Structures of a 17,19-hexatriacontadiyne and sashlike polydiacetylene monolayer on MoS2(0001) studied by UHVSTM

Abstract

We have observed a 17,19-hexatriacontadiyne (HTDY) monolayer on MoS 2(0001) and sashlike polydiacetylene atomic sash (AS) molecules derived from the monolayer by scanning tunnelling microscopy under ultrahigh vacuum. HTDY molecules adsorbed at 150 K start to move around on the surface above 240 K to form relatively unstable columnar structures. The column is converted into the AS by UV irradiation. In most AS molecules on MoS2(0001), the alkyl chains are in all-trans conformation but their carbon planes are tilted to the polydiacetylene backbone. This conformer, which is one of the most stable structures for an isolated AS molecule, appears on MoS2(0001) because of very weak molecule-substrate interactions. © 2008 IOP Publishing Ltd.