Energy-level alignment at NTCDA/metal and PTCDA/NTCDA interfaces studied by UPS

Energy level alignments for perylenetetracarboxylic dianhydride (PTCDA)/Nap hthalene tetracarboxylic anhydride (NTCDA)/Au and NTCDA/In interfaces have been investigated by ultraviolet photoemission measurements. It was found t hat the energy position of the highest occupied molecular orbital (HOMO) of NTCDA is 1.8 eV below the Fermi level and is 0.3 eV above the HOMO of PTCD A. In the case of the deposition of NTCDA on In, a peak appears near the Fe rmi level. suggesting an in-gap state. The appearance of the in-gap state c an be interpreted as a result of chemical reaction between NTCDA and In. (C ) 2000 Elsevier Science B.V. All rights reserved.