Level alignment of gap state at organic-metal interface

Electron emission spectra resulting from thermal collision of He*(2(3)S) atoms with 2,9-demethyl-4,7-diphenyl-1,10-phenanthroline (BCP) films deposited on metal substrates were measured to characterize gap states emerged at the organic-metal interface. For BCP on Au, the gap state is originated from weak chemisorption and serves as a mediator of metal wave functions to the first layer. For BCP on K, organic-metal complex is formed by spontaneous diffusion, yielding the gap states delocalized over the film. In the interfacial region, all the gap state reveals an incommensurate shift with the valence band top of the film, indicating the breakdown of the Schottky-Mott model as evaluating the transport characteristics in organic-metal system. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3204663]