Structure of phthalocyanine overlayers on the (1 0 0) surfaces of InSb and InAs

The structure of free-base phthalocyanine (H2Pc) and copper phthalocyanine (CuPc) overlayers deposited on the indium-terminated InSb(1 0 0) and InAs(1 0 0) (4×2)/c(8×2) reconstructed surfaces have been studied by low-energy electron diffraction and van der Waals (vdW) intermolecular interaction energy calculations. The diffraction pattern for H2Pc grown on InSb(1 0 0) is a superposition of a (3×3) and (√10×√10)R±18.4° structure, whilst no ordered structure is formed when H2Pc is grown on InAs(1 0 0). In contrast, CuPc films exhibit a (3×3) structure on InSb(1 0 0) and a (√10×√10)R±18.4° structure on InAs(1 0 0). These differences can be rationalised by the vdW intermolecular interaction energy calculations of the quadratic unit cells of H2Pc and CuPc. The results show that the lattice structure during the initial stages of thin film growth is influenced strongly by the intermolecular interaction energy of their unit cells.