Effect of the Seed Layer Type and Precursor Concentration on the Structural, Morphological, and Photoresponse Properties of Hydrothermally Grown ZnO Nanorods.

This study proposes a simple and low-cost method of improving the photoresponse properties of ZnO nanorods by selecting optimal seed layer type and precursor concentration, which are parameters significantly influencing growth rate and morphology.When 0.025 M aqueous precursor solution was used, the obtained ZnO nanorods exhibited an improved vertical orientation and growth rate, showing directional growth along the (002) plane, as confirmed by field emission scanning electron microscopy. Moreover, ZnO nanorods (NR1) obtained on the seed layer prepared by oxidation of Zn films exhibited the faster growth rate than those (NR2) synthesized on the seed layer prepared by spin-coating method due to having access to a sufficient amount of Zn ions. The ZnO nanorods obtained at a precursor concentration of 0.025 M exhibited the highest photocurrent, dark current, and photoresponsivity, with the photoresponsivity and photosensitivity of ZnO NR1 exceeding those of ZnO NR2, owing to the larger surface area.