密度控制之奈米碳管其成長與特性研究

Abstract

本研究利用高溫爐管於氬氣的氣氛下，成長出特殊形體的章魚狀奈米結構物。而後藉由此奈米結構物，在偏壓輔助微波電漿化學氣相沈積法下成長非連續膜分佈之奈米碳管，以得到不同密度之奈米碳管。 利用掃瞄式電子顯微鏡與穿透式電子顯微鏡分析章魚狀奈米結構物下，我們得知其頭部部分由金、鎳、矽及氧這幾種元素混和而成，而其腳部部分則由非晶質之氧化矽所組成，其頭部顆粒之大小約為300奈米。由掃瞄式電子顯微鏡的觀察發現，章魚狀奈米結構物之大小及分佈都很均勻，且穿透式電子顯微鏡和X-光繞射圖形顯示其腳部均為非晶質且均質的奈米線。我們嘗試改變許多熱處理的參數以明瞭章魚狀奈米結構物的成長機制，推測出其成長方式是類似於溶液-液體-固體 (SLS) 的成長模式。 藉由改變章魚狀奈米結構物中的鎳原子百分比，可以成長出不同密度之奈米碳管。我們量測實驗之不同密度的奈米碳管，發現本實驗中最低碳管密度3.3 x 107 cm-2之試片可得到最低的起始電壓(turn-on voltage)為 2.2 V/µm，及最大之增強係數(enhancement factor) 為2386。

In this study, a unique morphology of octopus-like nanostructure was produced in an argon-ambient high temperature furnace. Subsequently, carbon nanotubes (CNTs) with various densities could be grown relating to the octopus-like nanostructure in bias assisted microwave plasma chemical vapor deposition system. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS) of octopus-like nanostructure demonstrated that the head part is mixture of gold, nickel, silicon and oxygen elements and the feet part is amorphous silicon oxide. The alloy-like head part was around 300 nanometers in diameter and SEM images showed great uniformity in size and distribution. TEM observations and electron diffraction analyses revealed that all feet part nanowires are amorphous and homogeneous without any crystalline domains. Various heat treatment parameters were introduced to understand the growth mechanism of octopus-like nanostructure. It indicate that the growth of octopus-like nanostructure is analogous to the solution-liquid-solid (SLS) process. The CNTs could be grown with different density according to the atomic percent of nickel in octopus-like nanostructure. The field emission properties of CNTs with different density were measured. The lowest turn on voltage at 2.2 V/µm and highest enhancement factor at 2386 was obtained from the lowest density of CNTs with density of 3.3 x 107 cm-2.