The molecular orientation and electronic structure of 3,4,9,10-perylene tetracarboxylic dianhydride grown on Au(111)

The interface electronic structure, molecular orientation and surface morphology of the organic semiconductor 3,4,9, 10-perylene tetracarboxylic dianhydride (PTCDA) grown on Au (111) surface have been studied by means of X-ray photoelectron spectroscopy (XPS), synchrotron radiation ultraviolet photoelectron spectroscopy (SRUPS), near edge X-ray absorption fine structure spectroscopy (NEXAFS) and atomic force microscopy (AFM). It can be seen from the SRUPS results that the Shockley-type Au (111) surface state near the Fermi level extinguishes immediately after sub-monolayer of PTCDA is deposited onto the Au surface without the emergence of interface hybrid state. This indicates that a charge transfer process takes place at the interface between PTCDA molecule and Au(111), but does not lead to strong chemical reaction. Angle dependent NEXAFS and SRUPS show that the PTCDA overlayers are ordered and the molecules lie flatly on the Au(111) surface. According to the AFM images and the evolution of Au 4f(7/2) and C 1s integral intensities with increasing film thickness, the typical Stranski- Krastanov growth mode is proposed for PTCDA deposition on Au(111) surface, that is, layer by layer growth followed by island growth mode. The Dewetting transition occurs between the 2D and 3D growth modes.