Syntheses And Electronic Memory Characteristics Of Small Molecules And Polymers Containing Azo-naphthylamine Moieties

With the rapid development of science and technology, memory devices based onsilicon semiconductor are difficult to fulfill the requirements of high density data storagerequirements for their own physical and economic deficiencies. Therefore, looking for newmaterials to replace the traditional inorganic materials is becoming a hotspot in recentyears. Compared with traditional inorganic silicon materials, organic and polymericmaterials have several significant advantages: low-cost, rich structure flexibility,light-weight and super-high data storage density. In our group, the technique of molecularstructure design is used to regulate the performance of device, realizing a great leap from“binary” to “ternary” which enhanced the storage capacity quite a lot. In this paper, a seriesof small molecules and polymers containing azo-naphthylamine moieties were synthesizedand characterized and used to investigate the effects of molecular structure andintramolecular arrangement for the storage performance of memory device,(1) Functionalized polymers with the side chains including azo groups weresynthesized. This kind of polymers having excellent solubility can be made into films byaccessible spin coating method. In order to maximize the performance of correspondingdevices, we adjusted the length of flexible chain after great deliberation. The devices oftwo polymers, one contains no flexible chain and the other owns a flexible chaincontaining two carbons, can be switched from the low-conductivity state to thehigh-conductivity state at a voltage sweep from0to-3V. The latter polymer can be closedto intermediate conductance states then to OFF state, while the former one can only bepartly closed when a reverse voltage was applied. This ternary Data-Storage is the first tobe reported in the field of polymers. The conduction mechanism can be explained in termsof field-induced conformational ordering of the polymer chains, and the “traps” of Azo thatretarded the mobility of the charge carriers, both of which could be elucidatedunambiguously from UV-vis absorption spectra and X-ray diffraction patterns.(2) Small Molecules with different film-forming properties and electron traps were synthesized and characterized in the meantime. An electrical memory device with theindium-tin oxide (ITO)/Small-Molecule/Al sandwich structure was fabricated and itselectrical performance was investigated. WORM storage devices with different thresholdvoltages were obtained, some of which present “ternary” property. The relationshipbetween turn-on voltage and the energy barrier between active materials and electrodeswas revealed by the cyclic voltammetry measurement. The molecular film-formingproperties and electron traps are responsible for device performances collectively, whichcould be elucidated unambiguously from UV-vis absorption spectra and X-ray diffractionpatterns.