Facile synthesis and ultraviolet lasing properties of ZnO microtubes

Single-crystalline ZnO microtubes with a conical tip, microtube flowers, microtube arrays and diamond-like polyhedrons were synthesized by a simple oxidation-sublimation process. No catalysts, carrier gases, or templates were used in the experiment. The morphology, crystalline nature, and composition of the as-synthesized products were analyzed in detail. The growth mechanisms of ZnO microstructures with different shapes were also discussed on the basis of the kinetics of nucleation, oxidation, and sublimation. The excitation power and temperature dependence of photoluminescence (PL) properties of the ZnO microstructures were investigated by using a spatially resolved spectroscopic technique. The results reveal that the microtubes obtained on the silicon substrate can produce stable UV lasing under low excitation power. The observed laser modes can be well explained with a whispering gallery mode model. Applications of these novel microstructures will be in the area of UV microlasers.