臺灣博碩士論文加值系統

氣體感測器隨著科技的進步與民眾對於自身居住安全及環境保護的意識提高而被大量的使用。其中氧化鎵在高溫下穩定且具有半導體的特性，近年來經常被應用於感測還原性氣體。本研究將以真空蒸鍍熱氧化法來製備氧化鎵薄膜氣體感測器。並改變蒸鍍速度、升溫氣氛、氧化時間、氧化氣氛及氧化溫度，探討不同製備條件下氧化鎵薄膜之表面型態以及感測性質之影響。

實驗結果顯示，當蒸鍍速度快時，所得到的薄膜表面顆粒較大且平坦，但是感測度較差。升溫環境的不同，不僅大大的改變薄膜表面的型態，更使得半導體特性改變。而氧化溫度的提高以及氧化時間的增加，對薄膜的表面型態影響不大，但會使其半導體特性趨向於P型。

不同的蒸鍍速度所製備之氧化鎵薄膜，有不同的最佳感測溫度。而隨著感測溫度升高，其應答及回復時間都有縮短的現象。其感測度隨著酒精濃度的增加，也都有隨之增加的趨向。

Abstract
A large number of gas sensors are used with the progress of science and technology, the concern about living security and the consciousness of environmental protection. Among them, gallium oxide has the character of semiconductor and is stable under high temperature. Therefore, it is applied to detect the reducing gas frequently in recent years. This study uses rtheotaxial growth and thermal oxidation to prepare the gas sensor of gallium oxide. We probe into superficial morphology and influence of sensor properties in gallium oxide thin film that prepares under different preparing conditions, including the change of deposition rates, atmosphere of temperature rising, oxidation time, oxidation atmosphere and oxidation temperature.

The experimental result shows, when deposition rates is quick, the particles on the surface of thin film gets bigger and smoother, but the sensitivity is worse. Not only the morphology of the surface but also the electrical properties change significantly with different atmosphere of temperature rising. Rising oxidizing temperature and increasing oxidizing time have just a little effect on superficial morphology of the thin films, but the process makes its electrical properties trend towards the P type.

Each gallium oxide thin film prepared in different deposition rate has its own optimal operation temperature. Both the response time and the recovery time shorten as the operation temperature rises. Its sensitivity also increases with the rise for the concentration of ethanol.

目錄

中文摘要…………………………………………………………………...Ⅰ
英文摘要……………………………………………………………….......Ⅱ
致謝………………………………………………………………...…….. Ⅳ
目錄………………………………………………………………...………Ⅴ
表目錄…………………………………………………………………...…Ⅸ
圖目錄…………………………………………………………...…………Ⅹ
符號說明………………………………………………………...………ⅩⅢ

第一章 緒論………………………………………….…………..………..1
1.1簡介…………………………………………………………….……..2
1.2 研究發展與文獻回顧………………………………………………..6
1.3研究目標……………………………………………………………...9

第二章 理論回顧及分析………………………………………………...10
2.1 真空蒸鍍理論……………..………………………………………..10
2.1.1 真空理論…………………..…………………………………...10
2.1.2 蒸鍍理論…………………..…………………………………...13
2.2 薄膜成長機制與模式………………………………………18
2.2.1 蒸氣原子在基板的表面行為……………….………………18
2.2.2薄膜沉積的因素………………….…………………………….21
2.2.3薄膜的成長模式……………….……………………………….25
2.3 氣體感測器的工作原理……………………….………………..….28
2.3.1 蕭特基接觸…………………………………………………….29
2.3.2 氧氣的吸附與還原性氣體的作用…………………………….33
2.3.3氧空位…………………………………………………………..38
2.4 Ga2O3材料及結構簡介……………………..…………..………….40
2.5 文獻回顧……………………………………………………………42
2.6 研究動機……………………………………………………………44

第三章 實驗系統及操作………………………………..……………….45
3.1 實驗流程……………………………………………………………47
3.2 基板與材料的準備…………………………………………………48
3.3 真空蒸鍍系統………………………………………………………52
3.4 蒸鍍程序……………………………………………………………55
3.5 高溫氧化程序………………………………………………………56
3.6 結構分析……………………………………………………………57
3.7 電性量測及氣體偵測………………………………………………58

第四章 實驗結果與討論…………...……………………………………60
4.1 蒸鍍速率對薄膜型態的影響………………………………………61
4.2 不同氧化條件對薄膜型態的影響………………………………....64
4.2.1 升溫氣氛對薄膜的影響……………………………………….64
4.2.2 氣體流量對薄膜的影響……………………………………….67
4.2.3 氧氣濃度對薄膜的影響……………………………………….69
4.2.4 氧化溫度對薄膜的影響………………………….……………73
4.2.5 氧化時間對薄膜的影響……………………………………….77
4.3 XRD對氧化鎵薄膜之分析………………………….……...…….81
4.3.1 氧化溫度對晶相之影響……………………………………….81
4.3.2 氧化時間對晶相之影響……………………………………….84
4.4 不同製備條件下薄膜電性之探討…………………………………86
4.4.1蒸鍍速率對感測度的影響……………………………………..88
4.4.2不同升溫過程對感測性質的影響……………………………..90
4.4.3氧化氣氛對感測度的影響……………………………………..94
4.4.4 氧化時間對感測度的影響…………………………………….97
4.4.5氧化溫度對感測度的影響……………………………………..99
4.4.6 還原氣體濃度對感測度的影響……………………………...105
4.4.7 操作溫度對感測度的影響…………………………………...109
4.4.8 應答及回復時間…………………………………………...…111

第五章 結論…………………………………………………………….115

參考文獻………………………………………………………………….117
附錄……………………………………………………………………….123
自述……………………………………………………………………….124

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