Optimization of photosensitivity of ultraviolet sensors based on ZnO nanorods etched with ZnO nanopowders using Taguchi method

In the present work, ZnO nanorods were synthesized on ZnO seed layer by a hydrothermal method and then etched in zinc nitrate solution, including ZnO nanopowder. To optimize the effective factors of etching solution such as zinc nitrate concentration, ZnO nanopowder concentration, and solution temperature, Taguchi experimental design with orthogonal matrix, L 16 , was used. Morphological and structural features of etched ZnO nanorods were analyzed by means of FESEM, AFM, and XRD. The morphological results showed that the etching process was accompanied by a decrease of about 23 nm and 480 nm in length and diameter of ZnO nanorods, respectively. XRD patterns showed that the (002) peak intensity is significantly reduced by nanorod etching. The UV sensor devices were fabricated in metal–semiconductor–metal configuration based on etched ZnO nanorods and the effect of the etching factors on UV sensitivity was systematically studied. Etching in high solution concentration and high temperature led to an increase in the sensitivity in the range of 10 3 –10 5 . Under optimal conditions (zinc nitrate solution of 0.01 M, ZnO nanopowder concentration of 0.0225 g/L, and temperature of 70 °C), a very high sensitivity to UV illumination was obtained (~ 1.1 × 10 5 ). In addition, a direct relationship was observed between the decrease in diameter (resulting from the etching process) and the increase in sensitivity of the UV sensors.