Band alignment on a nanoscopically patterned inorganic-organic interface

The band alignment of organic semiconductors on a nanoscopically patterned surface is investigated for submonolayer coverages to thin molecular films of bithiophene, using ultraviolet photoelectron spectroscopy and work function measurements. The Cu (110)-(2x1)O stripe phase, used as a substrate, consists of alternating stripes of clean and oxygen passivated copper, with a respective stripe diameter of three to four times the molecular length. For the first molecular layer, a superposition of bithiophene spectra, offset from each other by 1 eV, reflecting the interface dipole differences on Cu (110) and Cu (110)-p(2x1)O, was found. However, after completion of the second layer, the observed band alignment between the substrate and the overlayer is determined by the average interface potential and the underlying substrate pattern is obscured. (C) 2003 American Institute of Physics.