Programmable digital memory characteristics of nanoscale thin films of a fully conjugated polymer

This paper reports for the first time the programmable digital memory characteristics of the nanoscale thin films of a fully π-conjugated polymer, poly(diethyl dipropargylmalonate) (pDEDPM) in the absence of doping. This π-conjugated polymer was found to exhibit good solubility in organic solvents and to be easily processed to form nanoscale thin films through the use of conventional solution spin-, roll-, or dip-coating and subsequent drying. Films of the π-conjugated polymer with top and bottom metal electrodes exhibit excellent dynamic random access memory (DRAM) characteristics or write-once-read-many-times (WORM) memory behavior without polarity, depending on the film thickness. All the PI films are initially present in the OFF-state. Films with a thickness of 30 nm were found to exhibit very stable WORM memory characteristics without polarity and an ON/OFF current ratio of 106, whereas films with a thickness of 62-120 nm were found to exhibit excellent DRAM characteristics without polarity and an ON/OFF current ratio as high as 10 ⁸. These memory characteristics are governed by trap-limited space-charge limited conduction and heterogeneously local filament formation. In these polymer films, both the ester units and the conjugated double bonds of the polymer backbone can act as charge trapping sites. The excellent bistable switching properties and processibility of this π-conjugated polymer mean that it is a promising material for the low-cost mass production of high density and very stable digital nonvolatile WORM memory and volatile DRAM devices.