A systematic spectroscopic study of the FePc–Si interfaces

A systematic spectroscopic study on the interfaces between the organic molecular semiconductor and the (1 1 0) phase of the doped polysilicon has been carried out using valence and core-level photoemission spectroscopy. All photoemission spectra (UPS/XPS) exhibited shifts in the positions of the peaks following the deposition of the organic films. A set of clearly resolved valence band features is found associated to the dispersion of the molecular orbitals. The nonexistence of Fermi edge in the FePc films is thought to account for its semiconducting nature. The thickness dependent change in the work function of the substrate is noticed and a minute amount of charge transfer is found. The asymmetric C1s peak is resolved into three components, reflecting photoemission from multiple sites within the organic molecule. A larger shift in the benzene carbon (Cb) as compared to the pyrrole carbon (Cp) peak suggests that more charge transfers from the former carbon to the substrate. The observed negative sign of the sizable interface dipole potential indicates that the guest molecule and the hosting substrate have donor and acceptor character, respectively. Furthermore, the dipole width, i.e. d=1.35 Å, is determined on the basis of the measured quantities and basic physics.

► PES spectra exhibited shifts in the organic features following the deposition of the organic films.
► A thickness dependent change in the work function of the substrate is noticed.
► The nonexistence of Fermi edge in the FePc films is thought to account for its semiconducting nature.
► It is found that greater charge transfers from Cb as compared to the Cp carbon to the substrate.
► The eD value suggests that FePc and Si (1 1 0) have donor and acceptor character, respectively.