Si nanocrystal based memories: Effect of the nanocrystal density

Si nanocrystals designed for memory applications were prepared in a layered arrangement by using a $SiOx∕SiO2$ multilayer structure with a variation of the stoichiometry parameter $x$ from 0.9 to 1.63. The stoichiometry of the $SiOx$ layers is controlled by adjusting the oxygen pressure during the growth which influences the resulting area density of the Si nanocrystals after high temperature annealing from around $(2.8–0.93)×1012∕cm2$⁠. The tuning of the Si nanocrystal area density in the layers is demonstrated by transmission electron microscopy as well as by comparison of capacitance-voltage and photoluminescence measurements. The influence of the nanocrystal density on the charge behavior is demonstrated and discussed. Our method realizes a simple way to control the area density by maintaining equally sized nanocrystals, that gives unique possibilities to study the influence of the nanocrystal density on the electrical properties.