Study On The Electrical Storage Properties Of Triphenylamine-ruthenium Copolymer And Its Composites

With the increasing demand for information storage and the rapid development of emerging semiconductor technology,the resistive random access memory,has gradually replaced the traditional Si-based semiconductor memory into the public field of vision.Organic film resistive random access memory?ReRAM?based on resistive switching?RS?acts as a promising candidate has been extensively investigated and attracted great attention by scientists and up to the present days.Advantages of ReRAM like fast transition time,low manufacturing consumption,long storage time and more portable,make it available to a wider range of organic storage and information technologies.Based on the above,a conjugated alternating copolymer based on fluorene and triphenylamine,namely poly[?9,9-dioctyl?-2,7-fluorene-co-triphenylamine]?PF-TPA?,in which triphenylamine?TPA?as electron donor and hole transporting group was devised and synthesized on the basis of the Suzuki coupling method in this paper.The structure of the copolymer can be verified by Fourier transform infrared?FT-IR?spectroscopy,hydrogen and carbon nuclear magnetic resonance(¹H-NMR,¹³C-NMR).Severalmemory devices of ITO/PF-TPA/Al,ITO/PF-TPA:MWCNTs/Al and ITO/PF-TPA:TiO₂/Al werepreparedusing fluorene-triphenylaminecopolymer?PF-TPA?,PF-TPA:multi-walled carbon nanotubes?MWCNTs?and PF-TPA:titanium dioxide?TiO₂?hybrid composite materials as active layers respectively.Typical composite-based devices with sandwich configuration,indium tin oxide?ITO?/PF-TPA:MWCNTs/Al and ITO/PF-TPA:TiO₂/Al,were demonstrated superior rewritable flash memory property compare to ITO/PF-TPA/Al devices with a greater ON/OFF state current ratio.Among them,the optimal storage characteristics occurs when the doping concentration of MWCNTs was at a certain value?MWCNTs=5.66wt.%?for ITO/PF-TPA:MWCNTs/Al,which leading to the ON/OFF state current ratio added up to 2 orders of magnitude and the switching threshold voltage reduced to-1 V.For ITO/PF-TPA:TiO₂/Al memory devices,when the doping level of TiO₂ was at0.20 wt.%,the ON/OFF current ratio of the ITO/PF-TPA:TiO₂/Al memory device is as high as 1.5×10⁴,and the switching threshold voltage reduced prominently.In addition,the conductance switching mechanism and the stability of devices were also further discussed and texted.The results show that the charge conduction mechanism of all three types of devices conforms to the space charge limiting current mechanism.Especially in ITO/PF-TPA:MWCNTs/Al and ITO/PF-TPA:TiO₂/Al memory devices,the existence of MWCNTs and TiO₂ act as the electron capture center,which enhances the charge injection and capture.Moreover,all three types of devices show good stability and durability,and no obvious current attenuation was found at a certain test time of 3 h and continuous cycle times of 3×10⁴.These memory devices with excellent bistable non-volatile conductance switching behavior will have a potential application value in the future data storage.