We demonstrate a simple and an inexpensive approach for the low-temperature fabrication (<200°C) of low-voltage-operated (<20 V), organic, pentacene-based, nonvolatile memory devices with a high- k hafnium dioxide (Hf O2) main dielectric layer and a polymer electret layer. Two kinds of polymer insulators were used as the electret layer, i.e., a poly(vinylalcohol) (PVA) with strong polar groups and an amorphous poly(methyl methacrylate) (PMMA). We studied the memory characteristics of the corresponding devices, including writing and erasing process, long-term retention, and multiple continuous writing/erasing cycles' endurance testing. The memory windows in devices with PVA can be attributed to the dominant short-lifetime shallow traps located at the PVA/pentacene interface and in the pentacene film, whereas those in devices with PMMA are mainly due to the long-lifetime deep traps located in the PMMA layer. The possible sources of shallow-type and deep-type traps in the memory devices were discussed. Accordingly, the devices with the PMMA layer show superior memory characteristics, including a stable memory window of approximately 2.5 V after 20 V 1 s pulse, retaining 80% of memory windows after 103 s and a good endurance properties.
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