MOLECULAR-ORIENTATION IN VACUUM-DEPOSITED POLY(THIOPHENE) FILM STUDIED BY 2ND-HARMONIC GENERATION

The molecular orientation of the vacuum-deposited polythiophene (PT) film has been studied by second-harmonic generation (SHG). The polythiophene main chain is preferably oriented to be perpendicular to the substrate normal. The chain tilt angle from the surface normal decreased with increasing substrate temperature during the vacuum deposition. These results are consistent with the reported electron diffraction results. It has been considered that the SHG originates from the modification of the electronic states of PT due to the interaction between PT and the glass substrate.