Epitaxial growth of vertically aligned highly conducting ZnO nanowires by modified aqueous chemical growth process

We report the fabrication of one dimensional conducting Al doped ZnO nanowires by spray pyrolysis and subsequent aqueous chemical growth (ACG) process. Al doped ZnO (AZO) thin film seed layers have been prepared with the Al concentration varying from 1 to 5 at% by spray pyrolysis technique. The structural analysis shows that the as grown films have hexagonal wurtzite crystal structure with a preferential orientation of (002). The AZO seed layers have an average optical transmittance of 80%. It is observed that 3 at% is the optimum value of Al doping concentration in ZnO, showing lowest electrical resistivity of 3.51×10−2 Ω cm with a carrier concentration of 1.52×1019 cm−3 and exhibiting n-type behavior. This optimum AZO (3 at%) films are used as a seed layers for the growth of vertically aligned one dimensional highly conducting ZnO nanowires by a modified aqueous chemical growth (ACG) process. The optical transmittance is found to decrease to the order 50% after the AZO nanowires grown upon AZO (3 at%) films. As grown ZnO nanowires exhibit an increased carrier concentration of 2.87×1020 cm−3 and a lower resistivity of 3.00×10−2 Ω cm in comparison to AZO 3 at% seed layers. Photoluminescence studies reveal that AZO seed layers and nanowires exhibit strong UV emission at 378 nm. Moreover, AZO nanowires show enhanced luminescent properties in the visible region ranging from 400 to 700 nm.