Local structural properties and growth mechanism of ZnO nanostrcutures

We investigated the growth mechanism of ZnO nanorods using in-situ extended X-ray absorption fine structure (EXAFS). ZnO nanorods were synthesized with a solution method and the structural properties around zinc atoms were measured by the in-situ EXAFS at every process. The synthesis was started with the solution of ZnNO₃ powder and H₂O. The solution was added with an amino acid complex and then heated up to 80degC. The EXAFS revealed that the zinc atoms of the solution had only two oxygen atoms without any second neighboring atoms, implying that ZnNO₃ is amorphous. When the complex was applied to the solution, the second neighboring Zn atoms appeared, although there was a substantial amount of structural disorders existing in the Zn-Zn pairs. This result suggests that the nitrogen ions in the complex play a role in clustering ZnO. At 80degC, ZnO was rapidly crystallized and the structural disorders disappeared. The in-situ EXAFS measurements provided the critical information of ZnO crystallization in the solution.