以NEXAFS和AFM對五環素分子在經刷膜處理十八烷基三氯矽烷薄膜分子位向取向之研究

Abstract

本論文可分為三部份，第一部份使用原子力顯微技術、同步輻射光X光電子能譜與近緣X光吸收細微結構光譜研究十八烷基三氯矽烷（n-octadecyltrichlorosilane）在矽(100)基材的自組裝薄膜系統，探討在不同製備條件下分子薄膜表面形貌、薄膜化學組成與表面分子排列取向的變化。我們亦透過機械刷膜方式來試圖改變表面形貌與分子排列取向，實驗結果顯示十八烷基三氯矽烷分子可透過刷膜方式來改變其表面形貌與分子排列傾角，但並無特定排列方向，在不同成長條件下刷膜影響到X光電子能譜結果。對於另一分子4-phenylbutyltrichlorosilane也是利用同樣的技術來了解刷膜對於自組裝薄膜的影響。 第二部分研究的系統為在超高真空環境下蒸鍍五環素分子於自組裝薄膜上，研究以不同處理條件下的OTS薄膜（刷膜與無刷膜）對五環素薄膜的表面形貌與分子位向取向的影響。結果顯示五環素薄膜的表面形貌與OTS是否經過刷膜處理有相當大的關係。在未經刷膜處理的OTS薄膜基材上，五環素分子以獨立堆疊方式成長為山丘狀形貌。在經刷膜處理的OTS薄膜基材上，五環素分子以層狀排列成長高原狀的表面形貌。並且研究五環素分子的位向取向也與薄膜的厚度是否有密切的關係。 最後一部分，我們以對五環素薄膜與自組裝OTS薄膜的瞭解作為基礎，試作有機場效電晶體。經由量測場效電晶體的閘極電壓與電流關係結果可得出五環素薄膜的電洞傳導率。明顯地，以刷過的OTS薄膜為基材所製作出的五環素薄膜的電洞傳導率高3個數量級(未經刷膜處理薄膜基材五環素電洞傳導率6.35×10-5 cm2V-1s-1；經刷膜處理薄膜基材五環素電洞傳導率6.15×10-2 cm2V-1s-1)與五環素表面形貌缺陷多寡息息相關。

The present thesis is divided into three parts. The first part discusses using AFM, XPS and NESAFS to study the self-assembled molecular films of n-octadecyltrichlorosilane (OTS) on oxidized Si(100). The employed techniques provide the information about the morphology, electronic structure and molecular orientation of OTS thin films. We also studied how the morphology and molecular orientation of OTS thin films could be modified by rubbing. The result shows that the morphology and tilt angle of carbon chain of OTS can be changed by rubbing. However, no conclusive evidence of molecular alignment along a particular azimuth owing to the rubbing action can be found from azimuthal angle dependence NEXAFS scan. XPS data are also found to be useful in gauging the radiation damage in OTS films associated with prolonged data acquisition. In the same way, we also studied the possible molecular alignment effect induced by rubbing on 4-phenylbutyltrichlorosilane (4-PBTS) SAMs. In the second part, we report on the pentacene thin films vacuum-deposited on the OTS films prepared under different conditions that include monolayer and multilayer respectively treated with and without rubbing. The morphologies of pentacene thin films are found to be sensitively dependent on the substrate condition. The AFM imaging reveals a hill-like growth of pentacene on the unrubbed OTS and a tabletop growth of pentacene on the rubbed OTS. Moreover, the NEXAFS data indicate that the tilt angle of pentacene molecules evolves with the pentacene film thickness. In the last part, we present the fabrication of organic field effect transistor (OFET) based on the information gained from studying pentacene thin films on the OTS. The mobility of pentacene was obtained by evaluating the OFET characteristics containing how the drain current varies with source-drain bias voltage at various set of gate voltage. Pentacene mobility grown on the rubbed-OTS substrate is significantly higher by three-order-of-magnitude than that on the unrubbed-OTS substrate. (6.35×10-5 vs. 6.15×10-2 cm2V-1s-1). The mobility data seem to bear some relationship with the morphology of pentacene.