無論在半導體，光電，生醫以及能源產業，矽奈米線的重要性不可言喻。近年來在製成技術上有很大的進展，如氣液固生長法(VLS)，固液固生長法(SLS)，溶液生長法，氧化層幫助生長法(OAG)，模組幫助生長法，化學氣相沈積法(CVD)等。實際應用矽奈米線的關鍵在於矽奈米線的幾何控制，其包含長度，晶向和大小。但前面所提及的方法，除了CVD法能夠成長出大尺度排列的矽奈米線陣列之外，其餘的均生長出隨機方向的矽奈米線。不過CVD法的矽奈米線直徑取決於金催化劑的大小，直徑分佈範圍從50-250奈米不等。且用催化方法不可避免的需要飽和摻雜物及溫度要大於900度C，阻礙其應用在積體電路工業上的發展(特別是普遍使用金當催化劑這一環，金對於積體電路來說是毒藥)。

在本篇研究中，我們使用無電鍍金屬沈積法(EMD)，一種簡單又方便的方法去生長出具有單晶，整齊排列，大面積特性的矽奈米線。生長出奈米線之後，我們下一步著重於其幾何控制(生長方向，長度和寬度)。我們的實驗成功地生長出不同成長方向的矽奈米線。當使用(100)試片，生長出垂直試片表面的<100>方向矽奈米線;使用(110)試片則生長出同樣具有<100>方向但傾斜的矽奈米線;至於使用(111)試片生長出<111>垂直表面方向和<100>傾斜方向，且<100>方向形成金字塔外觀。因此，<100>是矽奈米線的優選生長方向。

在長度控制方面，我們實驗出矽奈米線的長度跟蝕刻時間呈一線性關係，生長速率大概為1.08 μm / min，比起VLS法快上許多。直徑控制上我們利用田口法，使用較少的實驗次數去得到最佳的參數，導致出一個較窄的直徑分佈及瞭解各實驗參數的影響效果。此外，量測不同晶向試片的場發射性質和拉慢光譜，(100)上的矽奈米線具有最佳的場發射性質，起始電場為1.5 V / μm和 0.1 μA的電流密度。另一方面，(111)上的矽奈米線表現出最大的拉曼強度訊號。最後我們把利用(100)生長出的矽奈米線上半部成功置換成銅奈米線，對於內連接器，電漿光子和生物感測的應用上是可行的。

Owing to the significance of silicon nanowires, many fields including semiconductor, optoelectronic, bio-sensor, and energy resource, the development of fabricating them is in progress, for example, vapor-liquid-solid (VLS) growth 1, solid-liquid-solid (SLS) growth 2, solution-grown process 3, oxide assisted growth (OAG) 4, template-assisted growth, catalytic chemical vapor deposition (CVD) 5, and others 6. In fact, a crucial key of realizing the practical applications based on SiNWs is the geometric control of fabricated SiNWs - including their lengths, orientations, and sizes. Unfortunately most of methods aforementioned result in randomly oriented SiNWs and exceptionally a catalytic chemical CVD process promise a large-scale aligned SiNWs array. Yet, the diameters of the SiNWs fabricated by this method widely range from 50-250 nm mainly determined by the size of gold (Au) catalysts. More critically, SiNWs fabricated by the catalytic processes inevitably contain saturated dopants and the process temperature is usually above 9000C, impeding their implementation in IC industry (in particularly, the most popular catalyst is gold, an extremely lethal impurity for ICs).

As a result, here we employ a electroless metal deposition (EMD) method 7, allowing simple and convenient approach to generate SiNWs of single-crystalline, well-aligned and large area. After synthesizing the SiNWs, the next step focuses on controlling the geometry (growth direction, length, and width). In our research, we successfully fabricate different growth directions of SiNWs. When using (100) wafer, growth direction is <100> and SiNWs are vertical to the substrate. When using (110) wafer, growth direction is <100> and SiNWs are inclined to the substrate. When using (111) wafer, two growth directions are observed, <111>and <100>; one kind of SiNWs are generated vertically to the substrate, anther kinds are slant to the substrate and form pyramid shapes. Therefore, the preferential crystallographic orientation of fabricating SiNWs is <100> direction.

In our experiment, the length of SiNWs which are grown on the (100) wafer shows a linear relationship with the etching time. The growth rate is about 1.08 μm / min. To compare with VLS method, it is really fast. The diameter control of SiNWs is achieved by employing Taguchi method, a powerful tool that uses less experiment times to get the optimal parameters, leading to the capability of controlling the diameter with narrow distribution and comprehension of the influences from all process parameters. Afterwards, we use SiNWs which are grown on different oriented wafer to do the field emission detection and Raman spectroscopy analysis. The SiNWs (generated from (100) wafer) shows the best field emission property with turn-on field of 1.5 V / μm and 0.1 μA. On the other hand, SiNWs (generated from (111) wafer) shows the greatest Raman intensity. Finally, we make the top parts of SiNWs (generated from (100) wafer) successfully displaced to CuNWs directly. It is feasible to apply as interconnection, plasmonic photon, and bio-sensor.

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