臺灣博碩士論文加值系統

本論文使用簡單、快速、製作成本低的超音波噴霧熱解法製備氟摻雜氧化錫 (FTO)薄膜。主要針對製備過程中基板的溫度、攜帶氣體中的氧氣濃度以及氟的摻雜量等因素對FTO薄膜性質的影響進行討論。
較高的基板溫度會使FTO薄膜的晶粒變大、厚度增加、表面變得粗糙，這些改變影響了其電子和光學性質。在本研究中攝氏四百度是最適合的沉積溫度，我們利用四百度來進行不同氧氣濃度、和不同氟摻雜量的實驗。當氧氣濃度為50%時，電阻值最低，在本實驗中使用的所有氟摻雜濃度之下都是如此。藉由電性和晶格結構及化學鍵的分析我們推測其原因為，50% 的氧氣濃度足夠薄膜呈現緻密的成長，而且此濃度尚不會導致氧空缺的減少。此外，氟的摻雜量提供載子，相較於未摻雜的氧化錫，使用原子比F/Sn = 0.25的摻雜量使載子濃度從1020上升到1021 cm-3，但過多的摻雜量會造成格隙型的缺陷和晶格團聚的現象，反而使載子濃度降低，對穿透度也有不良的影響。
經過許多參數的調整我們成功的做出擁有低的電阻率4.97 10-4Ω-cm和高的穿透度87%的FTO薄膜。相較於許多使用空氣作為攜帶氣體的噴霧熱解法沉積之FTO的研究，這個研究做出了更薄的薄膜 (250–350 nm)，卻維持相近的電阻率。因為較薄，所以做出來的穿透度 (87%)比許多其他研究更高。我們建議氧含量為50% 的攜帶氣體比空氣更適合沉積氟摻雜氧化錫薄膜。

Fluorine-doped tin oxide (FTO) thin films were fabricated by an ultrasonic spray pyrolysis (USP) method, which is simple, fast, and cost-effective. The effects of substrate temperature (TS), oxygen content in the carrier gas and fluorine doping concentration on the FTO thin films were studied in this thesis. The grain size, thickness, and surface roughness increased with increasing TS. These significant changes affected the opto-electrical properties of FTO films. The optimal TS was found to be 400˚C. FTO films under various oxygen contents and F-doping concentrations were further deposited at the optimal temperature (400˚C). The lowest resistivity was observed at O2 = 50%, regardless of different F doping concentrations. From the analyses of electrical properties, structure and chemical bonding, we suggest O2 = 50% is sufficient for dense films growth while maintaining the number of oxygen vacancies without. Besides, the carrier concentration was increased from 1020 to 1021 cm-3 for FTO films prepared with increasing from F/Sn = 0 (pure SnO2) to 0.25. In contrast, too much F-doping resulted in interstitials or clusters, leading to lower concentration and transmittance.
Under the optimal conditions, FTO thin films exhibited a higher transmittance up to 87% and low resistivity of 4.97×10-4 Ω-cm at relativity thinner film thickness, 250-350 nm. Overall, a carrier gas with 50% of oxygen is highly recommended, compared to the use of air as the carrier gas, for the deposition of FTO films using USP method.

Contents
摘要 i
Abstract ii
Acknowledgements iii
Contents iv
Table Captions vi
Figure Captions vii
Chapter 1 Introduction 1
1.1 Background 1
1.2 Overview of this thesis 2
Chapter 2 Literature Review 3
2.1 Ultrasonic spray pyrolysis (USP) 3
2.1.1 Ultrasonic atomization 4
2.1.2 Transportation of the resultant aerosol 6
2.1.3 Decomposition of the precursor on the substrate 6
2.2 General theory of FTO 8
2.2.1 Structure 8
2.2.2 Electrical properties 8
2.2.3 Optical transmittance 10
2.3 FTO by spray pyrolysis 11
2.3.1 Structure and morphology 11
2.3.2 Electrical properties 12
2.3.3 Optical transmittance 13
2.4 Motivation of changing the oxygen ratio in carrier gas during the FTO deposition by USP 13
Chapter 3 Experimental 17
3.1 FTO thin film deposition by USP 17
3.1.1 Preparation of the precursor solution 17
3.1.2 USP deposition equipment 17
3.1.3 FTO thin film deposition process 18
3.2 Instrumentation 21
3.2.1 Morphology and thickness measurement 21
3.2.2 Electrical properties 21
3.2.3 Structure 22
3.2.4 Optical transmittance 22
3.2.5 Specular reflectance Fourier-transform infrared spectroscopy (FTIR) 23
Chapter 4 Results and Discussion 25
4.1 Substrate temperature- dependent properties of FTO films 25
4.2 Thickness- dependent electrical properties 34
4.3 The effects of O2 content in the carrier gas ratio on the FTO films with various F-doping 38
4.3.1 Morphology 38
4.3.2 Structure and the amount of oxygen vacancies 45
4.3.3 Electrical properties 50
4.3.4 Optical transmittance 51
Chapter 5 Conclusions 60
References 62

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