Role of hexamethylenetetramine concentration on structural, morphological, optical and electrical properties of hydrothermally grown zinc oxide nanorods

Zinc oxide (ZnO) nanorods were grown on the glass substrates using hydrothermal method. Influence of hexamethylenetetramine (HMTA) concentration on the morphological, structural, optical and electrical properties of ZnO was investigated. Increasing HMTA concentration produces dense growth of nanorods and decreases the diameter from ~450 to ~150 nm and also modified the hexagonal shape of ZnO nanorods to circular shape. X-ray diffraction spectra revealed that the synthesized ZnO nanorod exhibits wurtzite structure. Shifting of absorbance edge from 3.30 to 3.36 eV with increasing concentration of HMTA was observed in the UV–Vis spectra. Photoluminescence studies showed the presence of defect related peaks such as zinc interstitial and oxygen vacancies. The observed blue shift in UV emission peak from 387 to 361 nm in photoluminescence spectrum also confirmed the decrease in the size of nanorods. Electrical studies showed the increase in the resistance with the increase in the HMTA concentration from 1.17 to 16.9 kΩ due to dense and reduced size of nanorod networks.