The structure of copper phthalocyanine and perylene-3,4,9,10-tetracarboxylic dianhydride overlayers on the (111)A surfaces of InAs and InSb

Low energy electron diffraction has been used to investigate the ordered structures formed when copper phthalocyanine (CuPc) and perylene 3,4,9,10-tetracarboxylic dianhydride (PTCDA) are vapour deposited onto the unpassivated, In-terminated InAs(111)A-(2×2) and InSb(111)A-(2×2) reconstructed surfaces. A (12×12)R30° structure is observed on both surfaces after 1–2 monolayers CuPc deposition and a commensurate, diamond-shaped lattice is formed with intermolecular spacing of 1.48 and 1.59 nm on InAs and InSb, respectively. The similarity between the structures, and the unusually large intermolecular spacing, is thought to be related to the presence of exposed second layer group V atoms in the (2×2) reconstruction of the substrate with which the CuPc molecules interact and by which they are pinned. Deposition of PTCDA also leads to the formation of ordered overlayer structures on both surfaces. The diffraction patterns support the presence of six equivalent domains of a rectangular PTCDA lattice that has two molecules per unit cell, the molecular arrangement based on a herringbone structure. The results are consistent with growth occurring with the bulk (102) plane parallel to the substrate surface.