Band alignment of ZnO/multilayer MoS₂ interface determined by x-ray photoelectron spectroscopy

The energy band alignment between ZnO and multilayer (ML)-MoS₂ was characterized using high-resolution x-ray photoelectron spectroscopy. The ZnO film was deposited using an atomic layer deposition tool, and ML-MoS₂ was grown by chemical vapor deposition. A valence band offset (VBO) of 3.32 eV and a conduction band offset (CBO) of 1.12 eV were obtained for the ZnO/ML-MoS₂ interface without any treatment. With CHF₃ plasma treatment, a VBO and a CBO across the ZnO/ML-MoS₂ interface were found to be 3.54 eV and 1.34 eV, respectively. With the CHF₃ plasma treatment, the band alignment of the ZnO/ML-MoS₂ interface has been changed from type II or staggered band alignment to type III or misaligned one, which favors the electron-hole pair separation. The band alignment difference is believed to be dominated by the down-shift in the core level of Zn 2p or the interface dipoles, which is caused by the interfacial layer rich in F.