Memory property of APTMS-mediated Au-SiO2 core-shell nanocrystal memory

Conventional flash memory, utilizing floating gate as charge storage nodes, had met the leakage challenges as the devices tend to be scaling down and have high densities. Nanocrystal (NC) floating gate memory devices, containing nanocrystals as the discrete charge traps, have attracted attention as strong candidates to act as nonvolatile memories devices due to their scalability, electrical isolation and low charge leakage through the tunneling oxide. In this work, an all-solution processed MOS memory structure containing colloidal Au NPs within a sol-gel derived HfO₂ oxide layer was fabricated. We use chemical reduction method to synthesize Au nanoparticles, and use the 3-aminopropyltrimethoxysilane (APTMS) to make the nanoparticles being self-assembled on SiO₂ oxide layer. Finally, it is covered by sol-gel derived Hf0₂ as a control oxide to construct a NC memory structure. To improve the memory device property, we use a simple but effective SAM method to construct an Au-SiO₂ core-shell NC capacitor by means of APTMS as a mediator. The Au-SiO₂ core-shell structure was constructed by a two-run APTMS SAM process which was conducted before and after the SAM of the colloidal Au NPs. The first-run APTMS formed a well-organized monolayer on substrate which was responsible for capturing the high-density of the Au NPs. Next, the second-run APTMS formed an APTMS bilayer around the Au NPs. A following 500 °C-annealing completed the Au-SiO₂ core-shell structure within the HfO₂ layer to form a Si/SiO₂/Au-SiO₂ core-shell/HfO₂ floating structure. The effects of APTMS-mediated SiO₂ shell on the property of memory device were investigated.