CdTe-CdSe core-shell 나노입자를 포함한 폴리머 층을 사용하여 만들어진 비휘발성 메모리 소자의 전기적 성질에 관한 연구

Abstract

Hybrid nanocomposites consisting of inroganic and organic materials have considerable attention because of their applications in the nonvolatile memory devices due to the excellent advantages of low power consumption, low cost, high density, and high productivity. Among the various kinds of nanocomposites, the core and core-shell structured nanoparticles have become particularly interesting because of their memory performance in the nonvolatile memory devices. However, even though some studies concerning the nonvolatile memory devices fabricated utilizing the core and core-shell nanoparticles, studies on the electrical property variations due to a CdSe shell layer in the nonvolatile memory devices fabricated utilizing core-shell nanoparticles have not been performed yet. This paper presents data for the electrical property variations due to a CdSe shell layer in the nonvolatile memory devices fabricated utilizing CdTe-CdSe core-shell nanoparticles embedded in a polymer, poly(9-vinylcarbazole) (PVK) or poly(methylmethacrylate) (PMMA), layer. The floating gate layers in two devices were formed by using different toluene solutions (3 wt% polymer, 0.5 wt% CdTe-CdSe nanoparticles and 3 wt% polymer, 0.5 wt% CdTe nanoparticles). The solutions consisting of the polymer and the nanoparticles were spin-coated on the p-Si (100) substrates. After the soft-baking to evaporate the solvent, the Al gate was deposited on the polymer layer by using thermal evaporation. The capacitance-voltages (C-V) for Al/CdTe-CdSe nanoparticles embedded in polymer layer/p-Si device and Al/CdTe nanoparticles embedded in polymer layer/p-Si device clearly showed hysteresis behaviors with a positive or negative shift due to the captured electrons or holes, respectively. The flatband voltage shifts in the devices with CdTe-CdSe nanoparticles and CdTe nanoparticles were quite different. The energy band structure of CdTe-CdSe nanoparticles is a type II nanoparticle, where the conduction band of the CdTe core is higher than that of the CdSe shell. While the injected carriers in the devices with CdTe-CdSe nanoparticles embedded in a PVK layer are captured in the thin CdSe shell, the carriers in the device with CdTe-CdSe nanoparticles embedded in a PMMA layer flow through the CdSe shell. The magnitude of the C-V characteristics flatband voltage has quite different behavior. The capacitance-time (C-t) retentions also show different behavior, respectively.