本研究成功利用聚苯乙烯球奈米球微影術(Nanosphere Lithography，NSL)結合金屬催化化學蝕刻法在(100)矽晶圓上成功製備大面積準直規則排列之矽單晶奈米線陣列，此矽晶奈米線陣列的尺寸以及高度可藉由氧氣電漿處理以及濕式蝕刻的時間來妥善調控，完成製備矽晶奈米線後，以無電鍍金屬催化蝕刻法，藉由銀離子的氧化還原反應來修飾矽晶奈米線的樣貌，將平頭矽晶奈米線成功轉變成尖針狀的形貌，並藉由實驗的觀察發現尖針狀的形貌由來是因為疏水性矽晶奈米線頂部的上方以及側壁蝕刻所造成，而後藉由掃描式電子顯微鏡、穿透式電子顯微鏡以及水滴接觸角觀察其尖針化趨勢、形成機制以及尖端變化，並以此成功製備的尖針狀矽晶奈米線以傾斜角鍍膜技術鍍製一層90 nm的鈷金屬於奈米線側壁，進行低溫及高溫長時間的熱退火處理，發現在氮氫氣環境經450℃ 2小時以及650℃~850℃ 4小時的熱退火處理後可獲得鈷金屬原子擴散的尖針狀二矽化鈷/矽異質奈米線結構，此矽化物的區域是呈現(111)鋸齒狀刻面，經過穿透式電子顯微鏡以及選區電子繞射圖譜解析後得知低溫第一矽化物生成相為矽化鈷，但隨著溫度提高使得所生成矽化物均為二矽化鈷。而此研究還針對不同循環蝕刻次數的尖針狀矽晶奈米線以及尖針狀二矽化鈷/矽異質奈米線進行場發射性質量測，探討奈米線尖端曲率以及高深寬比對場發射性質的影響，另外，可假設在奈米線形貌不變的條件下，尖針狀矽晶奈米線以及尖針狀矽/矽化物異質奈米線之場增強因子不會改變，但在矽化反應之後獲得提早啟動的電場以及較低的等效功函數(Effective Work Function)，啟動電場也由原來的 1.30 Vum^(-1)提早至約 0.88 Vum^(-1)而等效功函數由 5.0 eV 下降至 3.7 eV 左右。 ;In this study, we demonstrated that large-area arrays of vertically-aligned single crystalline silicon nanowire were successfully fabricated on (100)Si substrates by using the polystyrene nanosphere lithography combined with the Au-assisted chemical etching process. The diameter and length of these silicon nanowires are adjustable through oxygen plasma treatment and wet etching time. SEM, TEM, SEAD, and contact angle analysis reveal that silicon nanowires that produce on (001)Si substrate have flat ends and their axial orientation is along the [001] direction. The morphology of the silicon nanowires can be converted from flat top to sharp top by metal-catalyzed electroless deposition etching method through the oxidation-reduction of silver. After the process, the silicon nanowires still remain vertically aligned and exhibit a very remarkable tapered geometry. For the Co thin film coated needle-like silicon nanowires samples after annealing at 450℃~850℃ for 2-4hr in N_2/H_2 ambient, needle-like epitaxial CoSi_2/Si heterostructured nanowires were formed. The field emission measurement revealed that the vertical-aligned, needle-like silicon nanowire arrays process excellent field emission properties with low turn-on field, and high β values. The high field enhancement factor can be attributed to high aspect ratio, nanoscale tip and well-controlled spacing between wet etching silicon nanowires. It was also find that the field emission properties of needle-like silicon nanowires were greatly enhanced after the formation of CoSi_2 phase. The turn-on field was reduced 1.30 Vum^(-1) for the needle-like silicon nanowires to around 0.88 Vum^(-1) for the needle-like CoSi_2/Si heterostructured nanowires.
