氧化鋅奈米線之氫氣電漿後處理

第四章結果與討論

4.3 氧化鋅奈米線電漿處理效應

4.3.2 氧化鋅奈米線之氫氣電漿後處理

a.形貌分析

氫原子量輕，通常氫電漿作用是為做表面改質、清潔，以氫離子與材料

表面產生反應。由圖 4-23 可得知，隨著氫電漿作用時間增加，氧化鋅奈米

線結構並沒有太大的改變，直到作用時間達到5 分鐘時才可清楚地觀察到奈

米線被破壞，因此，氫氣電漿除了對氧化鋅奈米線表面做清潔的作用也逐漸受到蝕刻，造成結構破壞。

圖4-23 氧化鋅奈米線-氫氣電漿處理之 SEM 圖：(a) 0 min；(b) 1 min；(c) 3 min；(d) 5 min

(a) (b)

(c) (d)

b. X-ray 繞射分析

以氫電漿對氧化鋅奈米線作用，隨著時間增加，氧化鋅結構(002)優選方向：34^o處以及其他峰値的強度皆降低，如圖 4-24 所示。對照 FESEM 圖可發現氧化鋅奈米線被破壞，推測是氫離子經由操作功率較強的微波電漿系統，可能在氧化鋅表面產生反應改變了結構以及蝕刻破壞。

圖4-24 氧化鋅奈米線-氫氣電漿處理之 XRD 圖

c. 光激發螢光光譜分析

圖 4-25 中觀察到氧化鋅本身紫外發光 380 nm、氧空缺綠激發光 500~550 nm，經由氫電漿作用後綠激發光處之發光強度產生趨勢性的變化，隨著氫電漿作用時間增加，綠光強度也逐漸提高，可能因為奈米線的氧空缺數量便多。

圖4-25 氧化鋅奈米線-氫氣電漿處理之 PL 光譜圖

d. 場發射特性分析

藉由氫電漿作用，以表面改質與蝕刻的方式使氧化鋅奈米線產生特性變化。由圖4-26 以及表 4-6 可得知，當氫氣電漿作用 1 分鐘時氧化鋅奈米線的起始電場為10.8 V/μm、臨界電流密度為 8×10^-4 A/cm²。氫電漿對氧化鋅奈米線表面做表面清潔的處理，氫電漿可以有效地增加氧化鋅奈米線內的自由電子濃度以及提升導電性[90]，由於微波電漿系統操作功率較高，因此過長的電漿處理時間同樣地會對奈米線結構造成破壞而影響電子傳導。

圖4-26 氧化鋅奈米線-氫氣電漿處理之場發射特性圖

表4-6 氧化鋅奈米線-氫氣電漿處理之起始電場及臨界電流密度 Turn on field

(V/μm)

Critical current density (A/cm²)

圖 4-27 氧化鋅奈米線-氫氣電漿處理之 F-N 特性曲線圖

4.4 氧化鋅奈米線/奈米鑽石薄膜複合結構之氫氣電漿後處理

由前三節之結果可得到，複合結構以及電漿處理皆可有效提升場發射特性，因此最後將其中最佳的參數組合，利用VLS 法成長氧化鋅奈米線於奈

米鑽石薄膜之上，且利用氫電漿對奈米線處理3 分鐘，並將試片做場發射的

量測分析。圖4-28 與圖 4-29 分別為場發射曲線圖以及 F-N 圖，結合兩種提升場發射特性方式所得到起始電場為6.6 V/μm、臨界電流密度為 3.6×10^-4 A/cm²、場增強因子為1951。由結果可知起始電場以及臨界電流密度沒有太大的變化，而場增強因子則提升至1951，比複合結構未經過電漿處理時的 1565 還要高。可見適度對氧化鋅奈米線進行電漿處理，對奈米線表面做清潔處理並提升內部自由電子濃度，可以有助於提升場發射特性。

圖4-28 氧化鋅奈米線/奈米鑽石薄膜-氫氣電漿處理 3 分鐘之場發射特性圖

圖4-29 氧化鋅奈米線/奈米鑽石薄膜-氫氣電漿處理 3 分鐘之 F-N 特性曲線圖

第五章結論與展望

射特性，氫電漿處理 3 分鐘之氧化鋅奈米線的場增強因子可提升至 903。

6. 將複合結構與電漿處理兩種方式組合，所得到的最佳參數為 VLS 成長氧化鋅奈米線/奈米鑽石薄膜複合結構經由氫電漿處理 3 分鐘，起始電場為6.6 V/μm、臨界電流密度為 3.6×10^-4A/cm²、場增強因子為1951。

5.2 未來展望

1. 整理出擁有最佳場發射效率之氧化鋅奈米線參數:長度、線徑、密度、成長方向。

2. 實際應用此氧化鋅奈米線/奈米鑽石薄膜複合結構於場發射式氣體感測器和場發射顯示器。

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在文檔中氧化鋅奈米線/奈米鑽石薄膜複合結構之特性研究 (頁 80-0)

第四章 結果與討論