Effect of Au Nanocrystals Embedded in Conductive Polymer on Non-volatile Memory Window
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1071-F05-14
Effect of Au Nanocrystals Embedded in Conductive Polymer on Non-volatile Memory Window Hyun Min Seung, Jong Dae Lee, Byeong-Il Han, Gon-Sub Lee, and Jea-Gun Park Division of nanoscale semiconductor engineering, Hanyang University, Nano SOI process Laboratory, Room #101,HIT, Hanyang University 17 Haedang-dong, Seoungdong-gu, Seoul, 133-791, Korea, Republic of ABSTRACT Nonvolatile memory devices based on the bistability phenomenon have been researched for the next generation of nonvolatile memory, because of their simple structure and easy fabrication process. Bistability was observed in a poly(n-vinylcarbazole) (PVK) layer, that contain many small, discrete Au nanocrystals, and was sandwiched between Al electrodes. The effect of the Au nanocystals embedded in PVK was investigated and shown to induce a different type of bistability from that exhibited by devices with other structures. The results suggest that Au nanocrystals are essential for conductive polymer memory device to have stable nonvolatile memory behavior and window. INTRODUCTION Recently, many researchers have investigated polymer nonvolatile memory devices because of their low-cost, flexible, simple fabrication [1-4]. The memory phenomenon in these devices is based on the electrical bistability of the material, which has two resistance states that can be set to two different voltages [5-11]. The Simmons-Verderber (SV) model has been used to explain this change in conductivity [12]. Filament formation and destruction [13,14] and electroreduction [15-17] have also previously been considered. Nonvolatile memory devices that use discrete nanocrystals as charge storage sites and exhibit bistability have also been reported [10]. We have fabricated polymer memory devices with structures consisting of Al / PVK / Al, Al(with O2 plasma treatment) / PVK / Al, and Al / PVK / Au nanocrystals / PVK / Al. Depending on the structure, these devices exhibit different nonvolatile memory behavior. In this letter, we discuss how the nonvolatile memory behavior with Au nanocrystals embedded in PVK differ from that of structures without nanocrystals. EXPERIMENT We fabricated three devices with different structures between the Al top and bottom electrodes. The devices were fabricated on cleaned SiO2. The top and bottom electrodes were deposited on the substrate by thermal evaporation in a vacuum chamber (pressure ~ 10-6 torr) The first type of device had only a polymer layer between the electrodes. The polymer (PVK) was dissolved with chloroform, spin-coated on the bottom Al electrode, and baked at 120°C for 2 min to evaporate the solvent away. The second type of device was fabricated by the same processes used for the first type, with the addition of O2 plasma oxidation after the Al bottom electrode was deposited. For the third type of device, a 5-nm-thick Au film was deposited on the spin-coated PVK layer after the bottom electrode deposition. Additional PVK was then spincoated on the Au film and baked. Next, the device was cured at 300°C for 2 h in air to produc
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