Designed Workfunction Engineering of Double-Stacked Metal Nanocrystals for Nonvolatile Memory Application

A double-stacked nanocrystal (DSNC) flash memory is presented for improvement of both program/erase (P/E) speed and data retention time. Four combinations of nickel (Ni) and gold (Au) (Ni/Ni, Au/Au, Ni/Au, and Au/Ni) are used as charge storage DSNC materials and are compared from the perspective of memory performance. Through experimental results for P/E efficiency and retention time, the optimized energy band lineup for faster P/E and longer charge retention is presented. A combination of a deep potential well at the top and a shallow potential well at the bottom exhibits optimized performance in P/E, and this combination also shows the longest data retention characteristics.