High Performance Transparent Transistor Memory Devices Using Nano-Floating Gate of Polymer/ZnO Nanocomposites.

Chien-Chung Shih,Wen-Chang Chen,Yu-Cheng Chiu,Han-Wen Hsu,Wen-Ya Lee,Hsuan-Chun Chang,Cheng-Liang Liu

doi:10.1038/srep20129

Abstract

Nano-floating gate memory devices (NFGM) using metal nanoparticles (NPs) covered with an insulating polymer have been considered as a promising electronic device for the next-generation nonvolatile organic memory applications NPs. However, the transparency of the device with metal NPs is restricted to 60~70% due to the light absorption in the visible region caused by the surface plasmon resonance effects of metal NPs. To address this issue, we demonstrate a novel NFGM using the blends of hole-trapping poly (9-(4-vinylphenyl) carbazole) (PVPK) and electron-trapping ZnO NPs as the charge storage element. The memory devices exhibited a remarkably programmable memory window up to 60 V during the program/erase operations, which was attributed to the trapping/detrapping of charge carriers in ZnO NPs/PVPK composite. Furthermore, the devices showed the long-term retention time (>105 s) and WRER test (>200 cycles), indicating excellent electrical reliability and stability. Additionally, the fabricated transistor memory devices exhibited a relatively high transparency of 90% at the wavelength of 500 nm based on the spray-coated PEDOT:PSS as electrode, suggesting high potential for transparent organic electronic memory devices.

Highlights

Have the advantage of low-cost and large-area fabrication
ZnO NPs have potential as a charge storage layer for memory applications, the charge retention characteristics need to be further improved
In X-ray diffraction pattern (See supporting information Figure S1), the peaks at 2θ = 31.72, 34.36, 36.18,47.44, and 56.5° are corresponding to the lattice planes (100), (002), (101), (102), and (110) of the hexagonal phase of ZnO35, respectively. This diffraction pattern indicates that the prepared ZnO NPs is the wurtzite crystal phase

Summary

Introduction

Have the advantage of low-cost and large-area fabrication. Recently, semiconducting nanoscale materials such conjugated polymer nanoparticles[28] or cobalt ferrite nanoparticles[16] made from solution process have been used as nano-floating gate. The devices performance are comparable to that of Au NPs, which shows the potential of semiconductor as charge trapping sites. Hirschmann et al employed the ZnO NPs modified by ligand as a charge storage layer in OFET memory[31]. ZnO NPs have potential as a charge storage layer for memory applications, the charge retention characteristics need to be further improved. We blend the hole-trapping polymer, poly (9-(4-vinylphenyl) carbazole) (PVPK), with transparent ZnO NPs for the NFGM devices to improve their memory performance. PVPK is highly transparent in visible region and has a rigid carbazole moiety which could play a role of a hole-trapping site. The experimental results suggested that the fabricated memory devices with a relatively high transparency, large memory window, high on/off current ratio,, and reliable long term stability for organic nonvolatile memory device applications

Methods

Results

Conclusion