Quantitative Charge Imaging of Silicon Nanocrystals by Atomic Force Microscopy

Quantitative understanding of charging and discharging of Si nanocrystals in SiO2 films on Si substrate is essential to their application in floating gate nonvolatile memory devices. Charge imaging by atomic force microscopy (AFM) or electrostatic force microscopy (EFM) can provide qualitative information on such system, while a further step is needed. We have developed a generalized method of images, which can solve Poisson equation for multiple dielectric layers, to simulate the charge imaging of Si nanocrystals by non-contact mode AFM under different sample geometries. Simulated images can be compared with experimental images thoroughly to estimate the total amount and distributions of trapped charges, which is also useful in the study of time evolution of charges or dissipation problems.