電荷轉移型超分子駐極體應用於光響應電晶體式記憶體

Application of Charge-Transfer Supramolecular Electret in Photoresponsive Field-Effect Transistor Type Memory

楊芸芳(Yun-Fang Yang)

指導教授 ： 陳文章

國立臺灣大學/工學院/化學工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202102490

摘要

有機光電元件中的易加工和多樣兼容性，促使新興記憶體技術在微縮、高儲存密度和低耗能操作方面上能有所突破並蓬勃發展。其中，電晶體式記憶體基於傳統場效應電晶體的效益和架構是近來備受重視的架構之一，其額外的儲存駐極體層基本上可分為鐵電性介電質、奈米浮動柵極電極、及高分子電荷捕捉材料等。然而，多數電荷儲存層的製備過程中所需複雜的合成路徑抑或精密準確的混摻系統大幅度地增加了元件製備的困難度。為此，超分子藉由材料分子間可逆的非共價鍵結作用力，不僅能形成跨尺度的有序自組裝排列且更能提供一個簡便的製備系統，而富具潛力與應用性，目前卻尚未被探討其於光感式記憶體中的效應。在本論文研究中，我們首先探討一光敏性高分子用於光記憶體電賀儲存層上的記憶體特性，並藉由形成一系列電荷轉移型超分子來改變記憶體的相關行為。此外，我們更進一步合成一系列同感光型嵌段高分子用以闡述相關形貌對光記憶體性能的影響。其研究細節分述如下：
第二章中，為了說明電荷轉移駐極體在電晶體型光記憶體上的影響，我們探討一系列由聚(1-芘甲基丙烯酸甲酯) (PPyMA) 和7,7,8,8-四氰基醌二甲烷 (TCNQ) 所構成之新穎電荷轉移超分子在元件效能上的展現。從結果得知，純PPyMA所形成之記憶體展現出光誘導恢復行為，然而由等含量的光敏性芘和 TCNQ 所組成的電荷轉移型超分子駐極體在不同光源的照射下進一步表現出優異的雙穩態記憶體行為。此外，由於芘和TCNQ在薄膜狀態下能有良好的作用力與均勻的分散性，使得元件能展現絕佳的記憶體表徵。此研究結果不僅證明了電荷轉移型超分子駐極體在光電元件中的良好表現，而且能更進一步拓展自組裝嵌段共聚物型超分子駐極體於未來的研究和應用。
於第三章，為了更進一步拓展電荷轉移型超分子的廣泛應用和功能性，我們於此首先探討了記憶體層的奈米結構和記憶體性能之間的關係。延續前章節的基本概念和材料，我們製備一系列新穎本質光敏性嵌段共聚物—聚（1-芘甲基丙烯酸甲酯）-b-聚（環氧乙烷）（PEO-b-PPyMA），並藉由溶劑退火條件的調控來探討此高分子其自組裝形貌於光響應電晶體式記憶體上的性能表現和影響。結果顯示，在綜合條件達到最穩定平衡下所製備的元件能有最佳記憶體性能以及優異的光響應特性。此外，透過 TCNQ 與 PEO-b-PPyMA 中的 PPyMA 嵌段之間的電荷轉移相互作用所形成的超分子，能更進一步提高了元件的電荷捕捉功能和光電記憶窗口，呈現更加優異的元件效能表現。上述結果不僅展示了一種通過基於本徵功能性的嵌段高分子及其相對應超分子的形態控制來實現高性能光電記憶體的新概念，擴展此類材料於光傳感器和神經元元件等光電元件中的應用，也提供了功能性嵌段高分子於未來光電領域研究的無限潛力，更進一步為後續電荷轉移型嵌段共聚高分子的研究應用建立基本的認識與了解。

關鍵字

超分子 ； 電荷轉移 ； 嵌段共聚物 ； 形態學 ； 光感式記憶體元件

並列摘要

Emerging memory technologies coupled with possible scaling-down, increasing data density, and lowering energy operation have fueled the exponential growth of organic optoelectronics owing to their facile compatibility and availability. Benefiting from the conventional field-effect functionalities, the additional chargeable electrets can be essentially categorized into ferroelectrically oriented dipole-dielectrics, nano-floating gate mediums, and polymeric charge trapping materials. Supramolecule features reversible non-covalent interactions between molecules in an organized self-assemble at multiple length scales, has arisen as an ideal avenue to construct a versatile superficial processable system without sophisticated synthetic routes or hybridization procedures in general material systems. However, there are limited studies of the supramolecular applications on photonic field-effect transistor (FET) type memory. In the thesis, we first revealed the effect of the formation of charge-transfer (CT) supramolecules comprising electron-deficient and intrinsic photosensitive electron-rich aromatic molecules on the memory and electrical characteristics of photonic memory devices. In addition, the extended correlations of the morphological properties and the resultant memory performances were further explored based on block copolymers (BCP) with similar pendant photoactive moieties. The details of each topic are summarized as below:
In chapter 2, a novel series of charge transfer (CT)-based supramolecular electrets comprising poly(1-pyrenemethyl methacrylate) (PPyMA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) was used to elucidate the effect of CT on photonic FET-type memory. The memory devices based on pure PPyMA showed a photo-induced recovery behavior, while the supramolecular electret with an equimolar content of pyrene and TCNQ exhibited superior bistable memory switchability under electrical/photoprograming with UV (365 nm) and green lights (525 nm) illumination. The optimized memory devices based on the CT-electrets with equimolar contents of pyrene and TCNQ exhibited high fault-tolerance and non-volatile characteristics associated with broad memory windows and high memory ratios of over 106 after 104 s. Moreover, the memory endurance test with 100 continuous switching cycles demonstrated superior memory discernibility. The above results not only provide a shred of evidence for CT-based supramolecular electrets warranting applications in optoelectronics but further broaden future investigations in self-assembled block copolymer-based supramolecular electrets.
In chapter 3, an innovative self-assembled BCP-based electret containing pendant photoactive pyrene groups along with their CTsupramolecules was proposed for photonic FET-based memory. The intrinsic photosensitive BCP-based electret consisted of poly(1-pyrenemethyl methacrylate)-block-poly(ethylene oxide) (PEO-b-PPyMA) was used to elucidate the effect of functional polymers incorporated with the morphological issue on photonic FET memory. The superior device, constructed with favorable association and homogeneity in well-ordered hexagonal cylinders through solvent annealing, showed an ultrafast photoresponsive characteristic. Furthermore, the charge-trapping functionality and photoelectrical memory window of the device were further improved through the supramolecules of charge-transfer interaction between the TCNQ and the PPyMA moieties in PEO-b-PPyMA for enhancing the electron-trapping ability. The optimized device using the sphere of the supramolecule electret exhibited the excellent memory characteristics of a wide memory window (52V). Our results revealed a new approach to achieve a high-performance photonic FET memory through the morphology control of intrinsic functionalized-based BCP and their supramolecules. It further expanded the applications of the studied materials in optoelectronic devices, such as photosensor and synaptic devices. Also, it provided a judicious design concept of intrinsic functionalized BCP for future development in the photovoltaic field, and established a general understanding for the potential exploration in CT supramolecular-BCP-based applications.

並列關鍵字

supramolecule ； charge transfer ； block copolymer ； nanostructure ； bistable photomemory

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