Anomalies of Au film formed on the pentacene surface are investigated as a counterpart of pentacene/Au structure. The Au film is found to contain pentacene derivatives originated from the pentacene layers, and it is composed of grains of various sizes formed as the Au thickness increases. The authors suggest that it is this abundance of peculiarities of the Au film that accounts for the attenuated density of states in the valence band. Deformation of Au grains is accompanied by the lift of the pentacene layers, which, in turn, brings about the device failure. (c) 2007 American Institute of Physics.