基于苯并噻二唑的共轭高分子材料的合成及其阻变存储性能

Synthesis and Resistive Switching Performance of Benzothiazole-Based D-A Type Conjugated Polymer

设计合成了一种新的基于苯并噻二唑的电子给体(D)-电子受体(A)型高分子阻变存储材料聚{[4,4′-(2,7-二苯基-9H-芴-9,9-二基)双(N,N-二苯基氨)]-alt-[4,7-双(4-正十二烷基-5-乙烯基噻吩-2-基)-苯并[c][1,2,5]噻二唑]}(PFVT)。以PFVT为活性材料制备的Al/PFVT/ITO(ITO:氧化铟锡)器件在室温下展现了非易失性阻变存储(RRAM)性能。器件经过50次开启、关闭循环操作,获得的平均开启和关闭电压分别为(-0.54±0.01) V和(2.42±0.05) V,电流开/关比为1.50×103。在循环操作期间的编程电压变化小于2.1%,器件展现出优良的可靠性。经200℃退火处理后,薄膜材料的结晶性增加,器件的平均开启和关闭电压减小,分别为(-0.49±0.01) V和(2.27±0.02) V。器件存储机制归属于电场诱导的分子内电荷转移。利用空间电荷限制电流模型和欧姆电流模型可以分别完美拟合OFF态和ON态电流。为了比较,用苯环替代高分子结构中的9,9-二(4-二苯胺基苯基)-芴单元,合成了聚{4-(4-十二烷基-5-(4-甲基苯乙烯基)噻吩-2-基)-7-(4-十二烷基-5-(丙烯-1-基)噻吩-2-基)苯并[c][1,2,5]噻二唑}(PPVT),该材料展现出类似的阻变存储性能。与PFVT相比,PPVT的开启电压明显变大,而电流开/关比则小了一个数量级,用苯环取代大体积芴单元后材料的热稳定性急剧下降,带隙增大。

A novel benzothiadiazole-based donor-acceptor type polymer,resistive random access memory(RRAM) material,poly{[4,4'-(2,7-diphenyl-9H-fluorene-9,9-diyl)bis(N,N-diphenylaniline)]-alt-[4,7-bis(4-dodecyl-5-vinylthiophen-2-yl)benzo[c][1,2,5] thiadiazole]}(PFVT) was synthesized.By using PFVT as the active layer,the as-fabricated electronic device with a configuration of Al/PFVT/ITO(ITO:indium tin oxides) exhibites a nonvolatile RRAM performance.During 50consecutive cycle-to-cycle measurements,the observed average switch-on voltage,switch-off voltage and ON/OFF current ratio are(-0.54 ± 0.01) V,(2.42 ± 0.05) V,and 1.5×103,respectively.The cycle-to-cycle variation for the programming voltage is less than 2.1%,suggesting excellent reliability.After thermal annealing at 200 ℃,the switch-on and switch-off voltages decrease to(-0.49±0.01) V and(2.27±0.02) V,respectively,due to the enhanced material crystallinity.The switching mechanism can be assigned to the intramolecular charge-transfer occurred in the materials system.The ON and OFF-state currents can be fitted by the Ohmic current model and space-charge-limited current model,respectively.The switchon voltage is highly associated with the bandgap of the materials.For comparison purpose,4,4′-(2,7-diphenyl-9H-fluorene-9,9-diyl)bis(N,N-diphenylaniline) was replaced with phenyl group to synthesize poly[4-(4-dodecyl-5-((E)-4-methylstyryl)thiophen-2-yl)-7-(4-dodecyl-5-((E)-prop-1-en-1-yl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole](PPVT).In contrast to PFVT,PPVT also shows the similar RRAM performance,with a bigger switch-on voltage and a smaller ON/OFF current ratio.Replacement of bulky fluorene unit with phenyl unit leads to a sharp decrease in the thermal stability of the material and an increase in the bandgap.