Growth mode and molecular orientation of phthalocyanine molecules on metal single crystal substrates: A NEXAFS and XPS study

We report on near-edge X-ray absorption and X-ray photoemission experiments for the large π-conjugated organic molecule metal-free phthalocyanine (H2Pc) on two different single crystal surfaces. Results from H2Pc deposited on Ag(1 1 1) at 300 K show a clear linear dichroism indicating that the film grows as islands with the molecules lying essentially flat. On a Ni3Al(1 1 1) and a cooled Ag(1 1 1) substrate, however, the molecules form a homogeneous film and have an average tilt angle of 45-60°. The different film structure is the result of a different molecule-substrate interaction.