臺灣博碩士論文加值系統

高分子記憶體為近來之新興領域，較傳統元件因其本質特型不同而備受矚目；含電子施體與受體之高分子為被廣泛研究之項目，它具有可調控的光電性質和良好的可加工性，因此在元件應用上擁有極佳之應用潛力。本論文主要目的在由實驗合成出電子施體和一系列不同受體所組成的無規共聚高分子，進行記憶體元件的製備與測試。
在本研究第一個部分 (第二章)，利用 Nitroxide-Mediated Radical Polymerization (NMRP)以三苯胺 (triphenylamine)為施體，三種噁唑衍生物為受體的單聚高分子與其無規共聚高分子，包括Poly(4-vinyltriphenylamine-γ-2-phenyl-5- (4-vinylphenyl)1,3,4-oxadiazole) (TPA-A1), Poly(4-vinyltriphenylamine-γ-2-(4-vinyl biphenyl)-5-(4-phenyl)-1,3,4-oxadiazole) (TPA-A2) 和 Poly(4-vinyltriphenylamine- γ-2-(4-vinylbiphenyl)-5-(4-ethoxyphenyl)-1,3,4-oxadiazole) (TPA-A3)等三種，並以此三種不同電子施體與受體比例(分別為 8:2， 5:5，和 2:8)共聚而得九種無規共聚高分子，並藉由氫核磁共振光譜與元素分析鑑定之。所合成高分子之分子量皆在一萬以上且溶於常見的有機溶劑如氯仿、四氫呋喃和氯苯中。由吸收光譜圖可看出此類無規共聚高分子之吸收峰隨著電子受體含量增加而往電子受體單聚高分子位置位移，由光學吸收限計算可得此系列高分子之能隙在3.36 ~ 3.67 電子伏特；而由循環伏安法得到的電化學能隙與光學能隙結果不吻合主因在本研究之高分子皆是在側鏈上有各自分離且電子施體-受體間彼此不參與軌域混成。由螢光光譜的紅移可發現參入不同比例之電子受體可以有效改變發光峰之峰值。電子施體-受體間比例和側鏈結構對高分子的電子和光電性質之影響在本研究中作完整的分析。
本研究第二部分(第三章) 即利用第一部份所合成之單聚高分子和無規共聚高分子製成記憶體元件。此三明治堆疊結構(ITO/polymer/Al)的元件於大氣環境下量測，所有高分子材料系統皆具有非揮發性與可複寫記憶體性質且擁有較低的起始界限電壓為1.5伏特，其電流開/關比值都在104以上。在一萬秒的維持時間測試中，此類共聚高分子皆表現出優良的穩定性。其元件物理機制受燈絲理論與空間電荷極限電流理論影響。在全對數電流-電壓圖分析中，由於共聚高分子中不同的受體比例，在接近元件起始界限電壓時的斜率在2到3.2間。而此斜率範圍說明了受體中易與鋁配位之氮原子易使燈絲生成且主導了開關機制。另外藉由使用低沸點溶劑(四氫呋喃)製備較粗糙的高分子薄膜將使記憶體元件經多次操作後不易關上，進而表現出類似一寫多讀記憶體(WORM)之性質。本研究建立高分子之化學結構、電子結構與型態對元件之關係，而本論文使用之側鏈型電子施體與受體共聚高分子在記憶體元件上之應用上極具發展潛力。

As an emerging area in organic electronics, polymer memories have become an active research topic in recent years, because they are likely to be an alternative or supplementary technology to the conventional memory fabrication Polymer containing electron donor and acceptor is a spectacular research objective due to the tunable optoelectronic properties and better processibility, which leads to great potential on device application. Therefore, this thesis mainly focuses on the synthesis and characterizations of polymers with pendant electron donor and acceptor moiety combined with their applications on memory device.
In the first part of this thesis (Chapter 2), Nitroxide-Mediated Radical Polymerization (NMRP) was applied to synthesize the homopolymers with pendant triphenylamine (TPA as electron donor) or three different oxadiazole derivatives (A1, A2, and A3 as electron acceptor), and also related random copolymers consisting of pendant donor and acceptor moiety, including poly(4-vinyltriphenylamine-γ-2-phenyl-5- (4-vinylphenyl)1,3,4-oxadiazole) (TPA-A1), poly(4-vinyltriphenylamine-γ-2-(4-vinyl- biphenyl)-5-(4-phenyl)-1,3,4-oxadiazole) (TPA-A2), and poly(4-vinyltriphenylamine- γ-2-(4-vinyl biphenyl)-5-(4-ethoxyphenyl)-1,3,4-oxadiazole) (TPA-A3). By changing the donor:acceptor ratio (8:2, 5:5, and 2:8, respectively), nine targeted random copolymers are successfully synthesized and characterized by 1H NMR spectrum and element analysis (EA). All the polymers have number average high molecular weight (>104) with polydispersity index (PDI) of 1.15 ~ 1.45, and soluble in common organic solvents such as chloroform, THF and chlorobenzene (CB). The shifted absorption band of these copolymers were shown as the increasing acceptor content, and the band gaps calculated from absorption edge are in the range of 3.36 ~ 3.67 eV. The poor orbital hybridization between adjacent donor and acceptor moiety, where each pendent group could be considered as an isolated one, causes the deviations between the band gaps obtained from the cyclic voltammetry (CV) and optical spectrum. Furthermore, adding acceptor moiety to copolymers will shift the λmax to longer wavelength in fluorescence spectra. The different side-chain donor/acceptor structures and ratios which influence the electronic and optoelectronic properties were systematically investigated.
In the second part of this thesis (Chapter 3), both synthesized homopolymers and copolymers were used to evaluate the memory applications. The memory device of synthesized polymers with the configuration of ITO/Polymers/Al shows nonvolatile and rewritable switching current-voltage (I-V) characteristics. The turn-on threshold voltage is located around 1.5 V, and the memory device exhibits a high on/off current ratio of 104 and long retention time of 104 second in ambient atmosphere. The mechanism of the switching behavior is based on filamentary conduction with space charge limited current (SCLC) theory. The slope of logarithmic I-V curves enhances from 2 to 3.2 with increasing acceptor content which explains that the presence of the strong coordinate atom (N) on acceptor unit with Al reveals the filament formation behavior. Moreover, the rough polymer thin film surface prepared from low boiling point solvent (THF) shows WORM-like electrical memory switching since it becomes difficult to turn-off during the several cycles. The present study suggested the pendent electron donor and acceptor random copolymers have potential application on memory devices. The relationship between the chemical structure, electronic properties, morphologies and device performance were also established in this study.

摘要 I
Abstract III
Table Captions VII
Figure Captions VIII
Chapter 1、 Introduction 1
1-1 Introduction to Polymeric Memory 1
1-2 Literature Review in Polymeric Memory 3
1-2-1 Mechanism Based on Trapping and Detrapping 4
1-2-2 Mechanism Based on Charge Transfer 6
1-2-3 Mechanism Based on Filament Theory 8
1-2-4 Other Effects 9
1-3 Research Objectives 10
Reference 12
Chapter 2、 Syntheses and Characterization of Side Chain Triphenylamine and Oxadiazole Derivatives Copolymers 17
2-1 Introduction 17
2-1-1 Nitroxide-Mediated Radical Polymerization (NMRP) 18
2-2 Experimental Section 19
2-2-1 Materials 19
2-2-2 Syntheses of Monomers 20
2-2-3 General Procedure of Polymerization 27
2-2-4 Measurements 30
2-3 Polymer Characteristics and Discussion 31
2-3-1 Structure Characterization 31
2-3-2 Thermal Properties 32
2-3-3 Optical Absorption and Photoluminescence Properties 33
2-3-4 Electrochemical Characteristics 35
2-5 Conclusions 36
References 37
Chapter 3、 Memory Device Application for Side Chain Triphenylamine and Oxadiazole Derivatives Copolymers 58
3-1 Introduction 58
3-2 Experimental Section 59
3-2-1 Fabrication 59
3-2-2 Measurement 59
3-3 Results and Discussion 60
3-3-1 Process Issue in Memory Performance 60
3-3-2 Different Acceptors Effect 62
3-3-3 Different Donor-Acceptor ratio Effect 63
3-3-4 Mechanism 65
3-4 Conclusions 67
Reference 68
Chapter 4、 Conclusion and Future Work 90

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