Ordering of copper phthalocyanine films on functionalized Si(111)

Abstract

The adsorption and growth of copper phthalocyanine (CuPc) has been studied on passivated Si(111) surfaces. As passivating agents, Ga, Bi, and Ag were used, leading to a 3×3-R30∘ reconstruction of the surface in each case. X-ray photoemission spectra indicate a non-dissociative adsorption. The structure and morphology have been investigated with low-energy electron diffraction and scanning tunneling microscopy. For Ga-terminated substrates, ordered domains are observed with random azimuthal orientation. Upon further deposition, three-dimensional islands are found. In case of Bi-terminated Si(111), a rather smooth morphology with high structural disorder evolves, which is attributed to an inefficient surface diffusion. The CuPc films with best structural order, with a nearly square unit mesh, and with smooth morphology are achieved on Ag-terminated Si(111). The differences in structural and morphological evolution of the CuPc films for Ga, Bi, and Ag surface passivation are discussed in terms of interfacial interaction and occupied versus unoccupied local density of states.