Silicon nanograins with aluminum contacts studied by the Density Functional method

The purpose of this study is the evaluation of the effects of metallic contacts on nanocrystalline silicon grains and is based on the use of the Density Functional theory. The structures considered are plated crystalline grains and the contacts are constructed by depositing an aluminum layer on the two opposite sides of the nanograin. The calculations indicate that, as for monolayer films deposited on bulk samples, the aluminum coating has a layered structure without clustering and with minimum intermixing with the silicon atoms. The built-in potential across the entire device has a functional dependence on the geometry of the nanograin and of the contacts. Potentially, this property is important for the fabrication of novel Schottky-barrier devices. However the strength of bonding is generally lower in the structures with contacts and this casts doubts on their stability.