Anisotropic ordered Planar Growth of alpha- Sexithienyl Thin Films

We show how the anisotropy of the (1 × 2) reconstructed Au(110) surface can be effectively used to achieve spontaneous ordered planar growth of rodlike conjugated oligomers uniaxially oriented on the substrate. The growth of the first few monolayers of α-sexithienyl (T6) films on the (1 × 2) reconstructed Au(110) surface in ultrahigh vacuum has been investigated by He atom scattering (HAS), scanning tunneling microscopy (STM), and low-energy electron diffraction (LEED). T6 molecules lie flat on the substrate forming long chains along the [110] direction of the Au rows. The interchain spacing is coverage dependent and uniaxially commensurate with the substrate along [001]. Three ordered structures with 12, 16, and 20 A periods are formed during the deposition of the first two T6 monolayers. This T6 overlayer acts as a template for the growth of at least five monolayers which are still planar and orientationally ordered.