A comparison of the chemisorption behaviour of PTCDA on different Ag surfaces

We have studied the adsorption of the molecular semiconductor 3,4,9,10-perylene-tetracarboxylic-acid-dianhydride (PTCDA) on a range of silver substrates, including Ag(1 0 0), Ag(1 1 0), Ag(1 1 1), and Ag(7 7 5). In all of these cases, special attention was placed upon the chemical bonding between the organic molecule and the metal surface, as this is of fundamental importance for the understanding of the organic–inorganic interface. We demonstrate that high resolution electron energy loss spectroscopy (HREELS) in the vibrational energy range is able to provide detailed insight into the intricacies of molecular chemisorption, including electron–vibron coupling effects. Specifically, by analogy with potassium-doped thin films of PTCDA we prove that the Ag(1 1 1) surface imparts metallicity to PTCDA monolayers.