Low-temperature formed quaternary NiZrSiGe nanocrystal memory

This study investigated the formation of quaternary NiZrSiGe nanocrystal (NC) flash memory by using the sol-gel spin-coating method. A solution of nickel dichloride, zirconium tetrachloride, silicon tetrachloride, and germanium tetrachloride was used as a precursor to form the sol-gel thin film. Unlike the NiZrSi control sample that exhibited a continuous and smooth film after anneal, the NiZrSiGe transformed into NCs after undergoing thermal annealing in an O₂ ambient. Based on TEM analysis, the size of the nanocrystals was 2-4 nm. Compare to the NiZrSi control sample, the NiZrSiGe memory exhibits improved electrical performance in memory windows, program/erase speed, and device reliability. The memory window of the quaternary NiZrSiGe nanocrystal memory was approximately 3.84 V. The retention characteristics of the memory can be up to 10⁶ s at room temperature measurement with an approximately 8% charge loss, or an approximately 10% charge loss at 85°C measurement. The V_t shift of the program and erase states after 10⁴ cycles was approximately 1 V. These results show that quaternary NiZrSiGe nanocrystal devices exhibit excellent memory performance.