Diffusion of Li in the silicon oxide films and evaluation of Li-induced surface potential

The lithium doped and non-doped SiO2 films were prepared by dip-coating method. Lithium atoms diffuse very fast in silicon oxide film and silicon substrate. As grown silicon nitride film prepared by plasma-enhanced chemical vapor deposition (PECVD) is insufficient as barrier layer for lithium diffusion. Lithium atoms can keep in the silicon oxide film by using the silicon nitride films densified by high temperature heat treatment. Surface potential of the insulating films involved alkaline metal atoms can be measured by Kelvin probe force microscope (KFM). Although the data have considerable scatterings, the surface potential of the lithium doped films was showed to be relatively positive. It is also found that the hydrogen atoms incorporated in the silicon nitride films used as diffusion barrier layer have a large influence on the surface potential. The possibility of KFM is confirmed for estimation of the surface potential of the insulating films with charged atoms.