Molecular alignment and energy-level diagram at heteromolecular interface of quaterrylene and terrylene-3,4,11,12-tetracarboximide

Heteromolecular layers consisting of quaterrylene (QT) and terrylene-3,4,11,12-tetracarboximide (TTCDI-C ₁₂) were prepared on SiO ₂ surfaces and the electronic energy level alignment at TTCDIC12/ QT interface was examined. TTCDI-C ₁₂ layers were grown in nearly perpendicular orientation on QT layers by an ultraslow deposition technique, thereby achieving formation of a well-defined TTCDI-C ₁₂/QT interface. Atomic force microscopy (AFM) measurements ensured excellent surface flatness of each layer, surface roughnesses of which were comparable to that of pristine SiO ₂. Energy level alignment at the heteromolecular interface was evaluated by using ultraviolet photoelectron spectroscopy (UPS) and optical absorption measurements. No shift in energy level was observed at the heteromolecular interface, indicating that charge transfer does not occur and a dipole moment is not formed at the well-defined TTCDI-C ₁₂/QT interface.