Novel Polyimides Systems for Organic Field-effect Transistor (OFET) Memory Device Applications
Date Issued
2014
Date
2014
Author(s)
Dong, Lei
Abstract
Organic-based memory devices have received extensive research interest due to their advantages of flexibility, solution processability, low cost and materials variety compared to traditional inorganic silicon ones. Meanwhile, polyimide is mostly thought to be one of the best candidates for memory materials, concerning its good thermal stability, chemical resistance and outstanding mechanical strength. However, the relationships between the molecular structures of polyimides and corresponding electrical memory characteristics have not been fully explored yet. In this thesis, both single acceptor and donor/acceptor systems were explored for a better understanding of structural effects on the electrical characteristics of transistor-type memory devices.
In chapter 2, the new semi-conjugated polyimides as the charge-storage electrets for the p-type pentacene-based non-volatile field-effect transistor (OFET) memory devices, comprising different electron-accepting dianhydride moieties, PI(BPDA-DAP), PI(PMDA-DAP), and PI(ODPA-DAP), and varied aliphatic lengths, PI(PMDA-DAH) and PI(PMDA-DAD) were successfully developed. The device fabricated upon PI(BPDA-DAP) electret exhibited the largest memory window owing to its low-lying LUMO energy level resulting from the largest conjugation. Besides, the increment of aliphatic length, from PI(PMDA-DAP) to PI(PMDA-DAH) to PI(PMDA-DAD), led to a gradual switch from flash to WORM (write once read many times) type memory property, accompanied by the reduced memory window. This study demonstrated that the memory characteristics and charge mobility of the transistor memory could be effectively modulated through the adaptation of the electron accepting moiety and spacer moiety in the semi-conjugated polyimide based electrets.
In chapter 3, the nonvolatile memory characteristics of p-type pentacene-based organic field-effect transistor (OFET) using the synthesized polymer electrets PA(BAPF-AC), PI(BAPF-6FDA) and PI(BAPF-ODPA) were systematically studied. These three polymers contain identical electron-donating 9,9-Bis(4-aminophenyl)fluorene (BAPF) and different building blocks of neutral (hexanediamide (AC) ) and electron-accepting (aromatic hexafluoroisopropylidenediphthalimide (6FDA) and oxydiphthalimide (ODPA)), respectively. The OEFT memory characteristic of devices fabricated with these three polymers vary from the EORM (erase once and read many times) behavior (PA(BAPF-AC)) to semi-flash (PI(BAPF-ODPA)), and to flash (PI(BAPF-6FDA)), mainly due to the differences in energy levels and charge transfer effects. Furthermore, the memory device based on PI(BAPF-6FDA) exhibits the largest memory window, which is attributed to the strong electron-trapping facilitated by the induced charge separation effect from hexafluoropropane moiety. Similarly, the larger torsion angle of PI(BAPF-6FDA) results in the more stable charge transfer complex, leading to more electrons trapped. The present study provided an insight into the relationship between the charge transfer effect and the memory characteristic, and revealed the possible tuning strategies on the chemical structure of materials to achieve varied capabilities of storing charges for advanced OFET memory applications.
Subjects
場效電晶體式記憶體
高分子介電層
受體
施體-受體
聚醯亞胺
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-103-R01524092-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):2c47966f127c52cbf47ccd693b10783f