The effect of annealing time and temperature on morphology and optical properties of ZnO nanostructures grown by a self-assembly method

Synthesis of zno nanostructures was achieved on glass substrate by the resistive evaporation ofmetallic zinc granules followed by dry oxidation process at 350, 450 and 550 ,c. characterization of theproducts with fesem and tem revealed that the structures obtained at 450 ,c are mostly nanorods withdiameters between 40 and 105 nm and lengths from 1 to 5 mm. one dimensional zno nanostructuressuch as ultra thin nanobelts, nanowires and nanorods were successfully synthesized at 550 ,c, withlengths up to several micrometers. xrd patterns indicated that the structures are crystalline and that znonanostructures grown at 550 ,c are fully oxidized and are crystalline with wurtzite hexagonal structure.pl measurements were carried out at room temperature and they revealed that there are three bandemissions; one sharp strong peak in the uv region and twoweaker peaks in the visible region. a strong uvemission was observed in the spectra of the zno nanorods and nanowires which confirms the good opticalproperties of products. the pl spectra also exhibited a considerable shift toward the shorter wavelength inthe uv region. it is clear that after the second annealing step photoluminescence of the 1d nanostructures,fabricated at 550 ,c, have improved, especially in the uv region.