The effect of ultraviolet irradiation treatment on a reduction in contact resistivity at the pentacene/Au interfaces was investigated using current-voltage and X-ray photoelectron spectroscopy in this study. The contact resistivity was drastically decreased from 2.2 x 10(7) to 9.5 x 10(2) Omega cm(2) by the treatment. We suggested that the lower contact resistivity of the pentacene/Au sample with ultraviolet irradiation treatment than the pentacene/Au sample without ultraviolet irradiation treatment may be attributed to the heightened conductivity of pentacene near the pentacene/Au interface resulting from the incorporation of oxygen (from the Au surfaces with ultraviolet irradiation treatment) in pentacene near the interface. (C) 2009 Elsevier B.V. All rights reserved.