Understanding domain symmetry in vanadium oxide phthalocyanine monolayers on Au (111)

Abstract

Understanding the growth of organic semiconductors on solid surfaces is of key importance for the field of organic electronics. Non planar phthalocyanines have shown great promise in organic photovoltaic (OPV) applications, but little of the fundamental surface characterization to understand their structure and properties has been performed. Acquiring a deeper understanding of the molecule/substrate interaction in small molecule systems is a vital step in controlling structure/property relationships. Here we characterize the vanadium oxide phthalocyanine (VOPc)/Au (111) surface using a combination of low energy electron diffraction (LEED) and scanning tunneling microscopy (STM), obtaining complex diffraction patterns which can be understood using two dimensional fast Fourier transform (2D-FFT) analysis of STM images. These measurements reveal coexistence of three symmetrically equivalent in-plane orientations with respect to the substrate, each of which is imaged simultaneously within a single area. Combining scanning probe and diffraction measurements allows symmetrically related domains to be visualized and structurally analyzed, providing fundamental information useful for the structural engineering of non-planar phthalocyanine interfaces.