銅因為其良好的導電性且價格低廉，除了使用於積體電路中作為導線之外，在奈米線製程可撓曲式透明導電薄膜中也相當具有開發潛力，因此了解銅在奈米尺度下所呈現的性質也日趨重要。雙晶是材料常見的微結構，有文獻指出，若在銅內部導入奈米雙晶結構，不僅能大幅提升銅的機械強度，同時亦可保持良好的導電性。此外，其抗電遷移能力也會有所提升。所以不少研究致力於開發奈米雙晶銅的製程，而本實驗室之前研究成功在自製陽極氧化鋁基板中，以低溫脈衝電鍍製備出高密度竹節狀雙晶結構的奈米線。而關於奈米雙晶銅的化學穩定性方面，文獻指出在材料中雙晶結構的生成會改變晶界結構，進而改善晶界的腐蝕特性，而含有奈米雙晶結構的銅奈米線氧化特性，目前資料則較缺乏。銅奈米線因為表面積與體積比例過大，在應用上需要克服氧化的問題，有研究團隊利用化學法還原鎳層在銅奈米線外形成核殼結構而達到抗氧化的效果，但其實驗多為利用高毒性化學藥劑，不利於一般實驗室使用。
本實驗先以低溫脈衝電鍍出奈米雙晶銅奈米線，並成功開發以低毒性硼氫化鈉還原鎳層形成銅/鎳核殼結構奈米線，利用微製造製程搭配四點探針量測單根奈米線的電阻在不同溫度下隨時間的變化，並分析其氧化特性。高解析度穿透式電子顯微鏡分析竹節狀雙晶的生成；光學量測與顯微鏡元素分析顯示本實驗製程之銅鎳奈米線為核殼結構。電性量測結果則發現含有奈米雙晶結構的銅奈米線，在常溫下可維持其電阻值長達一個月，而銅/鎳核殼結構奈米線在加熱數百小時後其電阻值仍不受影響，證明其有良好的化學穩定性。

Due to it’ s good conductivity and low-cost property, copper (Cu) is often used as interconnect and flexible transparent conductive film material with the introduction of nano-processing. Therefore, many studies try to analyze the properties of copper in nanoscale, such as nanowires (NWs). Twin is a common microstructure in metals. It has been demonstrated that nano-twinned copper have high mechanical strength, good conductivity, and moreover, superior electromigration resistance. In our previous study, we have successfully fabricated Cu NWs with high density of nanoscale traverse twinning structure by using pulsed electrodeposition at low temperature. The formation of nano-twinned structure can also improve the corrosion properties of Cu metallization by changing grain boundary structure. However, research report on the oxidation characteristics of nanotwinned Cu NWs is limited. Copper is prone to oxidation in nanoscale because of high surface-to-volume ratio, some researches showed that Cu-Ni NWs with core-shell structure that was prepared by coating a thin Ni layer on Cu NWs using chemical reduction method possesses good oxidation resistance. Nevertheless, these treatment were mostly done by using highly toxic reducing agent.
In this study, high aspect-ratio nano-twinned Cu NWs were prepared by pulsed current (PC) electroplating, and Cu-Ni core-shell NWs were successfully prepared by the low-toxicity reducing agent, sodium borohydride. Time-and-temperature dependence of electrical resistivity for single Cu and Cu-Ni NWs prepared by micro-fabrication process has been investigated. The bamboo-like twinning structure and core-shell structure of Cu-Ni NWs have been examined by transmission electron microscopy (TEM) and UV-visible/TEM Energy Disperse X-ray analysis. According to four-probe I-V electrical measurement, the resistivity of Cu NWs with nanotwins remained almost constant after exposed in ambient air for one month, while the resistivity of Cu-Ni core-shell NWs also kept unchanged after hundreds hours of thermal aging, revealing good chemical stability.

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