Dependency of Nonvolatile Memory Behavior on Curing Temperature for Au Nanocrystals Embedded in PVK
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0965-S09-14
Dependency of Nonvolatile Memory Behavior on Curing Temperature for Au Nanocrystals Embedded in PVK Byeong-il Han1, Chang-Kyu Lee1, Jong-Sung Kwon1, In-Chul Na1, Jea-gun Park1, and YoungMin Kim2 1 Electrical & Computer Engineering, Hanyang University, #101 HIT, Hanyang University, Haengdang-dong, Seongdong-gu, Seoul, 133-791, Korea, Republic of 2 Electron Microscopy Team, Korea Basic Science Institute, 52 Eoeun-dong, Yusung-gu, Daajeon, 305-333, Korea, Republic of
ABSTRACT The bistability of Au nano-crystals embedded in poly(N-vinylcarbazole) (PVK) was observed. The dependency of the resulting nonvolatile memory behavior on the curing temperature for the Au nano-crystals was investigated. For devices fabricated with different curing temperatures, the current-voltage characteristics were measured, and the formation of the Au nano-crystals was investigated by high-resolution cross-sectional transmission electron microscopy (TEM). The nonvolatile memory behavior requires suitable formation of the Au nano-crystals, which depends on the curing temperature. INTRODUCTION Recently, many researchers have investigated organic nonvolatile memory devices because of their low-cost, flexible and 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 at two different voltages [5-11]. The Simmons-Verderber (SV) model has been used to explain such a change in conductivity [12]. Filament formation and destruction [13,14] and electro-reduction [15-17] have also previously been considered. Nonvolatile memory devices that use discrete nano-crystals as charge storage sites and exhibit bistability have also been reported [10]. To optimize the performance of this type of memory device, we have fabricated an organic device, with a structure consisting of Al/PVK/Au nano-crystals/PVK/Al, that exhibits bistability. In this letter, we discuss the effect of the Au nano-crystals on the creation of bistability.
EXPERIMENT The device in this study was fabricated on cleaned SiO2. First, the Al for the bottom electrode was deposited on the substrate by thermal evaporation in a vacuum chamber (pressure ~10−6 torr). The PVK was dissolved with chloroform, spin-coated on the Al electrode, and baked at 120°C for 2 min to evaporate the solvent away. Subsequently, a 5-nm-thick Au film was deposited on the PVK. Additional PVK was then spin-coated on the Au film and baked. Next,
the device was cured at 300℃ for 2 h in air to produce the Au nano-crystals. Finally, the Al for the top electrode was deposited on the cured device. Figure 1 shows a cross section of the device structure and the chemical structure of PVK. In addition, the dependency of the bistability on the curing temperature was investigated by electrical measurement with an Agilent 4270B and by high-resolution cross-sectional transmission electron microscopy (TEM). Al PVK PVK
Al SiO2
Si
Figure 1. Device structure of Al/PVK/Au nano-crystals/PVK/Al and the chemical st
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