Photoemission study of oxygen and Au modification of doped copper phthalocyanine

The modifications of the electronic structure of heavily Cs-doped copper phthalocyanine (CuPc) by oxygen exposure and by Au deposition have been investigated with ultraviolet and x-ray photoemission spectroscopy. To a certain degree, both oxygen and Au act like p-type dopants and compensate the n-doping effects by Cs in CuPc, including the energy level shift and the gap state. However, the compensation to the electronic structure is incomplete, and it is found that the effect of 1 ML of Au deposition is about equivalent to 300 L (1 L=10(-6) torr s) of oxygen exposure. The quenching of the Cs-induced gap state is observed to depend exponentially on the Au deposition. The core level behavior provides additional information on the charge redistribution in the CuPc molecule. (C) 2007 American Institute of Physics.