Experimental determination of quantum dipoles at semiconductor heterojunctions prepared by van der Waals epitaxy: Linear correction term for the electron affinity rule

We determined the band offset of eight layered heterocontacts consisting of combinations between SnS2, SnSe2, WSe2, MoS2, MoTe2, InSe, and GaSe. The comparison of offsets predicted by the electron affinity rule (EAR) revealed a systematic deviation. Due to the absence of structural dipoles in layered materials, this deviation corresponds to the magnitude of the quantum dipoles at the interface which allows the development of a quantum dipole correction term for the EAR. The corrected EAR is still a linear rule. The error margin of the corrected EAR lies well within the experimental error of photoemission spectroscopy experiments, thus proving the general applicability of Linear rules for the determination of the band offset. (C) 1997 American Vacuum Society.