根據聯合國的研究顯示，在不久的將來會有三十五萬人活在缺水的環境裡。因此開發新的水資源是未來的一個重要課題。地球上的水資源有96.5%存在於海水中，將海水淡化成可飲用的水是解決水資源缺乏的方法之一。為了解決海水淡化成本過高的問題，現今全世界均致力於發展出高效率之海水淡化方法。
在2012年，曾繁根教授的研究團隊提出了一套利用控制奈米孔道中電雙層厚度以阻止離子通過孔道，借以達到海水淡化的方法。與現今產量最大，發展最成熟的逆滲透相比，此方法有較低的耗能。然而他們使用的陽極氧化鋁基板容易在實驗中產生破裂。在半導體工業中，矽基版有許多製作一維結構的方法。金屬輔助化學蝕刻法是其中一種具有步驟簡單且花費較少的方式。
本研究利用金屬輔助化學蝕刻法製作一維多孔矽基版，討論形成的多孔薄膜形貌與使用不同成分比例蝕刻液之間的關係，藉以達到孔隙率佳之薄膜形貌。多孔矽基版披覆一導電層後再由原子層沈積方式沉積一高介電係數之氧化鉿薄膜。此可調控電雙層疊合之海水淡化薄膜，經由使用0.5 M鹽水之擴散測試證明了此薄膜能有效阻擋離子通過。在施加2伏特的電壓時能減少20.95%的梨子擴散通過。另外，不同極性的電壓施加於薄膜時會有不同的阻擋離子效果，推測是由於不同離子擴散速率不同所導致的現象。此薄膜能夠穩定的運作超過60小時。顯示此薄膜有製作成可攜帶式鹽水淡化裝置的潛力。

Based on the research data from United Nations, there will be more than 2.5 million people live with shortage of fresh water resource in the near future. How to find sufficient water resource is big issue that attracts much attention. Seawater, the biggest (96.5 %) water reservoir on the earth. It seems that desalination provides a good ways to generating fresh water for solving this problem. In nowadays, researchers do lots of efforts that trying to develop new techniques that producing pure water much more efficiently.
In 2012, Prof. Tseng’s groups in NTHU announce a new desalination technical approach. They control the electrostatic charges attracted on the surface of nanochannels, leading the electrical double layer (EDL) being overlapped inside the pores of membrane to blocked ions pass through. However, the anode aluminum oxide (AAO) templates they use as membranes have poor mechanical property which might make its be broken once being at higher flowing/ pressure conditions. On the other hands, silicon is one of possible candidates that are well developed in semiconductor industry. One can fabricate 1D-nanostrucres (e.g. nanowire/nanorod arrays, porous-like structures) on Si wafers by using metal-assisted chemical etching (MACE), which has advantages of low cost and simple manufacturing.
In this study, fabrication of porous silicon templates with pores through whole wafer by MAC etching was performed. Several compositions (HF/H2O2) of etching solutions were examined for optimizing the morphologies of porous structures. Also, the atomic layer deposition (ALD) technique was used for depositing HfO2, a high dielectric strength material coated on porous channels for the applications of seawater desalination. The deionization properties of as-formed membranes with different bias were examined. The ions concentration was most reduced by 20.95 % using 2V applied bias. In fact, the deionized abilities of membranes were different by applying positive or negative bias due to the natural difference between cations and anions. These as-formed membranes can be continuously in operation without loss its deionized ability for 60 hrs. These Si-based deionized membranes assembly show potentials for application in future mobile desalination cells.

ABSTRACT I
摘要 II
致謝 III
TABLE OF CONTENT IV
LIST OF TABLE VI
LIST OF FIGURE VI.
INTRODUCTION 1
1.1. BACKGROUND 1
1.2. MOTIVATION 2
2.LITERATURE REVIEW 3
2.1. DESALINATION METHOD 3
2.1.1. History and methods 3
2.1.2. Reverse Osmosis 6
2.1.3. Electrodialysis 9
2.1.4. Comparison: merits and demerits 11
2.2. METAL-ASSISTED CHEMICAL ETCHING 12
2.2.1. History and Theory 13
2.2.2. Review of papers 17
2.3. THEORY: THE FORMATION OF ELECTRICAL DOUBLE LAYER 24
3.INSTRUMENTS AND EXPERIMENTAL DESIGN 29
3.1. EQUIPMENT 29
3.2. EXPERIMENTAL DESIGN 37
4.FABRICATION OF POROUS SILICON TEMPLATES 39
4.1. EXPERIMENTAL 39
4.2. FORMATION OF AU NP ARRAYS 40
4.3. RESULT FOR HEAVILY P-TYPE DOPED SILICON 42
4.4. RESULT FOR P-TYPE DOPED SILICON 49
4.5. MEMBRANE FABRICATION 56
5.DESALINATION 60
5.1. EXPERIMENT PROCEDURE 60
5.2. RESULT AND DISCUSSION 62
6.CONCLUSION 66
7.FUTURE WORKS 68
8.REFERENCE 69

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