Although of the advancement in the field, the application of ZnO quantum dots is still limited by their poor charge transport performance. With the rapid advancement in nanotechnology, one-dimensional oxide nanostructures such as nanowires have been widely used for field emission-related studies. These nanomaterials exhibit significant coupling effects with ZnO quantum dots due to the latter’s remarkably large surface-to-volume ratio property. As such, a composite of ZnO quantum dots and one-dimensional oxide nanostructures have been widely speculated to be a potential material for efficient field emission enhancement. However, no definitive studies have been conducted to prove these assertions.
Recent studies revealed that the field emission properties could be significantly increased by nanowires with core-shell heterostructures. Consequently, heterostructures formed from different functional components have been found to bring new interface effects that can further improve the properties and functions of these materials. Equipped with this knowledge, Dr. Lei Sun, Dr. Enguo Chen, and Mr. Tailiang Guo from Fuzhou University explored the field emission enhancement capability of the composite structure of ZnO quantum dots and CuO nanowires synthesized by a mild solution method. The main objective was to investigate the field emission properties of the synthesized heterojunction composite structures. Their research work is currently published in the journal, Ceramics International.
In their approach, the Al2O3 transition layer was adopted as a good nucleation interface for the growth of ZnO, and it was deposited on the CuO nanowires by surface modification engineering technique. The modification process was specifically based on atomic layer deposition to enhance the surface characteristics of the CuO nanowire substrate and microstructure of the ZnO quantum dots. The structural morphology and composition of the prepared conducts, as well as their field emission properties, were studied in detail using various techniques such as scanning electron microscopy (SEM) and transmission electron microscopy.
The authors reported a significant improvement in the field emission performance of the [email protected]2O3/ZnO ternary heterostructure compared to pure CuO nanowires and ZnO quantum dots-CuO nanowires. For instance, the synthesized ternary heterostructure reported a field enhancement factor of 5798 and a turn-on field of 2.82 V/µm. The remarkable improvement in the field emission site stability and the electron conductivity was attributed to the easy transportation of electrons to the ZnO quantum dots due to the increase of the oxygen vacancies and the decrease of the electron transport barrier at the interface. Moreover, the amorphous Al2O3 transition layer also helped minimize the lattice mismatch between the substrate and ZnO quantum dots.
In summary, the authors investigate the field emission performance of ZnO quantum dot-CuO heterostructure nanowires synthesized by the mild solution method. Results showed improvement in performance with enhanced electronic conductivity and field emission site stability. In a statement to Advances in Engineering, the authors said their study would pave the way for the use of core-shell heterostructure nanomaterials for improving field emission performance.
Sun, L., Chen, E., & Guo, T. (2020). Field emission enhancement of composite structure of ZnO quantum dots and CuO nanowires by Al2O3 transition layer optimization. Ceramics International, 46(10), 15565-15571.