The memory effects of the metal nanocrystals were found to be more pronounced than those of the semiconductor nanocrystals. Various metal nanocrystals as charge storage nodes are reviewed. The memory effects have strong relationship with the work function, and the work function can be modulated by changing the metal species. By tunneling dielectrics engineering, the optimum I-GWrite/Erase/I-G Retention ratio can be obtained. (c) 2006 Elsevier Ltd. All rights reserved.