Formation and characterization of dielectric monolayer of norbornene on Ge(100) surface

Abstract

In order to understand dielectric properties of polynorbornene layers on semiconductor surfaces, we have investigated the adsorption structures and electronic properties of norbornene monolayer on the Ge(100) surface using scanning tunneling microscopy under ultrahigh vacuum at room temperature. Norbornene is a monomer of polynorbornene which used as low dielectric material. At coverage of ~0.05 ML, most of norbornene molecules adsorb on top of Ge dimer rows (OT configuration). As the coverage increases, the new feature which located in end-bridge between the two neighboring Ge dimers appears (EB configuration). The OT configuration has most stable adsorption energy in DFT calculation. The saturation coverage of norbornene molecules on the Ge(100) surface is found to be about 0.62 ML. The diffusion of norbornene in OT configuration is observed. Single EB configuration converts into the OT configuration. Scanning tunneling spectroscopy measurement reveals that norbornene monolayer on Ge(100) surface is electrically insulating (has wide band gap) compared with the clean Ge(100) surface.