Fabrication and Energy Band Alignment of n-ZnO/p-CuI Heterojunction

N-ZnO/P-CuI heterojunctions are fabricated by growing undoped n-type ZnO thin films on p-type $\gamma$ -CuI (111) single-crystal substrates using radio-frequency magnetron sputtering. The ZnO films are identified to be columnar structured with $c$ -axis-preferred orientation by using X-ray diffraction and scanning electron microscope. Measurements of the energy band alignment of ZnO/CuI interface by using X-ray photoelectron spectroscopy result in a valence band offset of 1.74 eV and a conduction band offset of $-$ 1.37 eV, meaning a type-II band alignment at the interface. A typical diodelike behavior of the current–voltage curve indicates its possible applications in optoelectronics with further development.