Synthesis and cathodoluminescence characteristics of caltrop-like ZnO nanostructures

Novel caltrop-like ZnO nanostructures have been synthesized on Si (1 0 0) substrates using a simple carbon thermal method at 1050 °C. Structure characterizations indicate that the as-prepared nanostructures have a single crystalline wurtzite structure preferentially oriented in the [0 0 0 1] direction. Cathodoluminescence measurements of ZnO nanostructures exhibit an intensive ultraviolet peak at 384 nm and four broad green peaks (at 492, 504, 524 and 524 nm, respectively), which can be attributed to the free exciton emission and the deep level emission, respectively. The prominent optical properties of the caltrop-like ZnO nanostructures make them promising candidates for fabricating optoelectronic nanodevices. A possible growth mechanism is also discussed.