Abstract
Polar organic molecules, chloroaluminum phthalocyanine (ClAlPc), adsorbed on the Ag(111) thin film and Ag(111) crystal were investigated using angle-resolved photoelectron spectroscopy (ARPES). The absorption configurations, Cl-up and Cl-down, were controlled by adjusting the deposition rate of ClAlPc; slow deposition can leads to the Cl-down configuration on the both substrates of Ag(111) single bulk crystal and thin films, and post annealing about 60˚C for 30 minutes flips Cl-down to Cl-up configuration. We studied irradiation-exposure effects on both configurations. We found that some of Cl-down ClAlPc were tilted or flipped to Cl-up configuration after irradiation exposure. And for Cl-up ClAlPc, higher irradiation flux is needed to change adsorption configurations by breaking Al-Cl bond of ClAlPc. Moreover, we made an interesting discovery that the adsorption stability of Cl-down configuration is a lot higher on the Ag(111) thin film than the Ag(111) bulk crystal; correspondingly, the energy positions of molecular energy states (MES) as well as the work function change shift to higher values. This indicates more charge transfer from Ag atoms to ClAlPc for the former. This is ascribed to the large strain effect on Ag thin films from the underlying Ge(111) substrate which has 28% lattice mismatch with Ag(111); the size of hollow sites between Ag atoms is thus likely enlarged, facilitating the stable anchoring of Cl atom of ClAlPc in Cl-down configuration