Synthesis and in situ nitrogen doping of ZnO nanomaterials using a microwave plasma system at atmospheric pressure

A microwave plasma system operated at atmospheric pressure was utilized to not only synthesize ZnO nanostructures from a micro-sized Zn powder, but also dope with nitrogen simultaneously by changing the ratio of O 2 and N 2 gas mixture. When pure N 2 gas was used, ZnO was not produced due to oxygen deficiency. When the ratio of O 2 to N 2 was 10:90, 20:80, and 50:50 (vol.%), tetrapod-shaped ZnO rods with a diameter of 29.8 and a length of 256.5 nm were synthesized. When only oxygen was used, ZnO nanorods with a diameter of 626.5 and a length of 852.6 nm were primarily synthesized. Furthermore, it was confirmed from Raman and X-ray photoelectron spectroscope (XPS) analyses that the doping concentration of nitrogen increased with the increase of N 2 gas proportion to 50, 80, and 90 vol.%. The increase of the absorbance and the luminescence in the visible light region were confirmed by the change of the energy level due to the N-doping on ZnO. The most effective gas mixture ratio of O 2 to N 2 for synthesis of ZnO nanomaterials and in situ N-doping was confirmed to be 20:80 (vol.%). This work demonstrates the effectiveness of a microwave plasma system at atmospheric pressure which is available for synthesis of ZnO nanomaterials and simultaneous functional doping on it.