【作者】 刘全；

【导师】 路建美；

【作者基本信息】 苏州大学 ， 应用化学， 2016， 博士

【摘要】 随着当今社会经济的快速发展也伴随着信息爆炸式的增长,基于摩尔定律的传统无机硅存储器件最终将接近其理论存储容量极限。因此设计合成具有高信息存储密度的存储材料和半导体器件是替代硅材料的有效方法之一并有着极其重要的意义。基于有机共轭小分子材料的存储器具有成本低,易于分离纯化,易于加工,响应快速,功耗低等诸多优点,被认为是一种具有广泛应用前景的新型存储材料。近年来有机共轭小分子存储材料已取得一些突破,但在如何进一步提高存储器件的读写循环次数,响应速度,器件维持时间,开关比和存储密度等方面还有很多的工作需要完成。因此,设计和制备具有良好存储性能的新型有机小分子存储材料以及研究探索存储机理逐渐成为超高密度信息存储领域的热点课题。基于此,本论文开展了一系列含有偶氮基团的新型共轭有机小分子化合物的设计﹑合成及器件存储性能的研究工作,并得到了如下研究成果:(1)设计三个具有类似电子结构的位置异构体,研究不同异构体分子的堆积排列有序度及其对导电过程的影响,进而表现出不同的存储性能(二进制存储和三进制存储)。推测了造成三进制存储的主要原因。随后通过理论计算和衰减全反射红外(ATR-IR)证明了该假想,为多进制存储的设计及存储机理的研究提供了有益的参考。(2)设计和合成了三个含邻氟偶氮苯骨架(FAZO)的有机小分子。通过在末端引入推电子基团三苯胺(TPA)和拉电子基团萘酰亚胺(NA),分别得到不同极性的小分子FAZO-1,FAZO-2和FAZO-3。系统的研究了三个小分子的光学,电学和器件的电存储性能。发现较小极性FAZO-1和FAZO-2分子的器件均表现出易失性SRAM性能,而极性较大的FAZO-3分子表现出非易失性三位WORM性能。通过更换金电极验证了存储性能,并进一步通过理论计算理论解释了三个小分子的电存储行为。通过分子极性来调控器件存储性能的方法为今后的分子设计和研究提供有益的借鉴。(3)设计合成了含有吡啶基团的偶氮共轭D-A小分子(AZOCP),并通过分子吡啶基团与樟脑磺酸成盐化作用得到化合物(AZOCP-CSA)。研究了成盐化对薄膜形貌及器件的存储性能的影响。发现表现基于AZOCP-CSA的器件表现出更好的存储性能和器件稳定性。结果表明通过成盐化的方法,可有效改善分子的薄膜形貌和提高分子内/间的电荷转移和电荷传输过程,进而提升其存储性能,对未来高性能有机电子器件的设计具有指导意义。(4)通过新颖高效的合成方法得到八氟取代偶氮苯骨架和全新的全氟取代吩嗪衍生物并以这些分子作为共轭骨架引入推电子基团(三苯胺),分别合成了不同取代的含氟偶氮衍生物TM-1与TM-2和含氟吩嗪衍生物TM-3,通过一些列光电测试比较分子的差异。并作为活性层来制备电存储器件,分析对比器件的存储性能的差异,探讨提升存储器件性能的方法。本论文通过不同的方法对偶氮骨架进行修饰,研究了影响存储性能的因素,讨论并提出了提高存储性能的方法。对高密度数据存储领域的未来发展打下了一定基础。更多还原

【Abstract】 Nowadays, the rapid growth of economic development in society, the information explosion with the traditional device based on Moore’s law will have its theoretical storage capacity limit. The design and synthesis of new high density data storage storage material and semiconductor device has an extremely important significance. Based on the memory of the conjugated organic small molecule material has the advantages of low cost, easy to purify, easy processing, quick response, low power consumption advantages, is considered to be a kind of new memory material with wide application prospect. And in recent years conjugated organic small molecule material has made prominent progress, but in how to further improve the response speed and read and write cycles, switch, device maintain time and storage density has a lot of work needs to be done. Therefore, the design and preparation of good storage properties of novel small organic molecules and exploring the mechanism of storage storage materials has become a hot topic in the field of ultra high density data storage. Based on this, this paper carried out the design of a series of novel conjugated azo containing organic small molecular compounds, research synthesis and storage performance of the device, and the following research results were obtained.:(1) Investigation of Regioisomerism Effects on Multilevel States of a High Performance Organic Molecular Memory: In this chapter, we investigated structure-property relationships of a series of positional isomers, with an emphasis on the understanding of intermolecular interactions and their effects on the conduction process. Such positional-isomers have displayed similar intrinsic electronic properties(the same charge traps) but substantially different(binary or ternary) memory behaviours. Corresponding attenuated total reflection infrared(ATR-IR) studies have shed light on the inherent differences of different molecular interactions before and after applied bias. Our mechanistic investigations suggest that the denser π-π stacking is responsible for a distinct induced intermolecular electric field under bias, which plays a pivotal role in “filling” the charge traps in a stepwise fashion to generate three stable conductivity states. These findings provide a keen insight to the multilevel memory behaviours and offer an exciting opportunity for rational design of novel memory devices.(2) Investigation of the Symmetry and Polarity on multilevel device data storage performance: In this chapter, Three O-fluoroazobenzene-based molecules were chosen as memory-active molecules: FAZO-1 with a D--A2--D symmetric structure, FAZO-2 with an A1--A2--A1 symmetric structure, and FAZO-3 with a D--A2--A1 asymmetric structure. Both FAZO-1 and FAZO-2 had a lower molecular polarity, whereas FAZO-3 had a higher polarity. The fabricated indium--tin oxide(ITO)/FAZO-1/Al(Au) and ITO/FAZO-2/Al(Au) memory devices both exhibited volatile static random access memory(SRAM) behavior, whereas the ITO/FAZO-3/Al(Au) device showed nonvolatile ternary write-once-read-many-times(WORM) behavior. It should be noted that the reproducibility of these devices was considerably high, which is significant for practical application in memory devices. In addition, the different memory performances of the three active materials were determined to be attributable to the stability of electric-field-induced charge-transfer complexes. Therefore, the switching memory behavior could be tuned by adjusting the molecular polarity.(3) Investigation of effect of salification on data storage performance: In this chapter, we report the synthesis of a new organic conjugate molecule, 3-(4-((4-(dimethylamino)phenyl)diazenyl)phenyl)-1-(pyridin-4-yl)prop-2-en-1-one(AZOCP), and its camphorsulfonic acid salt(AZOCP-CSA). The photophysical and electrochemical characterization reveals that an enhanced π-π conjugation is formed in the camphorsulfonic acid salt because of the salification effect. The salification reaction also play an important role in the formation of a more ordered stacking nanocrystalline film as evidenced by AFM and XRD analysis, and thus gives rise to an improved transport of charge carriers. The comparison of device performance demonstrates that the device based on the use of the salificated compound has better resistive memory behaviour in terms of ON/OFF ratio, retention time and rewritable cycle. Isothermal I-V correction and theoretic calculation confirm that the resistive performance is a result of an electric-field-induced charge transfer effect and the enhanced device performance of camphorsulfonic acid salt is due to the presence of a strong salification-induced charge transfer effect. Our experimental finding suggests that the simple but effective salification strategy may find widespread use in promoting performance of other organic resistive memory devices by introducing a strong charge transfer effect.(4) Investigation of the phenazine-π-triphenylamine derivatives on memory device performance: The fluorine substituted azobenzene-π-triphenylamine derivatives: TM-1 and TM-2, and fluorine substituted phenazine-π-triphenylamine derivatives TM-3 were synthesized. The photophysical, electrochemical properties and memory behaviors of these donor-π-acceptor molecules were comparatively investigated. This comparative study of tuning the properties of conjugated D-A-D molecules via aromatic acceptor may be an alternative approach for the design and study of future high-performance memory devices based on new materials.In this paper, we study the factors that affect the memory performance by modifying the azobenzene skeleton of different methods, and discuss the method of improving the memory performance. In addition, puts forward the problems that can be further studied in the future and carry on an outlook of the future study in this realm.更多还原