Band alignment of ultra-thin hetero-structure ZnO/TiO2 junction

• Band alignment at the ZnO/TiO2 hetero-structural interface with different ZnO coating thickness was studied.
• The valence band offset was decreased with increased ZnO coating layer thickness.
• The interface dipole was responsible for the decreased band offset.

The band alignment at the ZnO/TiO2 hetero-structure interface was measured by high resolution X-ray photoelectron spectroscopy. The valence band offset (EZnO−ETiO2)Valence(EZnO−ETiO2)Valence was linearly changed from 0.27 to 0.01 eV at the interface with increased ZnO coating thickness from 0.7 to 7 nm. The interface dipole presented at the ZnO/TiO2 interface was responsible for the decreased band offset. The band alignment of the ZnO/TiO2 heterojunction is a type II alignment.

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