臺灣博碩士論文加值系統

隨著可攜式電子裝置的普及和尺寸的微小化，電源供應問題成為發展瓶頸，科學家們希望能直接從環境中獲取能源，因此開始研究奈米發電機的應用。奈米發電機是一種能夠直接將環境中的機械能轉換為電能的裝置，不僅對環境無害，能源的取得也相當容易。近年來奈米發電機的開發已有一定的基礎，未來將朝擴大應用範圍的目標前進。氧化鋅(zinc oxide, ZnO)是一種II-VI族的n型半導體，擁有直接且寬的能隙(約3.3 eV)、高的激子束縛能(室溫下約60 meV)與c軸優選成長取向之纖鋅礦結構。由於其獨特的光學與電學性質，氧化鋅被應用在許多電子元件上，如奈米發電機、光感測器、發光二極體及感測器等。
氧化鋅的壓電係數約為12.4 pm/V，文獻中有許多方法能提升其壓電係數，而最有效率的方法便是化學摻雜。化學摻雜能改變晶格結構中的不對稱性，使材料在受到外加應力的同時產生更強的壓電電位，進而提升壓電係數的表現。本實驗利用氧化鋅靶與氧化釔靶，透過磁控射頻濺鍍系統進行共濺鍍，在固定的基板溫度(250℃)與工作壓力(6×10-2 torr)下，藉由調控氧化釔靶的濺鍍功率沉積不同摻雜量的氧化鋅薄膜於矽基板上，並探討摻雜量對於薄膜壓電係數的影響，找出最佳壓電係數的薄膜用於開發壓電型奈米發電機。
實驗結果顯示，透過濺鍍功率的調整，確實能成功改變釔原子在氧化鋅內的濃度，而製備出的薄膜均呈現c軸成長優選取向之柱狀纖鋅礦結構，該結構有助於壓電係數的上升，而薄膜的結晶性亦隨微量的釔摻雜而提升；但隨著釔含量增加，薄膜開始出現不規則狀晶粒，結晶性也開始下降。釔原子的摻雜置換了鋅原子使晶格發生扭曲並造成薄膜內部應力。而原先不具備鐵電性質的氧化鋅也因釔原子佔據四面體中非中心位置導致其呈現鐵電性質，研究顯示鐵電材料的自發極化效應能大幅提高其壓電表現，使其壓電係數有明顯的上升。在比較釔含量與薄膜之壓電係數後可以發現：當釔含量約為1.6 a.t.%時，薄膜的壓電係數提高至49.6 pm/V，與未摻雜的氧化鋅相比高了4倍，證實元素的摻雜對於氧化鋅的壓電性質具有顯著的上升，而造成此結果的原因可大致歸類於晶格結構的改變與極性強化。將釔含量1.6 a.t.%的薄膜與純氧化鋅薄膜用於製作元件後，得到的輸出電壓、電流分別為0.012 V、45 nA與0.002 V、25nA，結果可發現不論是在輸出電壓或是輸出電流的表現上，釔摻雜氧化鋅薄膜之表現均優於純氧化鋅薄膜，且具備發展潛能。未來透過對薄膜加工處理及元件設計優化後，能再提升其輸出表現，並結合壓電電子、壓電光電子等效應後擴大應用範圍。

Wurtzite structure materials such as ZnO are considered to be the promising candidate for nanogenerators because of its unique properties. In this paper, we investigate the effect of yttrium(Y) doping on the piezoelectric coefficient of ZnO thin films synthesized on p-type Si (111) substrates via RF magnetron sputtering. XRD diffraction patterns show that all films presented ZnO wurtzite structure with c-axis preferential orientation and high crystallinity under small amount of yttrium doping. The chemical binding energy and composition of the thin films are measured by XPS, and the results confirm the substitution of zinc by yttrium. The electric hysteresis loop exhibits the ferroelectric property of Y doped ZnO thin films, which is the key to the enhancement of piezoelectric properties. The measurement of piezoelectric coefficient (d33) by PFM showing that Y doped ZnO thin films reach 49.6 pm/V at yttrium concentration is 1.6 a.t.%, which is higher than d33 of pure ZnO thin films. The Y doped ZnO based-nanogenetors present better output performance than that of ZnO based-nanogenerators, so it is considered that Y doped ZnO thin films have more potential to be developed on the field of nanogenerators.

摘要 I
Extended Abstract III
致謝 XXI
總目錄 XXIII
表目錄 XXVI
圖目錄 XXVII
第一章、緒論 1
1.1. 前言 1
1.2. 研究動機與目的 3
第二章、文獻回顧 4
2.1. 濺鍍系統 4
2.1.1 濺鍍原理 4
2.1.2 射頻磁控濺鍍 9
2.2. 氧化鋅性質 11
2.2.1. 晶體結構 11
2.2.2. 物理性質 14
2.2.3. 本質缺陷 16
2.3. 壓電效應 21
2.3.1. 壓電材料 21
2.3.2. 壓電性 22
2.3.3. 鐵電性 24
2.3.4. 壓電電位與壓電極化 26
2.4. 釔摻雜氧化鋅 30
2.5. 壓電型奈米發電機 32
2.5.1. 永續能源之議題 32
2.5.2. 奈米發電機之原理及應用 35
第三章、研究方法與實驗步驟 40
3.1. 實驗流程圖 40
3.2. 實驗材料 41
3.3. 實驗設備 41
3.4. 濺鍍的步驟與條件 42
3.4.1. 基板前處理 42
3.4.2. 濺鍍流程 42
3.4.3. 元件製作 42
3.5. 薄膜性質分析與元件量測 45
3.5.1. 元素成分與化學鍵結分析 45
3.5.2. 晶體結構分析 45
3.5.3. 表面形貌與微結構分析 46
3.5.4. 電滯曲線分析 47
3.5.5. 壓電係數分析 47
3.5.6. 元件量測 47
第四章、實驗結果與討論 48
4.1. 元素成分與化學鍵結分析 48
4.2. 晶體結構分析 54
4.3. 表面形貌與微結構分析 57
4.4. 電滯曲線分析 62
4.5. 壓電係數分析 64
4.6. 元件量測 69
第五章、結論 76
參考文獻 78

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