List of Tables IX
List of Figures XI
Chapter 1 Introduction 1
1.1 Zinc Titanates Materials 1
1.2 Motivation 3
1.3 Thesis Overview 5
Chapter 2 Background and Literature Survey 8
2.1 Background 8
2.1.1 Sputter Deposition 8
2.1.1.1 Introduction 8
2.1.1.2 Energy and Kinematics of Sputtered Atoms 8
2.1.1.3 Direct Current (DC) Plasmas 9
2.1.1.4 RF Plasmas 11
2.1.1.5 Magnetron Sputtering 11
2.1.1.6 Reactive Sputter Deposition 13
2.1.2 Zinc Titanates Structure 13
2.2 Literature Survey for Dielectric Properties of Zinc Titanates 15
Chapter 3 Experimental Procedure 27
3.1 Experimental Flow Chart 27
3.2 Preparation of Zinc Titanate Thin Films 28
3.2.1 Deposition of the Zn-Ti-O Thin Films 28
3.2.2 Deposition of the Zn2Ti3O8 Thin Films 28
3.2.3 Deposition of the Nb Doped Zinc Titanate Thin Films 29
3.2.4 Deposition of the Zn2TiO4 Thin Films 30
3.3 Characterization 30
3.3.1 X-ray Diffractometry (XRD) 30
3.3.2 Field-Emission Scanning Electron Microscopy (FE-SEM) 31
3.3.3 Atomic Force Microscopy (AFM) 31
3.3.4 Field-Emission Transmission Electron Microscopy (FE-TEM) 31
3.3.5 X-ray Photoelectron Spectroscopy (XPS) 31
3.3.6 UV-visible Spectrophotometry 32
3.3.7 Dielectric Properties Measurements 32
3.3.8 Photocatalytic Activity Measurements for Methylene Blue (MB) Degradation 33
Chapter 4 Results and Discussion 42
4.1 Crystallization, Phase Transformation and Microstructure of Sputtering-prepared Zinc Titanate Thin Films: Optimization of Annealing Condition Based on Zn: Ti Atomic Ratio 42
4.1.1 Chemical Composition 42
4.1.2 Crystal Structure 42
4.1.3 Morphology 46
4.1.4 Microstructure 47
4.2 Effect of Annealing on Microstructure and Dielectric Properties of Zn2Ti3O8 Thin Films by Reactive Co-sputtering 60
4.2.1 Crystal Structure 60
4.2.2 Morphology 61
4.2.3 Microstructure 61
4.2.4 Dielectric Properties 62
4.3 Phase Transformation, Structural Characterization and Dielectric Properties of Nb Doped Zinc Titanate Thin Films Prepared by Co-sputtering Method 70
4.3.1 Effect of Annealing Temperature on Undoped Zinc Titanate Thin Films 70
4.3.1.1 Chemical Composition 70
4.3.1.2 Crystal Structure 70
4.3.1.3 Morphology 70
4.3.2 Effect of Nb Dopants on Zinc Titanate Thin Films 71
4.3.2.1 Chemical Composition 71
4.3.2.2 Crystal Structure 71
4.3.2.3 Morphology 73
4.3.3 Effect of Nb Concentration on Zinc Titanate Thin Films 73
4.3.3.1 Crystal Structure 73
4.3.3.2 Morphology 75
4.3.4 Dielectric Properties 76
4.4 Microstructure and Photocatalytic Activity of Zn2TiO4 Thin Films Deposited by DC Magnetron Co-sputtering 96
4.4.1 Chemical Composition 96
4.4.2 Crystal Structure 96
4.4.3 Morphology 96
4.4.4 Microstructure 97
4.4.5 Optical Characteristics 99
4.4.6 Photocatalysis 100
Chapter 5 Conclusion 113
References 116
Vita and Publication List 129

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