Growth of ZnO nanowires on retroreflector microspheres and the resulting light channeling and plasmonic properties

We have investigated the growth of ZnO nanowires on curved BaTi03 retroreflector beads, as well as grov.1h of ZnO nanowires on flat substrates. Results indicate that the growth of ZnO aligned nanowire arrays occurs farther away from the Zn source in the retroreflectors, while the results are opposite for the flat Si substrates. In the case of the ZnO nanowires on flat Si, the nanowires formed in nearly aligned arrays are short and significantly thicker, suggesting that the growth occurs both longitudinally and laterally in this process, which is not the case for the grov.1h on the retToreflector beads. The SERS response of the nanowire arrays on the retrorefleCtors has been compared to random nanowires on flat Si substrates, and results show that the signal strength is 29 times greater in the case ofthe wires grown on the retroreflectors. Since one would only expect a factor of 4 enhancement due to the light reflecting properties of the retroreflector, it is believed that the enhancement in the SERS signal is due to light channeling by the aligned nanowire arrays.