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標題: | 超分子型嵌段共聚物與富勒烯衍生物複合材料於電阻式記憶體之應用 Supramolecular block copolymers: PCBM composite for resistor-type memory device application |
作者: | Shiang-Lin Lian 連翔琳 |
指導教授: | 陳文章(Wen-Chang Chen) |
關鍵字: | 高分子記憶體,阻抗式記憶體,雙嵌段共聚高分子,奈米碳球,超分子吸引力, polymer memory,resistor-type memory,block copolymer,PCBM,supramolecular interaction, |
出版年 : | 2011 |
學位: | 碩士 |
摘要: | 近幾年來,高分子材料應用在記憶體是一個新興的領域。而具有電子施體和電子受體的高分子材料,由於它們可透過分子結構的設計來調控元件的光電性質,因此在高分子記憶體元件應用上吸引了廣泛的研究與討論。然而,關於不同純共聚高分子結構以及奈米複合材料中利用功能性高分子透過特殊物理吸引力以分散、控制富勒烯衍生複合物的大小對高分子記憶體所造成的影響尚未被深入研究。因此,此論文的研究目標著眼於探討具有芴共軛機團硬桿-柔軟嵌段共聚高分子和含有側鏈噻吩共聚嵌段高分子兩類材料隨著不同嵌段比例對純共聚物與奈米複合材料系統對阻抗式高分子記憶體元件性質的影響。
本論文的第一部分(第二章),為探討雙嵌段(不同嵌段長度比例10/37, 10/68)和三嵌段(嵌段長度比例41/40/41)之poly[2,7-(9,9-dihexylfluorene)](PF)-block-poly(2-vinylpyridine)(P2VP)共聚高分子之光電性質、形態學及其記憶體元件應用之結果。在純共聚物系統下PF10-b-P2VP37, PF10-b-P2VP68 and P2VP41-b-PF40-b-P2VP41 其記憶體元件分別展現出靜態隨機讀取記憶體(SRAM), 靜態隨機讀取記憶體(SRAM), 和動態隨機讀取記憶體(DRAM)的元件特性。這三個純共聚物高分子記憶體元件都展現了很高的電流開關比(ON/OFF ratio)(107)和臨限電壓(threshold voltage)大約為-4V左右。這個電性上的開關現象是由於共聚物材料上同時具有芴的部分有自發性傳遞電洞的能力以及具有P2VP當做電洞捕捉陷阱所造成的。至於揮發性的記憶體表現型態主要是由於電洞由電洞捕捉陷阱脫離以及電洞陷阱深度很淺所造成的。另一方面,對於複材系統,藉由混摻不同比例的PCBM到PF-b-P2VP中,其元件分別可以表現出揮發性、一次寫入多次讀取(WORM)或類似導體(consuctor)的行為。而吸收及放光光譜圖譜的結果顯示,共聚高分子PF-b-P2VP與PCBM間會發生電荷轉移,導致元件以此複合材料為主動層的元件會有記憶體性質的表現。然而,元件呈非揮發性質記憶體表現與PCBM本身的電子親和力高有關。研究結果顯示透過混摻不同比例的PCBM或透過分子結構的設計可以用來調控記憶體元件的表現。 本論文的第二部分(第三章),為探討以超分子的方式使用在含有側鏈噻吩共聚嵌段高分子(PT-b-P2VP)及PCBM複合材料應用在高分子記憶體元件的應用。藉由吸收與放光光譜的結果顯示在PCBM與共聚物PT-b-P2VP間有電荷轉移的產生。而以此材料為主動層的記憶體元件表現出一寫多讀的記憶體特性(WORM),它的臨限電壓(threshold voltage)大約在-4~-4.6V而電流開關比(ON/OFF ratio)大約是103 ~105。這個記憶體現象,在低導電態電子注入的機制為熱載子發射(thermal emission),由低導電態轉變為高導電態是由於電荷轉移,而高導電態則可以以電場引導電荷傳遞來解釋。這個研究結果提供了透過功能性雙嵌共聚高分子藉由物理性吸引力來控制富勒烯衍生複合物大小在奈米材料高分子元件記憶體元件上嶄新的應用。 Recently years, polymeric materials use to the memory device applications as an emerging area. The donor-acceptor type polymers have attracted a significant interest for memory device applications due to their tunable electronic properties through molecular design. However, the effects of the different polymer structure on the pure polymer memory characteristics and the application of functional block copolymer composites being used to disperse and control fullerene domain size through specified physical interaction on the nanomaterials composite memory characteristics have not yet been explored. In this thesis, we explore fluorene-based conjugated rod-coil block copolymer and thiophene-containing side-chain polymers with the different block ratio effect of pure copolymer and nanocomposites on resistive type memory device application. In the first part of this thesis (chapter 2), the optoelectronic, morphology and the memory device properties of diblock (with two different ratio 10/37, 10/68) and triblock (with the ratio41/40/41) poly[2,7-(9,9-dihexylfluorene)](PF)-block-poly(2-vinylpyridine)(P2VP) copolymers are reported. The pure copolymer PF10-b-P2VP37, PF10-b-P2VP68 and P2VP41-b-PF40-b-P2VP41 device exhibit SRAM, SRAM, and DRAM characteristic, respectively. The three pure polymers device exhibit high ON/OFF ratio (107) and threshold voltage about -4V. The switching effect is based on the fluorene moieties transport ability with coexisting P2VP as the charge trap sites. The electric volatile is attributed to the back transferring of shallow trap depth. For the composite system, the varied PCBM content of PCBM: PF-b-P2VP composite device exhibit volatile memory behavior, WORM, or conductor behaviors. The optical absorption and photoluminescence indicated the charge transfer between copolymer and PCBM, which lead to memory characteristics. However, the non-volatile type memory characteristic is associated with the high electron affinity of PCBM. We also compare the memory behavior with different block length and the difference between diblock and triblock copolymer. In the case of PCBM: diblock copolymer composite, by loading less content of PCBM in PF10-b-P2VP68 matrix could achieve the memory performances which need loading more PCBM content for PF10-b-P2VP37. This results is due to the longer P2VP block length of PF10-b-P2VP68, it probably attract more amount PCBM approach copolymer, thus, the distance of isolated domain size in the electrical connected channel between two electrodes is decrease. The morphology and the photoluminescence quenching relativity of these two diblock composites also agree with this result. In addition, the triblock: PCBM composite devices have significant lower threshold voltage than diblock: PCBM composite. It is due to the P2VP41-b-PF40-b-P2VP41 have higher π-π interchain stacking and stack together favorably leading the charge transfer between P2VP41-b-PF40-b-P2VP41 and PCBM is probably easier than diblock composite. This study indicate that the device electrical characteristic could be tune by varied the loading PCBM content or the design of copolymer architecture. In the second part of this thesis (chapter 3), supramolecular composite thin films of thiophene-containing side-chain polymers PT-b-P2VP: [6,6]-Phenyl-C61-Butyric Acid Methyl Ester (PCBM) were prepare for memory device. The optical absorption and photoluminescence results indicate that the formation charge transfer between PT-b-P2VP and PCBM. The memory device exhibited the WORM type characteristics with threshold voltage -4 ~ -4.6 and ON/OFF ratio 103 ~105. The switching behavior can be explained by the charge injection dominated thermal emission for OFF state and the field induced charge transport in the ON state. This study provide the novel nanomaterials memory device application through the physical interaction between functional block copolymer and fullerene controlling domain size. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/29185 |
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