Synthesis of Cu-doped ZnO quantum dots and their applications in field emission

• Cu dopants modified the chemical environment and the optical properties of ZnO QDs.
• The Field Emission properties of ZnO nanorods modified with CZ QDs was enhanced.
• The enhancement is attributed to both the modification of ZnO QDs and the incorporation of Cu dopant.

Efficient field emitters of ZnO nanorods (NRs) after decorating of Cu-doped ZnO quantum dots (CZ QDs), by a facile hydrothermal method were reported. A layer with very tiny ZnO QDs was achieved along the axial direction throughout the whole ZnO nanorods. It's found that CZ QDs-modified ZnO NRs showed the best FE performance, comparing with eithor traditional ZnO NR emitters or the sample modified by pure ZnO QDs. By combining ZnO QDs and NRs utilizing surface modification engineering, a rough surface and a relatively sharp top of ZnO NR can be achieved, resulting in a significant improvement of FE characteristics. The enhancement may also be attributed to Cu-doping in ZnO QDs, which introduced more defects and free electrons in the conduction band of ZnO and also reduced the band gap. To shed light on the effects of Cu dopant, the morphology, microstructure and optical properties of ZnO QDs were further investigated in detail. The application of CZ QDs in FE materials may be expected to fabricate various FE devices by appropriate doping.