STM Study of Mixed Hydrocarbon and Fluorinated Alkanethiol Self-Assembled Monolayers on Au(111)

在有機半導體元件 (organic semiconductor devices)中，藉由調整有機層和金屬電極間電荷注入的能量障礙，控制電荷注入(charge injection)是重要的課題。近年來，隨著自組裝單層膜(self-assembled monolayers, SAMs)技術的蓬勃發展，利用有機分子在電極表面形成SAMs可改變電極的特性，像是金屬電極功函數(work function)。以有機發光二極體(organic light-emitting diodes, OLEDs)方面應用為例，藉由調控電極功函數來調整電子電洞的注入速率，使電子電洞對能夠更有效率在放光層再結合(recombination)放光，對提昇元件的放光效率有所助益。們利用掃瞄式穿隧顯微鏡(scanning tunneling microscope, STM)觀察正癸烷硫醇(decanethiol, CH3(CH2)9SH，為減少金屬功函數)和多氟基正癸烷硫醇(fluorinated decanethiol, CF3(CF2)7(CH2)2SH，為增加金屬功函數)混組裝SAMs在金(111)表面形貌偵測。發現隨著調整混組裝比例，表面上觀察到兩種不同對稱排列的晶格結構，進而推斷當飽和烷鏈和氟取代硫醇混組裝在金(111)時為各自形成區塊排列的相分離(phase-segregation)型態。The minimization of the energy barrier at the electrode/organicsnterface is expected to improve significantly the charge injectionfficiency and thus the performance of organic semiconductor devices.uch a barrier is ascribed to the difference between the molecular energyevels (HOMO or LUMO) and the work function of the electrode materials.r. Yu-Tai Tao at Academia Sinica recently demonstrated that the workunction at the interface could be tuned by adjust the ratio of decanethiolnd fluorinated decanethiol (perF) in mixed monolayers on the electrodes.n this thesis study, scanning tunneling microscopy (STM) was employedo unveil whether the molecules form homogeneous or phase-segregatedilms. When the molar ratio of perF to decanethiol was 1:1, STM imagesxhibited predominantly c(4 x 2) of the decanethiol superlattice on Au(111).hen the solution ratio increased to 2:1, the coverage of c(4 x 2) becamemaller. For films prepared from ratios of 4:1 and 9:1, the p(2 x 2)esignated to the perF appeared. However, the domain sizes were smallerhan 0.1 micron. Accordingly, we concluded that decanethiol and perF inhe mixed monolayers were phase-segregated.謝誌 II文摘要 IV文摘要 V目錄 VI目錄 IX目錄 XII 第一章 緒論 1-1 前言 1-2 自組裝單層膜 2-2-1 自組裝單層分子膜結構 2-2-2 自組裝單層分子膜發展簡介 3-2-3 自組裝單分子膜機制 3-2-4 自組裝單層分子膜應用 9-3 掃瞄式穿隧顯微鏡55-57 9-3-1 簡介 9-3-2 穿隧效應 10-3-3 掃瞄式穿隧顯微鏡工作原理 12-3-4 掃瞄式穿隧顯微鏡操作模式60 14-4 單一成分硫醇在金(111)表面晶格結構介紹 15-4-1 ( )R30°晶格結構62 15-4-2 c(4 x 2)晶格結構66 18-4-3 p(2 x 2)晶格結構72 22-5 混合自組裝單層分子薄膜19,36 24-5-1 製備方法 24-5-2 影響混組裝分子膜的實驗因素 25-6 本論文研究目的 29 第二章 實驗部份 30-1 實驗藥品及耗材 30-2 樣品製備 32-2-1 金(111)表面製備 32-2-2 混合組裝單層膜製備 34-2-3 STM掃瞄探針製備方法 35-2-4 分子修飾探針製備 36-3 掃瞄式穿隧顯微鏡(NANOSCOPE ⅢA, VEECO METROLOGY GROUP, SANTA BARBARA, CA) 37 第三章 結果與討論 38-1 金(111)重排結構 38-2 正癸烷硫醇C(4 X 2)結構 40-3 多氟基正癸烷硫醇P(2 X 2)晶格結構 42-4 混組裝單分子膜STM影像 44-4-1 飽和烷硫醇與多氟基硫醇混組裝比例為1 : 1之STM影像 44-4-2 飽和烷硫醇與多氟基硫醇混組裝比例為1 : 2之STM影像 51-4-3 飽和烷硫醇與多氟基硫醇混組裝比例為1 : 4之STM影像 53-4-4 飽和烷硫醇與多氟基硫醇混組裝比例為1 : 9之STM影像 55-4-5 混組裝單分子膜STM圖比較 57-5 各種比例混組裝單分子膜XPS能譜圖 59-6 調控混組裝單分子膜比例之LFM影像 62 第四章 結論 64 第五章 參考文獻 6