Observation of Oriented Organic Semiconductor using Photo-Electron Emission Microscope (PEEM) with Polarized Synchrotron

Abstract

We have developed photoelectron emission microscope (PEEM) system with excitation of linearly polarized synchrotron X-rays at 30° incidence angle arrangement. The morphology, electronic structure, orientation for P3HT:PCBM hybrid films have been investigated using the PEEM instrument. The sulphur 1s near-edge X-ray-absorption fine structure (NEXAFS) spectra at micro-domains were obtained, where sulphur atoms of thiophene ring were detected. The nature and symmetry in the S 1s excitations of P3HT model cluster were elucidated by DFT calculations that we performed to assign resonant peaks in absorption spectra. We demonstrate that the orientation at micro-domains can be deduced from photon-energy dependencies of PEEM images.

Keywords:

• photo-electron emission microscope (PEEM)
• near-edge x-ray absorption fine structure (NEXAFS)
• orientation
• organic semiconductor
• poly(3-hexylthiophene) (P3HT)
• [6
• 6]-phenyl-C61-butyric acid methyl ester (PCBM)

Acknowledgments

The authors express their gratitude to the staff of the Photon Factory and Iwao Shimoyama of JAEA for their support. This work was undertaken with the approval of the Photon Factory Program Advisory Committee.