Low-Temperature Facile Synthesis of ZnO Rod Arrays and Their Device Applications

Different morphologies of ZnO rod arrays with tunable photoluminescence (PL) were synthesized by vapor-phase transport deposition. The morphology and luminescence properties of ZnO rod arrays were found to be dependent on the deposition temperature and can be further tuned by postgrowth annealing treatment. Crystalline ZnO rods with intense UV emission at room temperature (RT) can be synthesized under a relatively lower temperature of 500 °C in a conventional tube furnace. ZnO rods grown at higher or lower temperature regions, however, showed additional defect-related emissions. Besides the commonly observed green emission from vapor-deposited ZnO rods, our samples also showed broad orange-red emission centered at ca. 620 nm. The origin of the different emission bands from the ZnO rod arrays was analyzed based on the annealing treatment in conjunction with the PL characterizations. Furthermore, two prototypes of optoelectronic devices (i.e., LEDs and FETs) were fabricated based on the as-grown ZnO rods. UV electroluminescence was achieved from ZnO rod arrays/p⁺-Si heterojunctions at RT, and FET based a single ZnO rod showed comparable transistor properties with previous reports on the ZnO nanorods grown at higher temperatures.