The assembly of molecular building blocks on crystalline surfaces into ordered nano-architectures is more and more an established approach towards the creation of novel materials with outstanding properties. The surface science methodology allows to investigate the morphology of novel molecular structures in the monolayer or sub-monolayer regime (e.g. self-assembled long range ordered 2D networks), and their electronic properties (e.g. density of states, charge transfer, HOMO-LUMO coupling). Eventually it may lead to a clear understanding of the molecule–to–substrate adsorption geometry together with the interaction between the first layer and the hosting surface. The use of techniques such as Scanning Tunneling Microscopy (STM), Low Energy Electron Diffraction (LEED) and Angle Resolved Photoemission Spectroscopy (ARPES) allows to enlighten on most of the unknown of those systems sorting out their electronic structure and the geometric arrangement. Nanosized polycyclic aromatic hydrocarbons (PAHs) are a class of compounds with exceptional electronic, self-assembling and synthetic properties.[1-3]
We show a few examples of PAHs adsorbed on the atomically flat Cu(111) surface. In our case studies we demonstrate that molecular derived electronic states can be disclosed with the ARPES based momentum mapping methodology  as long as the compounds, from which these states originate, can be assembled in long range ordered 2D networks on a well defined substrate, as it is revealed by STM and LEED.
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