The Structure and Electro-optical Properties of ZnO:Fe Thin Film by RF Magnetron Sputtering
廖志偉、王立民 ; 宋皇輝
E-mail: [email protected]
ABSTRACT
ZnO：Fe films were grown by the RF magnetrom sputtering technique. In this work we studied the influences of crystalline
substrates, surface morphology and doping concentration on the conductivity、carrier concentration、mobility、transmittance and magnetization. The sputtering parameters were adjusted and employed to obtain the optimum electro-optical properties of ZnO
：Fe thin film. The optimum conditions for the growth of 150-nm ZnO：Fe films are set with ZnO RF power = 30 W、Fe RF power = 10 W、working pressure = 1 mTorr、growth temperature = 450 oC. As a result of this work, we have successfully achieved the lowest resistivity of 1.59×10-2 Ωcm, the carrier concentration of 3.79×1019 m-3 with the mobility of 10.3 cm2/Vs.
The average optical transmittance with in the visible spectra is higher than 90.4 %. It is found that the average visible optical transmittance increases with reduce of the surface roughness. The ZnO：Fe films with the Fe/Zn of 1.153 at.% have the highest conductivity. Moreover, the resistivity is reduced with the increase of the grain size. The hysteresis curve measured at 300K show that ZnO：Fe films exhibit ferromagnetism with the curie temperature higher than 300 K. The saturation magnetization (Ms) increases as the proportion of Fe atom is increased.
Keywords : ZnO ; RF magnetron sputtering ; ZnO：Fe ; resistivity ; doping Table of Contents
目錄 封面內頁 簽名頁 授權書．．．．．．．．．．．．．．．．．．．．．．．．．iii 中文摘要．．．．．．．．．．
．．．．．．．．．．．．．．iv 英文摘要．．．．．．．．．．．．．．．．．．．．．．．．v 誌謝．．．．．．．
．．．．．．．．．．．．．．．．．．．vi 目錄．．．．．．．．．．．．．．．．．．．．．．．．．．vii 圖目錄．
．．．．．．．．．．．．．．．．．．．．．．．．x 表目錄．．．．．．．．．．．．．．．．．．．．．．．．
．xv 第一章 緒論 1.1 透明導電膜之發展．．．．．．．．．．．．．．1 1.2氧化鋅薄膜(zinc oxide thin films，ZnO)的介紹
．．．4 1.3 ZnO摻雜使其導電的研究現況．．．．．．．．．．6 1.4 磁性ZnO的摻雜．．．．．．．．．．．．．．．7 1.5 文獻上磁性ZnO摻雜的實驗結果．．．．．．．．9 1.6 研究動機與目的．．．．．．．．．．．．．．．11 第二章 理 論基礎 2.1 XRD結構分析理論基礎．．．．．．．．．．．．12 2.1.1 布瑞格繞射定律 (Bragg’s law)．．．．．．．12 2.1.2 施瑞爾關係式 (Scherr Equation)．．．．．．13 2.2 晶粒與晶界對片電阻之關係．．．．．．．．．．15 2.3 磁滯曲線
．．．．．．．．．．．．．．．．．．16 第三章 實驗方法與步驟 3.1 實驗流程．．．．．．．．．．．．．．．．．
．18 3.2 實驗材料．．．．．．．．．．．．．．．．．．20 3.2.1 靶材．．．．．．．．．．．．．．．．．．20 3.2.2 基材．．．．．．．．．．．．．．．．．．20 3.3 實驗裝置．．．．．．．．．．．．．．．．．．21 3.4 鍍膜參數及 步驟．．．．．．．．．．．．．．．24 3.4.1 鍍膜參數．．．．．．．．．．．．．．．．24 3.4.2 基座清洗．．．．．
．．．．．．．．．．．24 3.4.3 沉積ZnO：Fe 薄膜．．．．．．．．．．．25 3.5薄膜性質測試與分析．．．．．．．．
．．．．．25 3.5.1 膜厚量測．．．．．．．．．．．．．．．．26 3.5.2 霍爾效應量測．．．．．．．．．．．．．．26 3.5.3 X-Ray 繞射分析．．．．．．．．．．．．．29 3.5.4 光學穿透度量測．．．．．．．．．．．．．30 3.5.5 表面平坦 度量測．．．．．．．．．．．．．31 3.5.6 超導量子干涉磁量儀(Superconducting Quantum Interference Device，SQUID)
．．．．．．．31 3.5.7 X射線能量散佈分析儀 (Energy Dispersive Spectrometer, EDS)．．．．．．．．．．．．33 第四章 結果與討論 4.1 ZnO：Fe薄膜之成長特性與結構之研究．．．．．36 4.1.1 薄膜成長速率之探討．．．．．．．．．．．36 4.1.1(a) 射頻功率之影響．．．．．．．．．．．36 4.1.1(b) 工作壓力之影響．．．．．．．．．．．37 4.1.2 製程參數 對ZnO：Fe薄膜結構之影響．．．41 4.1.2(a) 晶格常數變化之探討．．．．．．．．．41 4.1.2(b) 晶粒大小變化之探討．．
．．．．．．．41 4.1.3 製程參數對ZnO：Fe薄膜原子組成之影響．52 4.1.4 製程參數對ZnO：Fe薄膜表面型態之探討．55 4.1.4(a) ZnO射頻功率之影響．．．．．．．．．55 4.1.4(b)Fe射頻功率之影響．．．．．．．．．．56 4.1.4(c)工作壓力之 影響．．．．．．．．．．．56 4.1.4(d)工作溫度之影響．．．．．．．．．．．57 4.2 製程參數對ZnO：Fe薄膜光電特性 之影響：製程參數最佳化．．．．．．．．．．．．．．．．．．．67 4.2.1 成長溫度對ZnO：Fe薄膜電特性之影響：成 長溫度之決定．．．．．．．．．．．．．．．67 4.2.2 電阻率、載子濃度與遷移率之探討．．．．．70 4.2.3 光穿透率之 探討．．．．．．．．．．．．．74 4.2.4 影響ZnO：Fe薄膜導電性之綜合討論．．．80 4.3 磁性現象．．．．．．．．．
．．．．．．．．．83 第五章 結論．．．．．．．．．．．．．．．．．．．．．．85 參考文獻．．．．．．．．．．
．．．．．．．．．．．．．．86 圖目錄 圖1.1 ZnO六方晶系結構．．．．．．．．．．．．．．．．．6 圖1.2 以理論預 測Mn與Co摻雜ZnO系統其載子濃度對鐵磁相穩定之相依關係．．．．．．．．．．．．．．．．．．．9 圖2.1 布拉格晶 格繞射示意圖．．．．．．．．．．．．．．．14 圖2.2 磁滯曲線圖．．．．．．．．．．．．．．．．．．．．17 圖3.1 實驗流程．．．．．．．．．．．．．．．．．．．．．19 圖3.2 薄膜製程設備．．．．．．．．．．．．．．．．．．
．22 圖3.3 ZnO：Fe 薄膜製備相關位置圖．．．．．．．．．．．．23 圖3.4 α-step 量測方式示意圖．．．．．．．．．
．．．．．．26 圖3.5 典型霍爾量測的配置．．．．．．．．．．．．．．．．28 圖3.6 Hall Effect 量測圖形及量測方式．
．．．．．．．．．．28 圖3.7 X光繞射儀裝置圖．．．．．．．．．．．．．．．．．29 圖3.8 PC量測實驗裝置圖．．
．．．．．．．．．．．．．．．30 圖3.9 超導量子干涉磁量儀儀器裝置．．．．．．．．．．．．33 圖3.10 能量散佈分 析儀裝置，型號：HITACHI S-3000N．．．35 圖4.1 ZnO：Fe薄膜在工作壓力1 mTorr 下，Fe射頻功率10 W，薄膜成長速 率與ZnO射頻功率之關係圖．．．．．．．38 圖4.2 ZnO：Fe薄膜在工作壓力1 mTorr 下，ZnO射頻功率30 W，薄膜成長 速率與Fe射頻功率之關係圖．．．．．．．．39 圖4.3 ZnO：Fe薄膜以不同工作壓力濺鍍之薄膜成長速率圖．．40 圖4.4 工作壓力1 mTorr ，Fe射頻功率10 W， 不同ZnO射頻功率的ZnO：Fe薄膜XRD圖．．．．．．．．．．．．．43 圖4.5 工 作壓力1 mTorr，ZnO射頻功率30 W， 不同Fe射頻功率的ZnO：Fe薄膜XRD圖．．．．．．．．．．．．．．44 圖4.6 Fe 射頻功率10 W，ZnO射頻功率30 W， 不同工作壓力的ZnO：Fe薄膜XRD圖．．．．．．．．．．．．．．．45 圖4.7 工 作壓力1 mTorr ，Fe射頻功率10 W， 不同ZnO射頻功率的ZnO：Fe薄膜c軸方向晶格常數圖．．．．．．．46 圖4.8 工作 壓力1 mTorr ，ZnO射頻功率30 W， 不同Fe射頻功率的ZnO：Fe薄膜c軸方向晶格常數圖．．．．．．．47 圖4.9 Fe射頻 功率10 W，ZnO射頻功率30 W， 不同工作壓力的ZnO：Fe薄膜c軸方向晶格常數圖．．．．．．．．．．48 圖4.10 為ZnO
：Fe薄膜在不同的ZnO射頻功率下濺鍍，所計算的晶粒大小圖．．．．．．．．．．．．．．．．．．．．49 圖4.11 ZnO
：Fe薄膜在不同的Fe射頻功率下濺鍍，所計算的晶粒大小圖．．．．．．．．．．．．．．．．．．．．．．50 圖4.12 ZnO：Fe薄膜在不同的工作壓力下濺鍍，所計算的晶粒大小圖．．．．．．．．．．．．．．．．．．．．．．．51 圖4.13 工作壓力1 mTorr ，Fe射頻功率10 W， 不同ZnO射頻功率所沉積之ZnO：Fe薄膜的Fe/Zn at.%圖．．．．．．．53 圖4.14 工作壓力1 mTorr ，ZnO射頻功率30 W， 不同Fe射頻功率所沉積之ZnO：Fe薄膜的Fe/Zn at.%圖．．．．．．．54 圖4.15 工作壓力1 mTorr 下，Fe射頻功率10 W，ZnO：Fe薄膜在不同的ZnO射頻功率下濺鍍，所沉積之ZnO：Fe薄膜 的AFM表面型態圖．．．．．．．．．．．．．．．．．58 圖4.16 工作壓力1 mTorr 下，Fe射頻功率10 W，ZnO：Fe薄 膜在不同的ZnO射頻功率下濺鍍，所沉積之ZnO：Fe薄膜的AFM表面平整度比較圖．．．．．．．．．．．．．．59 圖4.17 工作壓力1 mTorr 下，ZnO射頻功率30 W，ZnO：Fe薄膜在不同的Fe射頻功率下濺鍍，所沉積之ZnO：Fe薄膜 的AFM表面型態圖．．．．．．．．．．．．．．．．．60 圖4.18 工作壓力1 mTorr 下，ZnO射頻功率30 W，ZnO：Fe 薄膜在不同的Fe射頻功率下濺鍍，所沉積之ZnO：Fe薄膜的AFM表面平整度之比較圖．．．．．．．．．．．．．61 圖4.19 ZnO射頻功率30 W，Fe射頻功率10 W，ZnO：Fe薄膜在不同的工作壓力，所沉積之ZnO：Fe薄膜的AFM表面型態 圖．．．．．．．．．．．．．．．．．．．．．．．．62 圖4.20 ZnO射頻功率30 W，Fe射頻功率10 W，ZnO：Fe薄膜 在不同的工作壓力，所沉積之ZnO：Fe薄膜的AFM表面平整度圖．．．．．．．．．．．．．．．．．．．．．．．63 圖4.21 圖4.21 (a)-(g) 為工作壓力1 mTorr下、ZnO射頻功率30 W、Fe射頻功率10 W，ZnO：Fe薄膜在不同的工作溫度(a)350 oC、(b)400 oC、(c)430 oC、(d)440 oC、(e)450 oC、(f)470 oC、(g)495 oC，所沉積之AFM表面型態圖．．．．．．．．65 圖4.22 工作壓力1 mTorr、ZnO射頻功率30 W、Fe射頻功率10 W下，ZnO：Fe薄膜在不同的工作溫度，所沉積之表面平整 度曲線圖．．．．．．．．．．．．．．．．．．．．．．66 圖4.23 工作壓力1 mTorr，ZnO射頻功率30 W、Fe射頻功 率10 W下，ZnO：Fe薄膜在不同的工作溫度，所沉積之ZnO：Fe薄膜的電阻率作圖．．．．．．．．．．．．．．．．
．68 圖4.24 工作壓力1 mTorr下，ZnO射頻功率30 W，Fe射頻功率10 W，ZnO：Fe薄膜在不同的工作溫度，所沉積之ZnO
：Fe薄膜的晶粒大小對電阻率作圖．．．．．．．．．．69 圖4.25 工作壓力1 mTorr 下，Fe射頻功率10 W，不同ZnO射頻 功率的ZnO：Fe薄膜之電性關係圖．．．．．．．．．71 圖4.26 工作壓力1 mTorr 下，ZnO射頻功率30 W，不同Fe射頻功 率的ZnO：Fe薄膜之電性關係圖．．．．．．．．．72 圖4.27 Fe射頻功率10 W，ZnO射頻功率30 W，不同工作壓力所沉 積之ZnO：Fe薄膜的電性特性圖．．．．．．．．．73 圖4.28 工作壓力1 mTorr 下，Fe射頻功率10 W，不同ZnO射頻功率 的ZnO：Fe薄膜之穿透率曲線圖．．．．．．．．75 圖4.29 工作壓力1 mTorr 下，Fe射頻功率10 W，不同ZnO射頻功率 的ZnO：Fe薄膜之平均穿透率曲線圖．．．．．．76 圖4.30 工作壓力1 mTorr 下，ZnO射頻功率30 W，不同Fe射頻功率 的ZnO：Fe薄膜之平均穿透率曲線圖．．．．．．77 圖4.31 Fe射頻功率10 W，ZnO射頻功率30 W，不同工作壓力所沉積 之ZnO：Fe薄膜的平均穿透率曲線圖．．．．．．78 圖4.32 不同Fe射頻功率與不同工作壓力所沉積之ZnO：Fe薄膜的表面 平整度對平均光穿透率做圖．．．．．．．．．79 圖4.33 ZnO：Fe薄膜在改變射頻功率下濺鍍，所沉積之ZnO：Fe薄膜 的Fe/Zn at.%與電阻率對應圖．．．．．．．．．81 圖4.34 ZnO射頻功率30 W，Fe射頻功率10 W，不同工作壓力下濺鍍
，所沉積之ZnO：Fe薄膜的晶粒大小(D)與電阻率對應圖．．．．．．．．．．．．．．．．．．．．．．．82 圖4.35 ZnO：Fe薄膜300 K所量測的磁滯曲線圖．．．．．．84 表目錄 表1.1 一些目前常用的透明導電物．．．．．．．．．．
．．．1 表3.1 康寧玻璃1737F 之特性．．．．．．．．．．．．．．20 表3.2 鍍膜參數．．．．．．．．．．．．．．．
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