Different Film Forming Methods Based On Imide Molecules For Electronic Memory Applications

With the continuous progress of society and the rapid development of information technology,people have entered the information age,making them be eager for high-density storage device.The scientists have studied various types of storage materials,and among them organic storage materials have received extensive attention because of their excellent performance.The typical "sandwich structure" memory device has the advantages of low cost,designable and regulation structure,simple and diversified device preparation process,low energy consumption,and so on,making it possible to become an excellent alternative to traditional silicon-based memory materials.With the realization of multi-dimensional storage of organic memorydevice,the research process of high-density,small-size,low-energy storage devices has been greatly accelerated.This article mainly adjusts the different functional groups of the molecule and prepares the organic film with different film-forming methods to optimize the device performance,which can be divided into the following four aspects:(1)Two organic conjugated small molecules PDICN and PDITH were designed and synthesized.Both small molecules have phthalic anhydride(PDI)as the core conjugated backbone,and the solubility of the molecule in organic solvents is increased by the introduction of long alkyl chains on the imide group.The molecular PDITH device shows binary WORM behavior by introducing electron donating thiophene groups on both sides of the central conjugated backbone.Molecular PDICN device shows stable ternary WORM-type storage behavior by introducing benzocyano groups on both sides.The molecular PDICN has a lower turn-on voltage and greater storage density than a memory device made of the molecular PDITH.This proves that modification of the main conjugated group with different groups can not only improve the storage performance of the material,but also achieve higher memory storage.This has provided a good method for people to explore the higher density storage materials.(2)Two organic conjugated small molecules PDIP and PDIS were designed and synthesized,which are borh introduced a hydrophilic group at one end of phthalic anhydride to form an amphiphilic molecular structure.The molecule PDIP employs a polyether chain as a hydrophilic group,and the molecule PDIS employs a p-toluenesulfonic acid pyridinium salt as a hydrophilic group.In order to improve the deposition of molecules on the substrate,we placed the film prepared by spin coating in an aqueous solvent of methanol and saturated vapor of n-hexane as an oil solvent The different solubility induces molecules to undergo new assembly arrangements.We have found that the film treated with methanol vapor have a tighter and more orderly packing,and the film treated with n-hexane vapor tend to align with amorphous molecules.Both of the memory devices fabricated by the two molecules exhibit typical WORM storage behavior,and after the methanol vapor treatment,the device has a better storage performance.Compared to the molecular PDIP,the hydrophilic group of the molecular PDIS has stronger hydrophilicity,resulting better molecular packing and better performance of the storage device.Compared with the traditional heating maturation film,the solvent maturation film has better selectivity,the driving force of the self-assembly arrangement of the inducing molecule is stronger,and the performance of the memory device is greatly optimized.(3)Three organic conjugated small molecules NIBe,NIQu and NIPy were designed and synthesized.The three molecules are D-A conjugated structurewith naphthalene anhydride as the electron-withdrawing group and the polyphenylene as the electron donating group.The conjugated surface of the three molecules gradually increases.We achieved the preparation of three molecular films by dipping.Compared with the common spin coating method,the film prepared by the dipping and pulling method has a more smooth and ordered thin film,which is very favorable for improving the performance of the memory device.The device prepared with molecule NIBe exhibits FLASH storage behavior.The memory device with the molecular NIQu still exhibit FLASH storage behavior,but the proportion of FLASH storage behavior will be greatly reduced.The NIPy-based memory devices fully exhibit non-volatile WORM memory.This is due to the increase of the conjugated degree of the polyphenylene groups with the three molecules,the charge transfer distance from the HOMO level to the LUMO level becomes larger,and the recovery will become more difficult when the device is excited to the ON1 state.It also realizes the transition of the device from FLASH to WORM storage type.The preparation of the novel organic memory device film is advantageous to the diversification and application of device preparation methods.The method of changing the storage behavior by adjusting the size of the conjugate plane also provides a reference for further study of various storage type mechanisms.(4)In this chapter,using Celestite Blue as a storage material,the film was prepared by electrophoretic deposition.The films prepared by electrophoretic deposition showed a fibrous accumulation,and the devices showed a Flash storage type,whereas the films prepared directly by spin coating showed columnar packing,and the devices showed a WORM storage behavior.WORM storage is exhibited because charge trap transport channels perpendicular to the electrodes can be formed when the molecules are cylindrically stacked.But the film with network-like accumulation cannot form a direct channel connecting the two electrodes.When Applying a reverse voltage,the ON state device may shutdown because of the disappearance of the transmission path,exhibiting flash-type storage.By changing the molecular packing with the film deposition method,different storage types were obtained.The molecular film prepared by electrophoretic deposition method was significantly more uniform and orderly.This is because,the deposition is performed by intermolecular force compared to the traditional spin-coating method.The electrophoretic deposition method drives the molecules to align by applying external force,so the accumulation of molecules will be more closely and orderly,and it is easier to explore the way of stacking.