Photoluminescence and lasing properties of catalyst-free ZnO nanorod arrays fabricated by pulsed laser deposition

Nearly oriented ZnO nanorods with a mean diameter of ∼200 nm and length of 0.8 to 1.7 μm were prepared directly on lattice-mismatched Si (100) substrate by pulsed laser deposition without catalysts. In correlation with the detailed characterization of the morphology, crystalline structure, and oxide phases of the prepared ZnO nanorod arrays, the photoluminescence and lasing properties were studied. At room temperature, the ZnO nanorods emit strong near band edge emission resulting from radiative recombination of free excitons generated by ultraviolet light excitation. The random-lasing-like stimulated emission is observed at high optical pumping at room temperature, which centers around 382.8 nm and results from the superposition of guided lasing modes in different nanorods. The individual peaks as well as the stimulated emission as a whole show red shifts as the pumping intensity increases.