Chemical bonding and electronic properties of NTCDA/metal interfaces

The electronic structure and chemical bonding at the interface between 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA) film and metal, Au and In were investigated by a photoemission spectroscopy. It was found that the NTCDA film on Au does not react with Au, on the other hand, the diffusion of In atoms into NTCDA film was observed for NTCDA on In, following the reaction with the carboxylic anhydride which is the end groups of NTCDA molecules. This reaction produces in-gap states above the highest occupied molecular orbital of NTCDA. The reactivity between NTCDA and metal seems to strongly depend on the ionization energy of metal atom.