Electrical Memory Characteristics of Nitrogen-Linked Poly(2,7-carbazole)s

We studied the electrical memory characteristics of the following nitrogen-linked poly(2,7-carbazole)s: poly(9-hexadecyl-2,7-carbazole-alt-N,N-(4-hexadecyloxy)aniline), poly(9-hexadecyl-N,N′-diphenylcarbazole-2,7-diamine-alt-1,3-benzene), and poly(9-hexadecyl-N,N′-diphenylcarbazole-2,7-diamine-alt-4,4′-biphenyl). These polymers are amorphous; however, in thin films, they are slightly oriented in the film plane. All polymers in devices with aluminum top and bottom electrodes were found to exhibit similar dynamic random access memory (DRAM) behaviors without polarity. They are operable with a low voltage (less than ±3 V) and a high ON/OFF current ratio (105–109, depending on the polymer) over the thickness range 8–60 nm. The memory behaviors were found to be governed by space-charge limited conduction and local filament formation. These memory characteristics might originate from the electron-donating carbazole and triphenylamino units in the polymer backbones, which act as charge-trapping sites but have weak electric polarization because of the absence of counterparts. Overall, these polymers are suitable active materials for the mass production at low cost of high-performance, programmable volatile memory devices.