以奈米壓痕法量測不同催化劑薄膜厚度以成長不同管徑的奈米碳管叢之機械性質

Abstract

近20年來，不論是理論或是實驗研究都一再地證明了奈米碳管有著令人激賞的電子，熱傳以及機械性質。至今，單壁奈米碳管水平奈米碳管以及奈米碳管化合物已經有很多性質被發現並應用於許多地方，例如:奈米尺寸的熱導體，開關，記憶體等電子元件。 我們研究重點在於不同管徑的奈米碳管叢的機械性質。奈米碳管叢尺寸大，成長方式簡便，所以常被應用於微奈米機電元件。也正因為如此，研究奈米碳管叢的整體機械性質，比起單根的奈米碳管更具重要性。 奈米碳管的管徑不論是對於單壁奈米碳管或是多壁奈米碳管研究，都是一個很重要的影響因素，有許多研究都希望能控制這項因素。目前成功的方法有：改變溶液中金屬催化劑的顆粒大小，或者是在特殊的基板上成長奈米碳管，但是這些方法的成本都較高。本研究利用低成本的方式，在矽基板上蒸鍍不同膜厚的鐵催化劑，經過加熱後，形成不同顆粒大小的鐵催化劑，成長不同管徑的奈米碳管。 至於不同管徑以及密度是否會影響奈米碳管叢的整體機械性質，我們在研究中也利用奈米壓印法量測奈米碳管的彈性模數以及硬度，發現管徑越大，機械強度也隨之增加。

Desirable electrical, thermal and mechanical properties of carbonnanotubes(CNTs) have fueled a continually growing of theoretical and experimental studies of CNTs in the last 20 years. To data, many properties of single CNTs, horizontal aligned CNTs, and CNT composites have been reported for special applications: thermal conductor, switches and memories in nanoscale electronic devices. In our research, we focus on the mechanical properties of different diameter of carbon nanotube turf. The wide range of size and large number of carbon nanotube turf grown by chemical vapor deposition are structures for use in microelectronic devices and microelectromechanical systems (MEMS). It is necessary to understand the mechanical properties of carbon nanotube turf rather than a single tube. The diameter of carbon nanotube is an important factor to influence the single-wall carbon nanotube and the multi-walled carbon nanotube on mechanical properties. Many papers reported that the size of catalyst particles and CNTs grown on special template controlling the diameter of carbon nanotubes. But these methods have a higher cost. In order to reduce the cost of fabricating CNTs, we choose different thickness of iron catalyst, which was formed on top of multilayered substrates of Si/SiO2/Al2O3 by e-beam evaporation. After heating, different size of iron catalyst particle depend on thickness of iron catalyst films. Finally, the different diameters of carbon nanotubes were grown by different size of catalyst particle. Do the difference diameters of carbon nanotube influence the behavior of an assemblage of CNTs? We measure the mechanical properties of different diameters of carbon nanotube turf using the nanoindentation. The nanoindentation tests reveal that the large diameter exist stronger mechanical properties.