臺灣博碩士論文加值系統

近年來半導體薄膜應用於氣體感測上的使用非常廣泛，其主要感測機制乃是利用半導體薄膜在不同氣體下其導電性質不同所致，而由感測器電阻值的變化可求得其對氣體之感測度。
本研究將以真空蒸鍍熱氧化法製備摻雜鈦、鉑之氧化鎵薄膜氣體感測器，並藉由SEM、XRD分析其薄膜之型態及晶相，再以酒精作為感測氣體進行感測性質之測量，並探討在不同摻雜金屬、摻雜製程及摻雜濃度時對感測性質之影響。
實驗結果顯示，內部摻雜不同金屬之鎵薄膜氧化後所呈現的薄膜型態差異甚大，新產生的奈米結構(奈米帶及奈米線)將影響感測度之優劣，適當摻雜濃度可得到較高之感測度。表面摻雜鉑時則發現，表面金屬在感測時會產生聚集現象，導致感測時電阻持續上升及不連續之現象。
摻雜濃度不僅影響感測度，適當摻雜可降低最佳操作溫度，若過度摻雜使原本電性發生轉變，最佳操作溫度則明顯升高。而應答及回覆時間隨著摻雜濃度增加有下降的趨勢。
實驗過程中發現，感測時若有水氣的存在會使回復電阻升高，而升高的量則依據水氣濃度之多寡而定，且此現象為一不可逆反應，因此本實驗所製備之薄膜對水氣有極高之不穩定性。

Thin-film semiconductor is of use in an extremely wide of application, in recent years. The major sensing mechanism of semiconductor gas sensor is base on the change of electrical properties with gas composition, the gas sensitivity can be calculated as the ratio of the different resistances.In this paper, the Ti- and Pt- doped Ga2O3 thin films were prepared by rtheotaxial growth and thermal oxidation (RGTO). The morphology and crystallization of the thin films have been evaluated by SEM and XRD. In this study the sensing properties for ethanol were measured as functions of different dopants, doping process and dopant concentration.
The result shows that inner doping of Ti or Pt leads to an obvious change in morphology, and the nanostructures (nanoribbons and nanowires) affect the sensitivity of thin film and suitable dopant concentration can obtain the higher sensitivity. When the thin film doped with Pt on the surface, larger clusters are created during sensing and lead the resistance increasing and uncontinuous.
Dopant concentration influences sensitivity and lowers the optimum sensing temperature, which rises obviously when electrical properties convert p-type into n-type due to exceeding doping. The response time and recovery time decrease with increasing dopant concentration.
And we found that the response resistance rises due to the existence of water vapor during sensing, and it is irreversible. The variation of resistance depends on the water vapor concentration. So that the thin films prepared in this study are unstable to humidity.

中文摘要………………………………………………………………Ⅰ
英文摘要………………………………………………………………Ⅱ
目錄……………………………………………………………………Ⅲ
表目錄…………………………………………………………………Ⅶ
圖目錄…………………………………………………………………Ⅷ
符號說明……………………………………………………………ⅩⅢ


第一章
緒論………………………………………………………………………1
1.1 簡介…………………………………………………………………1
1.2 研究發展與文獻回顧………………………………………………8
1.3 研究目標…………………………………………………………12

第二章
理論回顧及分析………………………………………………………13
2.1 真空蒸鍍理論……………………………………………………13
2.1.1 真空理論……………………………………………………13
2.1.2 蒸鍍理論………………………………………………………15
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摻雜理論……………………………………………………………40
2.4.1 內部摻雜……………………………………………………40
2.4.2表面摻雜………………………………………………………41
2.5文獻回顧……………………………………………………………44

第三章
實驗系統及操作………………………………………………………47
3.1 實驗流程…………………………………………………………50
3.2 基板與材料的準備………………………………………………51
3.3 真空蒸鍍系統……………………………………………………55

3.4 蒸鍍程序…………………………………………………………58
3.5 高溫氧化程序……………………………………………………59
3.6 結構分析…………………………………………………………59
3.7 電性量測及氣體偵測……………………………………………60

第四章
實驗結果與討論………………………………………………………62
4.1摻雜Ti對薄膜型態之影響…………………………………………63
4.1.1 混合摻雜Ti - 蒸鍍過程對薄膜型態之影響………………63
4.1.2 混合摻雜Ti - 氧化過後對薄膜型態之影響………………65
4.1.3 表面摻雜Ti - 氧化過後對薄膜型態之影響………………65
4.2摻雜Pt對薄膜型態之影響…………………………………………68
4.2.1 表面摻雜Pt - 溫度對表面Pt之影響………………………68
4.2.2 內部摻雜Pt - 氧化過後對薄膜型態之影響………………71
4.3 XRD對摻雜後氧化鎵薄膜之分析……………………………… 73
4.3.1 混合摻雜Ti對晶相之影響………………………………… 73
4.3.2 內部摻雜Pt熱處理對晶相之影響………………………… 75
4.3.3 內部摻雜Pt對晶相之影響………………………………… 77
4.4摻雜對感測性質之影響……………………………………………79
4.4.1摻雜Ti對感測性質之探討……………………………………81
4.4.2 摻雜Pt對感測性質之探討……………………… …………85
4.4.2.1表面摻雜-Pt對感測性質之影響 ……………………85
4.4.2.2內部摻雜-Pt對感測性質之影響……………………93
4.5溼度對感測穩定性之影響………………………………………99
4.6操作溫度對感測度之影響………………………………………101
4.6.1摻雜Ti - 操作溫度對感測度之影響……………………… 101

4.6.2摻雜Pt - 操作溫度對感測度之影響……………………… 110
4.7摻雜對應答時間及回復時間的影響……………………………115

第五章
結論……………………………………………………………………120
未來工作方向…………………………………………………………122
參考文獻………………………………………………………………123

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