Experimental estimation of the electric dipole moment and polarizability of titanyl phthalocyanine using ultraviolet photoelectron spectroscopy

Changes in the work function (WF) and binding energy of the highest occupied molecular orbital (HOMO) level in a titanyl phthalocyanine-(OTiPc) graphite system were studied as a function of OTiPc coverage by ultraviolet photoelectron spectroscopy. We observed that the WF increases with the coverage of the oriented OTiPc until the formation of the monolayer, while the energy position of the HOMO level stays almost unchanged with respect to the Fermi level. By analyzing the observed coverage dependence of the WF using the Topping model, we estimated the electric dipole moment and polarizability of OTiPc in a monolayer.