Abstract
In this work, our experimental demonstration of the universal energy level alignment rule at oxide/organic semiconductor interfaces is reported. Photoemission spectroscopy is used to show the three different regimes of the energy level alignment: the lowest unoccupied molecular orbital (LUMO) is pinned to the substrate Fermi level at the extreme low end of work functions; the energy offset of the highest occupied molecular orbital (HOMO) follows the Schottky-Mott rule; the HOMO is pinned to the substrate Fermi level at the extreme high end of work functions. To demonstrate this, fullerene C was deposited on eight different types of transition-metal oxides, ZrO, TiO, NiO, CoO, CuO, VO, MoO, and WO, followed by in situ ultraviolet photoemission spectroscopy.
- Received 28 February 2013
- Revised 9 December 2013
DOI:https://doi.org/10.1103/PhysRevB.89.035202
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