Charge storage characteristics of Ni nanocrystals formed by synchronous crystallization

Abstract

The rapid thermal annealing (RTA) nano-crystallization method is widely used in the metal nanocrystal fabrication process. However, the high temperature (usually 600–900 °C) in the RTA process will worsen the performance and reliability of devices. A novel method has been proposed to grow metal nanocrystal by synchronous in situ nano-crystallization of metal thin film (SINC), which is able to resolve the problems mentioned above. Compared with Ni nanocrystals (NCs) formed by RTA, Ni NCs prepared by SINC can obtain more energy to crystallize, and its crystallization temperature is greatly reduced. A large memory window (2.78 V) was observed for Ni NCs deposited by SINC at 300 °C. However, the largest window is only 1.26 V for Ni NCs formed by RTA at 600 °C. A large change (from 0.20 to 4.59 V) of the memory window was observed while the operation voltage increased from 0 to ±10 V, which is due to an occurrence of strong carrier trapping in Ni NCs. Flat-band voltage shift rapidly increases to its saturation value, which indicates that electron/hole trapping in Ni NCs mainly occurs at the initial stage of the program/erase process. A theoretical model was proposed to characterize the charging and discharging processes.