Interaction of Na with sexithiophene thin films

The effects of Na on the electronic structure and electrical properties of α-sexithiophene $\left(\alpha 6T\right)$ are investigated with electron spectroscopic methods under UHV conditions. A shift of the valence-band edge away from the Fermi level, and the evolution of states in the gap, can be determined. In a classical band-structure picture this could be explained as an $n$-type doping process. However, all results point at a high localization of the negative charge at the sulfur atom which is reflected in a very low specific conductivity.