以自我組裝單分子層技術選擇性成長之創新製程用以合成碳奈米管圖案

Abstract

有效的選擇性控制碳奈米管成長的位置對其未來的應用是重要的課題之一。本研究,以自我組裝單分子層(SAMs)及Fe金屬輔助成長碳奈米管(CNTs)技術，將提出一個控制碳奈米管選區成長的創新製程。首先以低壓化學氣相沉積法與微影蝕刻技術製備出非晶質矽/氮化矽(a:Si/Si3N4)構成的圖案做為基材以成長SAMs。這些從APTMS 溶液 (N - (2 - aminoethyl) – 3 - aminopropyltrimethoxsilane)沉積的SAMs，其選擇性是基於分子層前端官能基反應性與a:Si作用會大於與Si3N4的作用。在圖案上之SAMs佔有的面積，將首先會用其分子層末端官能基乙二胺，鉗合住鐵離子。接著利用鈉硼化物將鐵離子固化成氫氧化鐵，形成氫氧化鐵圖案。接著氫氧化鐵圖案利用微波電漿化學氣相沉積(MPCVD)系統，先經氫電漿前處理還原為分佈均勻的奈米鐵粒子，然後以鐵粒子當觸媒沉積碳奈米管，形成碳奈米管圖案。在製程中間的產物，包括SAMs、氫氧化鐵和CNTs，利用下列技術評估其特性：接觸角量測、掃描式電子顯微技術(SEM)、AFM、Raman、TXRF、XPS、Auger、穿透式電子顯微技術(TEM)、高解析穿透式電子顯微技術(HRTEM)等等。實驗結果顯示最主要的製程參數包括a:Si表面之活化製程及其氣氛，鐵離子固化時間及溫度，和氫電漿前處理。製程中毎一步驟之作用將於文中討論。

The well controllable selective growth of carbon nanotubes (CNTs) on the desired area is an important issue for their future applications. In this study, a novel method for selective growth of CNTs was proposed by using the technologies of self-assembled monolayers (SAMs) and the Fe-assisted CNTs growth. The Si wafers with the a:Si/Si3N4 layer patterns were first prepared by low pressure chemical vapor deposition (LPCVD) and lithography techniques to act as the substrates for selective deposition of SAMs. The selectivity of SAMs from APTMS solution (N-(2-aminoethyl)-3-aminopropyltrimethoxsilane) is based on its greater reactivity of head group on a:Si than Si3N4 films. The areas of pattern with SAMs will first chelate the Fe3+ ions by their diamine-terminated group. The Fe3+ ions were then consolidated to become Fe-hydroxides in sodium boron hydride solution to form the Fe-hydroxides pattern. Finally, the Fe-hydroxides pattern was pretreated in H plasma to become a well-distributed Fe nano-particles on the surface, and followed by CNTs deposition using Fe as catalyst in a microwave plasma-chemical vapor deposition (MP-CVD) system to become the CNTs pattern. The products in each processing step, including SAMs, Fe-hydroxides and CNTs, were characterized by contact angle measurements, scanning electron microscopy (SEM), Raman, XPS, Auger spectroscopy, transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The results show that the main process parameters include the surface activation process and its atmosphere, consolidation time and temperature, H plasma pretreatment. The function of each processing step will be discussed.