Atomic Force Microscope Current-Imaging Study for Current Density through Nanocrystalline Silicon Dots Embedded in SiO2

Simultaneous surface and current imaging through nanocrystalline silicon (nc-Si) dots embedded in SiO2 was achieved using a contact mode atomic force microscope (AFM) under a tip-to-sample bias voltages of about 5 V. The obtained images were then analyzed using a one-dimensional model of current density, which took account of the spherical shape of the nc-Si dots, the substrate orientation and the sample bias. A comparison between the experimental and theoretical results showed a fair agreement when the current pass through the dot center, although a large difference was found at a higher voltage. In addition, our model predicted tunneling current oscillations due to a change in tip position relative to the dot center.