The simulation of single-charging effects in the programming characteristics of nanocrystal memories

We present a Monte Carlo simulation and modelling method for single-electron nanocrystal memories including the nanocrystal inter-dot effect. A nanocrystal memory is modelled as a network of modified single-tunnel junctions for its programme operation and as a network of channel resistances for simulating drain current to extract its threshold voltage. Additionally, in each modelling, capacitive coupling between each geometrical element was determined using a device simulator. The results show that nanocrystal memory parameters are closely related to both static and dynamic programming characteristics, especially in the single-charging property. When the inter-dot spacing is large, a step-like single-charging feature becomes salient, but the threshold voltage shift between each state decreases. In contrast, when the dots are spatially closer, the threshold voltage shift between each state increases, while the step-like shape vanishes and resembles that of conventional flash memories. From the dynamic viewpoint, a closer spacing of dots makes it easier to charge the nanocrystal memory quantum dots more uniformly. The presented method will be helpful for the design of single-electron nanocrystal memories. M This article features online multimedia enhancements (Some figures in this article are in colour only in the electronic version)