Fabrication and Growth Mechanism of Zn1-xCdxO Nanotubes by Thermal Evaporation Method

The Cd-doped ZnO nanotubes with Cd content of about 3.3at% were synthesized via a process of evaporating mixture of pure Zn and Cd powders and then oxidating in a wet condition. Field-emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM) analysis indicate that most of the nanotubes are of about 80-150nni in outer diameter, several micrometers in length, and about 20nm in wall thickness. Compared with photoluminescence (PL) spectra of the pure ZnO nanostructures prepared in the same condition, the room-temperature ultra-violet (UV) near-band-edge (NBE) emission of the Zn1-xCdxO nanotubes exhibite a slight red shift from 3.26e-V to 3.20eV, which is attributed to Cd substitution. It is suggested that the growth of the Zn1-xCdxO nanotubes follow vapor-liquid-solid (VLS) mechanism, and a possible growth process of the Zn1-xCdxO nanotubes is put forward. The Kirken-dall effect is considered to play an important role in the formation of the Zn1-xCdxO nanotubes.