Molecular-scale investigation of C60/p-sexiphenyl organic heterojunction interface.

In situ low-temperature scanning tunneling microscopy (LT-STM) and ultraviolet photoelectron spectroscopy (UPS) experiments have been carried out to investigate the interface properties at the C(60)∕p-sexiphenyl (6P) organic-organic heterojunction interface, including the interfacial energy level alignment and the supramolecular packing structures. As revealed by UPS measurements, the vacuum level is almost aligned at the C(60)∕6P interface, suggesting that the interface is dominated by weak intermolecular interactions, such as van der Waals and π-π interactions. In situ LT-STM experiments also indicate the formation of a molecularly sharp C(60)∕6P interface with hexagonally-close-packed C(60) layers nucleated atop 6P layer on graphite.