臺灣博碩士論文加值系統

本論文旨在討論有機薄膜電晶體主動層與源極/汲極電極之間所產生的介面問題，首先利用不同載子傳輸型態的P-type(NPB)與N-type(Alq3)的單層緩衝層以探討其對P型通道有機薄膜電晶體的影響。接著再利用P-type(NPB)與N-type(Alq3)交互堆疊，並比較不同緩衝層結構對元件特性的影響；元件結構為ITO/PMMA(400 nm)/Pentacene(70 nm)/緩衝層(6 nm)/Ag。
實驗結果發現，當完成主動層pentacene蒸鍍後，堆疊NPB/Alq3的緩衝層應用在有機薄膜電晶體上有最佳的特性，當元件操作於VGS=VDS=-50 V的條件下，其飽和電流(IDS)從-2.06 μA提升到-9.65 μA，開關電流比(ION/OFF)從6.5×104提升至6.7×105，載子移動率(μ)從0.12 cm2/Vs提升至0.31 cm2/Vs，臨界電壓(VT)則從-24.2 V降低到-16.8 V。推論由NPB/Alq3之薄膜所組成之緩衝層因產生負耦極化並且有效調整能階差，相對提升了電極功函數，介面接觸電阻減少及主動層與金屬電極間能障差降低使載子較易注入主動層，故有效提升有機薄膜電晶體之載子移動率(μ)。

Organic thin-film transistors (OTFTs) with various buffer layers between the active layer and source/drain electrodes were investigated. NPB and/or Alq3 ultrathin layers are inserted between the pentacene and Ag (source-drain electrodes) to improve the performance of OTFTs. The structure was ITO glass/PMMA(400 nm)/pentacene(70 nm)/buffer layers(6 nm)/Ag.
Experimental results show that the performance of OTFTs was improved using the stacked buffer layer of NPB/Alq3. Compared with the control device, the output current (IDS) increases from -2.06 μA to -9.65 μA, on/off current ratio (ION/OFF) increases from 6.5×104 to 6.7×105, field-effect mobility (μ) increases from 0.12 cm2/Vs to 0.31 cm2/Vs, and threshold voltage (VT) decreases from -24.2 V to -16.8 V. The stacked buffer layer, NPB/Alq3, provides not only increased work function of source/drain electrodes but reduced interface contact resistance and then enhances carrier injection into the active layer.

摘要I
ABSTRACT II
誌謝III
目錄IV
表目錄VI
圖目錄VII
第一章 緒論1
1.1 研究背景1
1.2 研究動機與目的2
第二章 基礎理論3
2.1 有機半導體簡介3
2.1.1 有機光電半導體的發展3
2.1.2 有機半導體傳輸機制3
2.2 有機薄膜電晶體之簡介4
2.2.1 有機薄膜電晶體結構與類型5
2.2.2 有機薄膜電晶體半導體材料5
2.2.3 有機薄膜電晶體操作原理6
2.3 有機薄膜電晶體之參數6
2.3.1 載子移動率(Mobility，μ)7
2.3.2 臨界電壓(Threshold voltage，VT)7
2.3.3 開關電流比(ON/OFF current ratio)7
2.4 Transmission Line Method (TLM)8
2.4.1 有機薄膜電晶體接觸電阻公式8
2.4.2 接觸電阻與介面耦極(interface-dipole)8
第三章 實驗操作與設備10
3.1 實驗流程規劃10
3.2 實驗材料10
3.2.1 基板與閘極電極10
3.2.2 閘極介電層11
3.2.3 主動層11
3.2.4 緩衝層11
3.2.5 源極/汲極電極12
3.3 實驗儀器設備12
3.3.1 製程儀器設備12
3.3.2 量測儀器設備13
3.4 實驗方法與步驟14
3.4.1 基板清洗與處理14
3.4.2 介電層塗佈14
3.4.3 有機薄膜蒸鍍15
3.4.4 源極/汲極電極蒸鍍16
3.5 實驗量測16
3.5.1 介電層物理量測16
3.5.2 有機薄膜電晶體電性量測16
3.5.3 接觸電阻量測17
第四章 結果與討論18
4.1 元件電性量測18
4.1.1 基本元件製作與量測18
4.1.2 單層緩衝層元件特性18
4.1.3 堆疊式緩衝層元件特性19
4.2 接觸電阻及通道電阻對於有機薄膜電晶體的影響20
4.3 紫外光電子能譜儀分析21
4.3.1 基本元件21
4.3.2 以單層NPB為緩衝層21
4.3.3 以單層Alq3為緩衝層22
4.3.4 以堆疊式Alq3/NPB為緩衝層23
4.3.5 以堆疊式NPB/Alq3為緩衝層23
第五章 結論25
參考文獻26
表目錄
表1.1 有機及無機薄膜電晶體特性比較29
表2.1 有機光電半導體及元件發展大事紀30
表2.2 有機及無機半導體特性之差異31
表2.3 金屬與半導體接面能帶的關係31
表3.1 五環素(Pentacene)之性質32
表3.2 常用金屬之功函數與本實驗用半導體材料的HOMO 32
表4.1 不同緩衝層之OTFT特性比較33
表4.2 不同緩衝層之OTFT元件隨閘極電壓變化的接觸電阻33
圖目錄
圖2.1 (a)鍵結模型(bond model)(b)能帶模型(band model)34
圖2.2 無機半導體載子傳輸示意圖35
圖2.3 有機半導體載子傳輸示意圖35
圖2.4 有機薄膜電晶體結構種類36
圖2.5 元件不同偏壓下載子之分佈情形37
圖2.6 有機薄膜電晶體元件阻抗示意圖38
圖2.7 金屬與半導體接觸前後之情形39
圖3.1 實驗規劃流程圖40
圖3.2 元件結構圖41
圖3.3 聚甲基丙烯酸甲酯(PMMA)分子結構圖42
圖3.4 Pentacene(五環素)分子結構圖42
圖3.5 NPB分子結構圖42
圖3.6 Alq3分子結構圖42
圖3.7 主動層、緩衝層、電極材料能階關係圖43
圖3.8 真空蒸鍍系統簡示圖44
圖3.9 元件電特性量測設備架構圖45
圖3.10 紫外光電子能譜儀46
圖3.11 元件製程示意圖47
圖3.12 不同轉速對介電層厚度之關係48
圖3.13 元件施加偏壓示意圖49
圖3.14 不同通道長之OTFT元件完成圖49
圖4.1 (a)未加緩衝層之OTFT元件輸出特性曲線(b)未加緩衝層之OTFT元件轉移特性曲線50
圖4.2 (a)NPB緩衝層之OTFT元件輸出特性曲線(b)NPB緩衝層之OTFT元件轉移特性曲線51
圖4.3 (a)Alq3緩衝層之OTFT元件輸出特性曲線(b)Alq3緩衝層之OTFT元件轉移特性曲線52
圖4.4 (a)Alq3/NPB緩衝層之OTFT元件輸出特性曲線(b)Alq3/NPB緩衝層之OTFT元件轉移特性曲線53
圖4.5 (a)NPB/Alq3緩衝層之OTFT元件輸出特性曲線(b)NPB/Alq3緩衝層之OTFT元件轉移特性曲線54
圖4.6 不同緩衝層之OTFT元件特性轉移特性曲線整理55
圖4.7 未加緩衝層之OTFT元件Rtot-L關係圖55
圖4.8 NPB緩衝層之OTFT元件Rtot-L關係圖56
圖4.9 Alq3緩衝層之OTFT元件Rtot-L關係圖56
圖4.10 Alq3/NPB緩衝層之OTFT元件Rtot-L關係圖57
圖4.11 NPB/Alq3緩衝層之OTFT元件Rtot-L關係圖57
圖4.12 不同緩衝層之OTFT元件Rc-VGS比較圖58
圖4.13 (a)未加緩衝層之OTFT元件紫外光電子能譜圖(b)未加緩衝層之OTFT元件能階圖59
圖4.14 (a)NPB緩衝層之OTFT元件紫外光電子能譜圖(b)NPB緩衝層之OTFT元件能階圖60
圖4.15 (a)Alq3緩衝層之OTFT元件紫外光電子能譜圖(b)Alq3緩衝層之OTFT元件能階圖61
圖4.16 (a)Alq3/NPB緩衝層之OTFT元件紫外光電子能譜圖(b)Alq3/NPB緩衝層之OTFT元件能階圖62
圖4.17 (a)NPB/Alq3緩衝層之OTFT元件紫外光電子能譜圖(b)NPB/Alq3緩衝層之OTFT元件能階圖63

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