The Effect Of Terminal Groups In Conjugated Organic Molecules To Their Electronic Memory Properties

Since 21 st century, we have entered one information explosion era. The traditional data storage technics have been far behind of the explosive development of information. Traditional data-storage devices based on inorganic materials are close to its bottleneck due to their high production costs, the limited of processing technology, low density data-storage and so on. Hence, more small volume, convenient to carry, easy to use ultra-high density information storage devices is becoming a hot spot of research. The organic electrical storage materials have attracted widely and highly attention of researchers due to the advantages of low processing cost,simple synthesis process, molecular structure design, good mechanical performance, and simple devices preparation process, which is expected to be the first choice of the next generation of high-performance data-storage materials. In this paper, utilizing the structural tailorability of organic materials, we designed and synthesized organic molecular based on carbazole, naphthalene anhydride, indigo and different donor groups. Tuing organic molecules of terminal groups and utilizing multi-mechanism to realize multi-ary information storage research of side chain conjugated polymers. The relationship between the molecular plane Angle, the orientation of organic molecules in the crystal and the sandwich device of electrical conduction and storage behavior were investigated. The research content is divided into the following three aspects:(1) The mechanism of phase transformation and charge transfer regulation and control to realize ternary information storage: two side chain conjugate homo-polymers PCz NIC6 and PNCzNIC6 have been designed and synthesized, and the device were fabricated respectively. The two molecular structure difference in showing the PNCzNIC6 conjugate structure contains strong electron-withdrawing group nitro. Both the current of devices occur mutation from the OFF state first come to ON1 state and switch to ON2 state under constant voltage scanning, the three conducting state shows that the two devices have ternary information storage performance. Based on PCz NIC6 device from the ON2 state will automatically reply to ON1 state after closed voltage, the behavior prove that the device performance is belong to Dynamic Random Access Memory. Whereas PNCz NIC6 devices have remained at the highest conductivity state after reach ON2 state, which is belongs to permanent storage performance(Write Once Read Many times the Memory, WORM). Through to the OFF state and ON1 state film XRD characterization, fluorescence spectra and electron diffraction measurements, proved that the two kinds of material devices from OFF state switch to ON1 state because of the crystalline transition process, which is the process of phase transition. Then ON1 state switching to ON2 state, which is due to the process of charge transfer between the carbazole and naphthalene imide, Because of the weak of electron-withdrawing ability of naphthalene imide, so the formation of charge traps to capture and control electrical ability is weak, thus the PCzNIC6 device turns into the types of DRAM electrical after removal of the electric field. The molecular of PNCzNIC6 has a strong electron-withdrawing group, the ability to capture and control the transferred charge is stronger, after saturation its can keep the device with ON2 state, which show the WORM storage type. So based on these two kinds of material storage devices are two phase change and the charge transfer mechanism of joint control implementation of ternary storage performance. This kind of phase change storage materials will open a new research direction for stable, long-term for the future of multi-band information storage materials research.(2) Investigation of the influence of different heteroatom on molecular plane Angle and device performance. Two molecules ID(BT)2 and ID(BF)2 were designed and synthesized, in which isoindigo acts as electron acceptor and benzoheterocycles act as electron donor at the 6, 6’-position of the isoindigo core. The result illustrated that as the heteroatom in the benzoheterocycle was changed from O to S atom, the intramolecular dihedral angle enlarged from 0.3 to 23°, which led to the ID(BT)2 based device exhibited SRAM memory characteristic and the ID(BF)2 based device exhibited DRAM characteristic. The reason is that the enlarged dihedral angle would prolong the process of the excited electrons in the LUMO side back to the original HOMO side, in other words, the ON state of the ID(BT)2 based device need more time to return to the original OFF state and thus to exhibit SRAM performance, However, ID(BF)2 is almost planarity and has no barrier to impede the excited electrons to recovery to the original state, therefore the ID(BF)2 based device could return back to OFF state from ON state in a very short period of time and exhibited DRAM characteristic. This is a new viewpoint of achieving different type of memory device through changing the steric geometry and improving the intramolecular dihedral angle to impede the charge transferability.(3) Investigation of the influence of different accepter on molecular Crystallization and device performance. Designed and synthesized two molecules IDCF3 and IDCN, in which isoindigo acts as electron acceptor and benzenyl trifluoride and phenyl cyanide act as electron donor. Two conjugated small molecules with different crystallinity which were tailored be the terminal groups. Organic molecules IDCF3 and IDCN are based on big conjugate surface, strong intermolecular forces is beneficial to molecular self-assembly and form organic crystal. Organic Crystal materials were fabricated into crystal devices and investigated of the performance of device. The result illustrated that the IDCF3 and IDCN based device exhibited WORM memory characteristic.