分子電子學(意即以分子構成電子元件)是目前很受關注的領域之一，因為分子不僅有半導體性質，也有許多不同於金屬的特殊物理性質。Phenacene系列分子為目前較受歡迎的選項之一，因此在本論文中，我們主要針對Phenacene中的9-Phenacene及Br2-picene做研究。我們以低溫、超高真空的掃描穿隧顯微鏡(STM)來研究9-phenacene在銀(111)表面上的附著，本實驗所觀察的曝量從低於一層至形成奈米晶體的厚度都有，並研究各種表面形態及其電子結構之關聯。Br2-picene之研究則是著重在低於一層的曝量，在此情形下Br2-picene會有總計4種的自組裝形式，並且可以以溫度調控之，除此之外，我們也對各個自組裝形式的不同點進行單點的掃描穿隧能譜測量(STS)，並分析其與各種自組裝之關聯性。在分子電子學中，由小單元組成電子元件的技術也是發展重點之一，因此目前有許多研究是關於分子間的同質、異質結合，藉此發展出新分子或是分子元件(如導線)，在本實驗中，我們也成功在金(111)的表面上以蒸鍍後再加熱樣品的方式進行Br2-picene及1,3,5-tris bromophenyl benzene (TBPB)間的異質結合反應。

Molecular electronics is receiving increased attention because of the unique properties of molecules. And phenacenes are popular candidates for this technology. In this thesis, we focus on the properties of 9-phenacene and Br2-picene. Here we study the adsorption of 9-phenacene on a Ag(111) surface. Different coverages ranging from sub-monolayer to nano-crystals are observed with low temperature scanning tunneling microscope (STM) in UHV, each are also correlated with their electronic states.Furthermore, the sub-monolayer adsorption of Br2-picene on Ag(111) is investigated. Four self-assembly configurations are observed and can be tuned by temperature. Their electronic states are also measured by point scanning tunneling spectroscopy (STS). For molecular electronics, the bottom-up construction of parts is also an approach. Therefore the polymerization and hetero-coupling reaction of molecules had been realized on several kinds of molecules. By evaporating molecules onto the surface and further annealing, we succeeded in the hetero-coupling of Br2-picene and 1,3,5-tris bromo phenyl benzene (TBPB) on Au(111).

1 Introduction 7
2 Theory 8
2.1 Tunneling 8
2.1.1 1-dimensional tunneling 8
2.1.2 Landauer theory and Tunneling Conductance 9
2.2 Scanning Tunneling Microscopy 10
2.2.1 Bardeen Theory 10
2.2.2 The mechanism of STM 11
2.3 Scanning Tunneling Spectroscopy 12
3 Instruments 13
3.1 Scanning Tunneling Microscope 13
3.1.1 Chambers 13
3.1.2 Scanner 15
3.1.3 Tip 15
3.2 Ultra High Vacuum 16
3.2.1 The definition of Vacuum 16
3.2.2 The Vacuum system of our STM 17
3.3 Low Temperature Environment 19
3.4 Preparation 19
3.4.1 Ag(111) Crystal 19
3.4.2 Sputter 20
3.4.3 Anneal 21
3.4.4 Evaporation 21
4 9-Phenacene on Ag(111) 22
4.1 9-Phenacene Molecule 22
4.2 Topography 23
4.2.1 0.3 monolayer 23
4.2.2 0.9 monolayer 24
4.2.3 1st monolayer 25
4.2.4 2nd monolayer 25
4.2.5 Islands above the second monolayer 28
4.2.6 Islands on islands 28
4.2.7 Orientations 29
4.3 Electronic states 31
4.3.1 Band gap 31
4.3.2 1st monolayer 31
4.3.3 2nd monolayer 34
4.4 Discussion 36
4.4.1 Topography 36
4.4.2 Electronic states 38
5 Br2-Picene on Ag(111) 39
5.1 Br2-Picene 39
5.2 Topography 41
5.2.1 Overview 41
5.2.2 Characterization 42
5.2.3 Self-assembly structures 45
5.3 Electronic states 49
5.4 Coupling reaction 56
5.4.1 TBPB molecule 56
5.4.2 Picene coupling reaction with TBPB on Au(111) crystal 57
5.5 Discussion 60
5.5.1 Self-assembly of Br2-picene 60
5.5.2 Coupling reaction 62
6 Summary 64

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