Electronic structure of C ₆₀ on Au studied by using X-ray and uv photoelectron spectroscopy

The electronic structure of C ₆₀ on Au was analyzed by using X-ray and ultraviolet (uv) photoelectron spectroscopy. The energy level alignment was studied by using the onset of the highest occupied molecular orbital level and the shift of the vacuum level of the C ₆₀ layer, which was deposited on a clean Au surface in a stepwise manner. The measured onset of the highest occupied molecular orbital energy level was 1.7 eV from the Fermi level of Au. The vacuum level was shifted 0.54 eV toward higher binding energy with additional C ₆₀ layers, which means an interface dipole exists at the interface between C ₆₀ and Au. The C 1s spectra show that band bending exists at the interface between C ₆₀ and Au. These results indicate that the hole and the electron injection barrier heights are 1.2 eV and 1.4 eV relatively at the interface between C ₆₀ and Au.