Study on grow process and optical properties of ZnO microrods synthesized by hydrothermal method

ZnO rods were synthesized by hydrothermal method. Physical dimensions of the ZnO rods were changed systematically as a function of: precursor salt, deposition time, molarity, and temperature parameters. Nano and Microrods were obtained by using nitrate and acetate, respectively. The morphology was obtained by Scanning Electron Microscope. Zinc acetate resulted as the optimum precursor salt to study the synthesis process of the rods. Diffuse reflectance, photo and cathode luminescence, and x-ray diffraction techniques were employed to characterize the rods as a function of hexamine molarity/zinc acetate molarity ratio (MHMT/MZn). Optical results made possible to propose an energy diagram that presents different optical radiative desexcitation mechanisms. All rods resulted with an average energy gap of 3.36 eV and several energy levels into it associated to structural defects. The increase of neutral interstitial zinc and/or neutral oxygen vacancy shallow donors with the incorporation of HMT into precursor solution contributed to have a red shift of the ultraviolet emission.