Sexithiophene ultrathin films on passivated Si(0 0 1) surfaces: Growth and electronic structure

• Core levels of α-6T thin films were investigate by high-resolution photoelectron spectroscopy.
• The origin of the in-plane orientation is partly ascribed to the interaction with the Si–OH species.
• The origin of the in-plane orientation is partly ascribed to the geometrical effect.
• The origin of the molecular orientation/packing structure was examined.

We investigated the electronic states of αα-sexithiophene (αα-6T) on three passivated Si(0 0 1) surfaces, oxidized Si(0 0 1), water-adsorbed Si(0 0 1), and ethylene-adsorbed Si(0 0 1), by means of high-resolution photoelectron spectroscopy using synchrotron radiation. The main purpose of the present study was to identify the origin of the marked difference in molecular orientation on these substrates. We found that the interaction of αα-6T molecules with Si–OH species should be the dominant reason for the in-plane orientation. On the other hand, the predominance of the in-plane orientation on ethylene-adsorbed Si(0 0 1) could not be simply explained by the chemical interaction but was ascribed to the geometrical effect of the surface corrugation. We investigated changes in the core levels upon αα-6T deposition on passivated Si(0 0 1) surfaces and interpreted the results based on the charge transfer scheme.

Figure optionsDownload as PowerPoint slide