Controllable Fabrication And Charge Storage Properties Investigation Of Monolayer Nanocrystal Granular Films

Nowadays, portable electronic devices have been using more and more widely in people's daily lives. In these devices, Flash Memory plays an important role. The development trend of future Flash Memory can be reduced to larger storage capacity, faster read/write speed, better security for data storage and lower energy consumption during operation. Under this background, a new floating gate structure using discrete nanocrystals to replace continuous polysilicon now attracts great attention. Because nanocrystals floating gate has so many advantages that more and more groups start their research work in this field.The growth of metallic films on oxide films follows Volmer-Weber mechanism. In this work, we developed a simple method to fabricate monolayer nanocrystals granular film by controlling the film's initial deposition thickeness. With this method, we obtained well scattered Ag, Cu, FeNi binary alloy nanocrystals with uniform diameter. Besides, BST nanocrystals with ABO3 structure embedded in silicon dioxide dielectric layer are also fabricated by alternating sputtering.Ag, Cu nanocrystals'average diameter and distributing density were well controlled by adjusting magnetic sputtering conditions during films'deposition. TEM results showed that when the sputtering power during deposition increased, the average diameter of the Ag, Cu nanocrystals increased, but the distributing density decreased. We also found out that the substrate temperature during metallic films deposition had the same effection with annealing. Keeping the substrate at a proper temperature during deposition, the annealing process can be omitted, so the nanocrystal fabrication process will be simplyfized.Untill now, there are not a systemic theory to describe the relationship between the nanocrystals floating gate's micro-structure and its charge storage capabilities. In this article, the relationship between nanocrystals'diameter, distributing density, dielectric layer's permittivity and their charge storage capability will be analyzed. For a single nanocrystal, larger work function, bigger diameter and using dielectric layer with larger permittivity are good for improving its charge storage capability. For nanocrystals floating gate, improving a single nanocrystal's charge storage capability and increasing nanocrystal's distributing density are two ways to improve its charge storage capability.