Fabrication and Growth Mechanism of Zn_(1-x)Cd_xO 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 80-150nm 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 3.26eV 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 Kirkendall effect is considered to play an important role in the formation of the Zn1-xCdxO nanotubes.