Bis(phthalocyaninato)yttrium grown on Au(111): Electronic structure of a single molecule and the stability of two-dimensional films investigated by scanning tunneling microscopy/spectroscopy at 4.8 K

Abstract

Scanning tunneling microscopy/spectroscopy (STM/STS) at 4.8 K has been used to examine the growth of a double-decker bis(phthalocyaninato)yttrium (YPc2) molecule on a reconstructed Au(111) substrate. Local differential conductance spectra (dI/dV) of a single YPc2 molecule allow the characteristics of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) to be identified. Furthermore, lateral distributions of the local density of states (LDOS) have also been obtained by dI/dV mapping and confirmed by first principles simulations. These electronic feature mappings and theoretical calculations provide a basis for understanding the unique STM morphology of YPc2, which is usually imaged as an eight-lobed structure. In addition, we demonstrate that bias-dependent STM morphologies and simultaneous dI/dV maps can provide a way of understanding the stability of two-dimensional YPc2 films. © 2010 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.