The Periodicity Effect on the Charge Storage Characteristic of Multistacked nc-Si Floating Gate

Abstract

Nanocrystalline (nc)-Si/SiO2 multistacked floating gate have been prepared by electron beam evaporation of SiO(x) and SiO2 followed by thermal annealing. HRXTEM reveals that the density of multiply stacked nc-Si quantum dots reaches 9.1 x 10(11) cm(-2) with size of 2-3 nm. The periodicity effect of nc-Si/SiO2 multilayers on the charge storage characteristics of nc-Si floating gate is investigated carefully by using capacitance-voltage (C-V) and conductance-voltage (G-V) measurements at room temperature. It is found the charge storage ability enhances obviously with the periodicity of the multiply stacked nc-Si layer increasing from 2 to 9. The up limit of the thickness for multistacked nc-Si/SiO2 layer is less than 100 nm, which is close to the mean free path of electron in multistacked nc-Si. Charge diffusion among the multistacked nc-Si quantum dots is used to explain the charge storage and retention characteristics.