Molecular strings at surfaces: 'forced assembly' of bithiophene on a sulphur p(4x1)Ni(110) surface

The assembly of organic molecules into an ordered array of rows by chemical patterning of a metal single crystal substrate surface is reported. The p(4 x 1)S reconstruction of the Ni(110) surface provides a suitable template for the formation of 1D bithiophene strings due to the well separated Ni rows left exposed to provide adsorption sites on a surface, which is otherwise passivated by sulphur. Physical vapour deposition of the bithiophene was performed under ultrahigh vacuum conditions and the nature of the molecular films was assessed by a variety of surface science techniques including LEED, HR-XPS, ARUPS and HREELS. It is shown that, while on the clean Ni a strong a bonding does not allow molecular ordering, on the S-modified surface bonding is through the molecular S and the reduction of the molecule-substrate interaction allows self-assembly. A well ordered molecular monolayer consisting of strings of bithiophene in a syn conformation results. (C) 1998 Elsevier Science S.A. All rights reserved.