Multistep synthesis, growth mechanism, optical, and microwave absorption properties of ZnO dendritic nanostructures

Intriguing ZnO dendritic nanostructures have been synthesized by a two-step chemical vapor deposition process. Regular nanorods grow uniformly to the presynthesized ZnO nanowires on silicon substrate, the secondary nanorods are single-crystal hexagonal ZnO, and each nanorod grows along the [0001] direction. The relationship between the secondary-grown nanorods and the primary ZnO nanowire is not epitaxial due to the high temperature-increasing rate during the rapid grown process. The size and morphology of branches can be controlled by adjusting the temperature and duration of growth. Room temperature photoluminescence (PL) and mircrowave absorption properties of the ZnO dendritic nanostructures have been investigated in detail. The value of minimum reflection loss for the composite with 50 vol % ZnO dendritic nanostructures is -42 dB at 3.6 GHz with a thickness of 5.0 mm. Hierarchical nanostructures of this type are ideal objects for the fabrication of nanoscale functional devices.