Synthesis Of Benzothiazole-Containing Push-Pull Structural Organic Small Molecules And Study Of Corresponding Memory Performances

With the rapid development of information storage technology, inorganic semiconductor materials have been unable to meet the requirement of information storage. Recently, organic storage materials have attracted increasing interest than inorganic semiconductor materials due to their simple synthesis process, low cost, structure designability. However, the stability of organic memory device performance is vital in the field of microelectronics, which would determine the future development of organic semiconductor materials. Utilizing the structural tailorability of organic semiconductor materials, we tuned molecular structures and investigate the influences of molecular planarity, distance between donor and acceptor in the molecular skeleton as well as the molecular shape of triphenylamine derivatives on the performances of organic memory devices. Our study is performed in the following three aspects:(1) Investigation of influence of molecular planarity on the performances of electrical memory devices:two D-A type conjugated organic molecules (CZ-BT and TPA-BT) containing benzothiazole acceptor and different donors (carbazole and triphenylamine) were synthesized. The effect of molecular terminal donors on corresponding film morphology and on the performance of electrical memory devices was studied. In addition, the influence of aluminum evaporation rate on the memory properties was also investigated. According to the results, the memory devices based on CZ-BT and TPA-BT all exhibited volatile DRAM behavior. When aluminum evaporation rate was increased from 0.5 A/s to 5 A/s, the CZ-BT-based device remains DRAM behavior while TPA-BT-based device exhibited stable non-volatile WORM behavior. The above results were attributed to relatively large roughness of TPA-BT film, which resulted in penetration of aluminum nanoparticles. These results demonstrate that aluminum evaporation rate plays an important role in the performances of memory devices, which offer an important guidance for the design of stable memory device.(2) Investigation of influence of distance between donor and acceptor in the molecular skeleton on the performances of electrical memory devices:two molecules (CZN-Nayd and CZ-Nayd) with carbazole donor, benzothiazole and 1,8-naphthalimide acceptors were synthesized. It is noteworthy that a phenyl group was added between carbazole donor and benzothiazole acceptor in CZN-Nayd skeleton compared with CZ-Nayd. The effect of distance between arbazole donor and benzothiazole acceptor on the performance of memory devices was studied. Because of relatively better planarity, CZN-Nayd molecules stack more orderly in the film than CZ-Nayd, which is informed by the film XRD patterns. In addition, CZN-Nayd-based device exhibited stable ternary storage performance, while binary storage performance was exhibited by CZ-Nayd-based device. To sum up, the performances of memory devices is effected by tuning the distance between donor and acceptor in the molecular skeleton, which provide a new program to optimize the performances of multilevel data storage device.(3) Investigation of influence of molecular shape of triphenylamine derivatives on the performances of electrical memory devices:three organic molecules (TPA-BBT, TPA-2BBT and TPA-3BBT) were synthesized, and the effect of corresponding molecular shape on performances of memory devices was investigated. The results showed that linear TPA-BBT film exhibited poor surface morphology because serious aggregation occurs, resulting in unstable DRAM behavior. However, the memory devices based on TPA-2BBT and TPA-3BBT exhibited stable DRAM storage characteristic. To further investigate the stability of the three compounds-based devices, the organic layer in every device was annealed at 60℃,80℃,100℃ and 120℃ for 10 h respectively. AFM and XRD results indicated the linear TPA-BBT and TPA-2BBT molecules tended to aggregate in the film with the increase of annealing temperature, resulting in unstable storage performance happened for corresponding devices. In contrast, with the increase of annealing temperature, the surface morphology of the star-shaped TPA-3BBT film became smoother and the molecules stacked more orderly, which was beneficial to achieve stable performance for corresponding device. These results provide a new idea to design triphenylamine derivatives and corresponding memory devices which have stable storage performance.