This Letter, reports the hole-injection characteristics of an ultra-thin, transparent gold electrode derivatized with a thiolate polar monolayer into the amorphous molecular semiconductor, N,N'-bis(3-methylphenyl)-NNdiphenyl-1,1'biphenyl- 4,4'-diamine (TPD). Thermionic emission with image force lowering gives an excellent description of the injection mechanism over a large range of temperatures and electric field strengths, yielding a zero field Schottky barrier height of similar to 0.4 eV. This study demonstrates that derivatizing the surface of this novel gold electrode with a 4-nitrophenylthiolate monomolecular layer is an effective means of circumventing the abrupt negative vacuum level shift, which forms when TPD is thermally deposited onto gold electrodes. (c) 2006 Elsevier B.V. All rights reserved.