Engineering sub-micron axial heterostructures in ZnO-C nanowires by low energy electron irradiation

Carbon-incorporated zinc oxide (ZnO-C) nanowires (NWs) demonstrate an enhanced variety of post-fabrication modification pathways such as electron beam treatment. Using localized low energy electron irradiation in a scanning electron microscope, axial heterostructures with varying defect fluorescence properties were engineered with sub-micron precision in ZnO-C nanowires. The electron-induced modification of the defect fluorescence of four types of nanowires, differentiated by their carbon content and defect fluorescence polarization, were characterized. Spatially extensive fluorescence quenching was observed in nanowires with lower carbon content. In higher carbon content nanowires, localized fluorescence intensity enhancement and color conversion from red to green were observed. In nanowires with an additional polarized emission component, the polarized component exhibited localized quenching independent of the unpolarized component. Additionally, electron beam induced deposition of amorphous carbon was achieved on ZnO-C NWs and found to be controllable by electron irradiation parameters. X-ray photoelectron spectroscopy measurements conducted on nanowire array samples implied that electron irradiation caused the replacement of zinc with carbon atoms. Finally, a method of visualizing electron trajectories through the nanowire by imaging the electron-enhanced fluorescence of surface contamination on the substrate was demonstrated and used to validate trajectories simulated by Monte Carlo simulations.