FIG. 1. He I UP-spectra. The center graph shows the
complete spectra as measured. The bottom spectrum
corresponds to the pristine, in-vacuum cleaved, HOPG
surface. The subsequent spectra were measured after
each of the P3HT deposition steps. On the right, the
valence bands/HOMO spectral region is shown with removed
background. On the left, the secondary edge feature
is shown normalized allowing better comparison.
The insert shows the evaluation of the HOMO cutoff of
the 3.15 ml deposition step for the determination of ionization
energy and orbital alignment at the HOPG
interface.