Investigation of Fabrication Parameters of Poly(N-vinylcarbazole)-Based Non-Volatile Memory Devices

초록

There are many researching fields related to organic electronics such as organic light emission diodes (OLEDs), organic thin film transistors (OTFTs), solar cells, and so on. Recently, the organic memory devices are the interesting subjects including the non-volatile memory (NVM) and the write-once read-many-times (WORM) memory. The organic NVMs possess the reversible bistability between a high conductance (ON state) and a low conductance (OFF state). And the WORM memories have the irreversible properties of ON state after the "writing" process[1-3]. The operations of these devices have been interpreted by the filament (F) model[4], the space charge limited current (SCLC) model[5] and the charge transfer (CT) model[6]. In addition, it has been reported that the memory effect was induced by metallic defects from the vulnerable processes for the fabrication of device[7]. Even though the various models were proposed, it is difficult to clearly classify them because the devices were fabricated by the organic materials with different functional groups and by the dissimilar processes. As depicted in Fig.1, we investigated the major fabrication parameters and the operation properties using the different organic NVMs based on poly(N-vinylcarbazole)(PVK)[8,9]. The organic non-volatile memory devices (NVMs) based on PVK with the different structures and compositions were fabricated and evaluated. The resistance states in the devices were controlled by the external electric field and exhibited the distinct properties; the device with a single PVK layer was a write-once read-many-times memory by the field induced filament as a conduction path and its memory properties depended on the PVK thickness. The PVK/Al/PVK structured device was operated by a space charge limited current model and was sensitive to preparing condition of the internal Al layer. And the device performances with the PVK based charge transfer complex depended on not only the composition of the CT materials but also the surface condition of the bottom electrode.