Molecular structure and carrier distributions at semiconductor/dielectric interfaces in organic field-effect transistors studied with sum frequency generation microscopy

Infrared-visible sum frequency generation (SFG) microscopy was applied to the observation of semiconductor/dielectric interfaces in organic field-effect transistors fabricated with pentacene films and polyvinyl phenol dielectric layers. SFG intensity at the interface was greatly increased by carrier injection. The large enhancement in SFG intensity enables us to observe clearly the vibrational spectra of molecules and the spatial distributions of charge density at the interface.