STM studies of PTCDA supramolecular self-assembling on anisotropic surfaces of reconstructed InSb

Self-assembly of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) molecules on a c (8 × 2) reconstructed InSb(0 0 1) surface as well as on an asymmetrical (1 × 3) InSb(0 0 1) is investigated by means of high resolution scanning tunneling microscopy. The formation of well-ordered one-dimensional molecular lines is observed at low coverage on a former face, whereas on the latter molecules are found as isolated entities. At room temperature spontaneous hopping between energetically similar sites is observed within the lines. At a monolayer coverage flat molecular surface is obtained for both reconstructions, on the c (8 × 2) the layer is composed of neighboring one-dimensional lines, on the (1 × 3) molecular structure does not reveal any long range order. Application of the special experimental procedure provides direct comparison of molecule behavior on both reconstructions of the same sample.