Donor-Acceptor Polymer Systems for Electrical Memory Device Applications
Date Issued
2013
Date
2013
Author(s)
Yu, An-Dih
Abstract
Organic-based memory devices have received extensive scientific interest due to their advantages of flexibility, scalability, and material variety. However, the relationships between molecular structures, donor/acceptor compositions and electrical memory characteristics have not been fully explored yet. In this thesis, several donor/acceptor polymeric systems were explored for the understanding of structural or composition effects on the electrical characteristics of resistor-type and transistor-type memory devices. Additionally, the stability of the flexible memory devices was also examined in both memory types for the development of next-generation electronics.
In the first three parts of this thesis, materials for resistor-type memory application were investigated. In chapter 2, triphenylamine–pyrene containing donor–acceptor (D-A) polyimides (PIs) on flexible poly(ethylene naphthalate) (PEN)/Al/PIs/Al cross-point devices were developed, which showed the memory characteristics changing from volatile to nonvolatile via the relative copolymer ratio. The PIs were prepared from the diamines AMTPA or pyrene-contained APAP and the dianhydride 6FDA, with relative AMTPA/APAP molar compositions of 100/0, 95/5, 90/10 and 0/100. As the APAP content increased, the memory device characteristics changed from volatile to nonvolatile behavior of flash and write once read many (WORM), since the pyrene moiety could stabilize the radical cation of the APAP moieties. In chapter 3, the PIs blended films were prepared from different compositions of PI(AMTPA-6FDA) and polycyclic aromatic compounds (p-type coronene or n-type PDI-DO). The additives of large π-conjugated polycyclic compounds stabilized the charge transfer complex induced by the applied electric field. Thus, the memory device characteristic changed from the volatile to nonvolatile behavior of flash and WORM as the additive contents increased in both blend systems. Due to the stronger accepting ability and higher electron affinity of PDI-DO than those of coronene, the PI(AMTPA):PDI-DO blend based memory devices showed a smaller threshold voltage and changed the memory behavior in a smaller additive content. Additionally, the endurance and bending cyclic measurements confirmed that the above flexible PI memory devices exhibited excellent reliability and mechanical stability. In chapter 4, bistable resistive switching characteristics collected from the nanocomposites of block copolymers (BCP) and graphene oxide (GO). A well-dispersed composite was obtained through a simple process of blending that utilizing supramolecular interaction between BCP and GO. Nonvolatile WORM memory characteristics were observed from the BCP:GO-based device. The composite could serve as charge storage material and effectively enhance the conductivity under applied bias.
In the last two parts of this thesis, polymer electrets for transistor-type memory were developed. In chapter 5, memory characteristics of n-type BPE-PTCDI-based OFET using a series of D-A polyimide electrets of PI(AMTPA-6FDA), PI(APAN-6FDA), PI(APAP-6FDA) were studied. Among the polymer electrets, the OFET memory device based on PI(APAP-6FDA) exhibited the largest memory window and the best charge retention ability due to the introduction of polycyclic arene pyrene into the electron donating moiety. With the excellent carrier delocalization, pyrene successfully enhanced the charge storage ability and sustained the CT complex for high performance nonvolatile OFET memories with electrets of D-A polyimide system. In chapter 6, a series of polyimides (PITE(BMI-BMMD), PI(APS-ODPA), and PI(APS-BPA)) were prepared for better understanding the function of CT complex in polymer electret for OFET memory. The memory characteristic changed from the WORM behavior (PITE(BMI-BMMD)) to flash (PI(APS-ODPA) and PI(APS-BPA)), due to the energetic relationships and charge transfer complex. Besides, BPE-PTCDI transistor memory devices fabricated on flexible PET substrates exhibited multilevel data storage (WMRM) characteristics since the dielectric capacity was enhanced by its high sulfur-content of PITE(BMI-BMMD). Such flexible WMRM devices could have potential applications for the next generation high-density data storage components.
Subjects
電阻式記憶體
電晶體式記憶體
高分子複合物
施體-受體聚醯亞胺
可撓曲記憶體
Type
thesis
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