Radial and axial nanowire heterostructures grown with ZnO nanowires as templates

The recent research activities on density-control of ZnO nanowire arrays and growth of nanowire heterostructures will be discussed in this contribution. After a brief discussion of the general growth methods of ZnO nanowires, the encountered difficulties that prevent ZnO nanowires from being used as light-emitters were pointed out. One of the difficulties is the growth of homogenous nanowire heterostructures that is usually influenced by the shadowing effect associated with nanowire growth density. Then different strategies that have been adopted to tune the nanowire growth density were summarized and compared. For ZnO nanowire grown with PLD, it was proved that by introducing a wetting layer and adjusting the substrate-target distances the density of nanowire array can be tuned from 10 to 10^-2/μm². Based on the growth density control of nanowire array, a new strategy to grow axial and radial nanowire heterostructures were proposed and demonstrated, which was totally realised with pulsed laser deposition.