ZnO nanorods with two spatially distinct light emissions

Single-crystalline ZnO nanorods emitting two characteristic optical emissions from opposite halves of the nanorods were synthesized by thermal chemical vapor deposition using Zn/Al mixed powders. Energy dispersive x-ray spectra with transmission electron microscopy show a gradually decreasing Zn:O atomic ratio from the root to the top of a nanorod, and the averaged ratios at the two ends are ≈57.2:42.8 and 49.5:50.5. Room-temperature cathodoluminescence measurements show that the nanorods exhibit a sharp ultraviolet emission at 377 nm from one segment and a broad green band at 500 nm from the other, which is attributed to different oxygen concentrations along the nanorods. The luminescence behavior suggests further applications for nano-pixel optoelectric devices.