二元催化劑成長碳螺旋線圈及其製程分析探討

Abstract

使用以二元素鐵與錫所組成之催化劑，結合化學氣相沈積法，可以成功生長碳螺旋線圈。催化劑的調配方式可以用酒精作為溶劑，混合醋酸鐵與醋酸錫，稱為溶液催化劑；或者使用電子束蒸鍍機，將鐵薄膜與錫薄膜蒸鍍在試片上，此種調配出的催化劑稱為薄膜催化劑。由溶液催化劑所成長之線圈外徑在100nm∼1100nm，線徑在100nm∼300nm，螺距在100nm∼1400nm；而以薄膜催化劑成長者線圈外徑<600nm，線徑<200nm，螺距<800nm。成長結果已由SEM與TEM檢測。二元成長機制在於使用可以成長碳管的鐵以及促使碳管蜷曲進而形成螺旋狀的線圈。相較於三元成長，其優點是製程簡單，且易於分析其成長模式。另外研究發現催化劑厚度影響碳螺旋線圈生長之平均尺寸與尺寸分佈，因此使用厚度較厚的溶液催化劑會成長出尺寸較大之碳螺旋線圈。 本文還研究以微機電製程製作出微小催化劑區塊，使碳螺旋線圈生長範圍侷限，已得到在催化劑區塊中僅有單根長度超過10微米之碳螺旋線圈。此結果對於往後鑑定以及定位碳螺旋線圈都有相當大的助益。

Using two metal elements, iron and tin, to prepare catalyst and combine chemical vapor deposition (CVD) process can grow carbon coils successfully. There are tow methods to prepare catalyst. One is to mix iron acetate with tin acetate, and use alcohol as solvent to dissolve these two powders. Such a catalyst is called solution catalyst. The other method is to coat iron film and tin film on wafer by e-beam evaporator directly. This catalyst is named thin film catalyst. Coils grown by solution catalyst have coil diameter 100 nm~1100 nm, fiber diameter 100 nm~300 nm, and pitch 100 nm~1400 nm; While by thin film catalyst have coil diameter <600 nm, fiber diameter <200 nm, pitch <800 nm. Results have been observed by SEM and TEM. Iron is the key to grow carbon tubes. Tin makes carbon tubes become spiral shape. Advantages of tow-element growth of carbon coils are that the process is more convenient and it’s easy to analyze the growth model of carbon coils. It has been researched thickness of catalyst is a key point to effect average coil size and it’s range. Using solution catalyst can grow carbon coils which have larger size. Another part of this research is to make small patterns by micro electron mechanics (MEMs) process and let carbon coils grow inside the pattern. Single carbon coil whose length is above 10 μm can be got in the patterned area. This research can help assaying and locating carbon coils.