Improved Crystalline Structure and Enhanced Photoluminescence of ZnO Nanolayers in BiSe/ZnO Heterostructures

The Bi₂Se₃/ZnO heterostructure is a new combination of high- and low-band-gap nanomaterials that can be implemented for optoelectronic devices. The influence of the Bi₂Se₃ substrate on crystallization of ZnO nanolayers and charge separation at the Bi₂Se₃/ZnO interface reflects these important parameters, which affect optical and electronic properties of the heterostructure. Despite a few studies on Bi₂Se₃/ZnO heterostructures, the mechanisms of enhanced optical properties and correlation between optical and structural properties in such heterostructures are not studied in detail. In the present paper, we report on structure and optical properties of ZnO nanolayers with different thicknesses (10–150 nm) deposited by atomic layer deposition on planar and nonplanar Bi₂Se₃ nanostructured coatings. Crystallization of ZnO nanolayers grown on Bi₂Se₃ and Si substrates was analyzed by X-ray diffraction and scanning and transmission electron microscopy methods. Enhancement of ZnO photoluminescence in Bi₂Se₃/ZnO heterostructures in comparison to the photoluminescence of ZnO nanolayers of the same thickness deposited on p-doped Si substrates was observed. Correlation between the structure and optical properties of ZnO nanolayers in Bi₂Se₃/ZnO heterostructures is analyzed. Three complementary mechanisms of enhancement of optical properties of ZnO in Bi₂Se₃/ZnO heterostructures, based on charge separation at the Bi₂Se₃/ZnO interface, improvement of ZnO crystalline structure, and surface-plasmon–photon coupling, are proposed.