Dependence of the Field and Charge Distribution at a Semicon/Polyethylene Interface on the Press-Molding Process Derived from Kelvin Probe Force Microscopy

Knowledge about the electronic properties of interfaces between different materials is fundamental for understanding charge transfer. This is particularly relevant in High Voltage Direct Current (HVDC) polyethylene (PE) insulated power cables with semicon (SC) electrodes. We investigate the PE-SC contact interface of lab made SC/PE/SC slices using Peak Force - Quantitative Nano Mechanics (PF-QNM) and Kelvin Probe Force Microscopy (KPFM) techniques. Field and charge distributions are derived at nanoscale and compared for different PE cover-layer materials (PolyEthylene Terephthalate (PET) or Aluminum (AI)) used during the molding process. Whatever the process, negative or positive charge clouds spread over 2-3 μm in PE. The maximum charge density is strongly influenced by the cover-layer material, in correlation with the diffusion of oxidized groups from PET, in spite of a smoother roughness when compared to Al. We also report on results where a small voltage was applied to the structure.