The effects of coumarin additive on the properties of ZnO nanostructures Original Research Article

In this study, we investigated the effects of coumarin presence in the growth solution on the properties of ZnO. Significant changes/improvements were observed in morphology and crystal structure. From the morphological studies, it was seen that the substrates were uniformly covered with rod/rice-like nano-structures and average diameters of the structures decreased with increasing coumarin content in the growth solution. Also coumarin affected the surface morphology, coverage density and uniformity of the shape of the structures. The X-ray diffraction patterns indicated that all diffraction peaks were well indexed to hexagonal phase crystalline ZnO. The greater intensities of (0 0 2) peaks in the patterns revealed c-axis orientation normal to the substrate. The crystallization of the samples was gradually enhanced with increasing coumarin volume up to 5%. When the coumarin volume exceeded 5%, the crystallization was affected negatively. The electrical resistivity values increased with increasing coumarin content and it was attributed to the decrease in carrier concentration originated by carrier traps at the grain boundaries.