Controlled Growth of ZnO Nanopagoda Arrays with Varied Lamination and Apex Angles

Aligned ZnO nanopagoda arrays have been grown on the silicon substrate with ZnO nanorod arrays by a hydrothermal and downward growth process. The concentration of ascorbic acid was used to control the growth direction and the degree of lamination of the ZnO nanostructure with a vastly reduced reaction time (from 24 to 2 h). Low turn-on and threshold fields indicate that ZnO nanopagodas are promising for applications in field emission devices. The ZnO nanopagodas exhibit a very prominent blue shift (10 nm) of UV emission and almost no green emission attributed to singly ionized oxygen vacancies at room temperature. The enhancement in deep-UV optical properties shall be advantageous in applications for nanoscale light-emitting devices. The polar surface concept can be used to understand the ZnO growth mechanism of nanopagodas. The appropriate substrates and reaction conditions lead to the growth of ZnO nanopagoda arrays with wafer-scale production. The large-scale ZnO nanopagoda arrays shall be beneficial in fabricating the novel devices, such as field emitters, ultraviolet lasers, and dye-sensitized solar cells.