Alignment Growth Mechanisms of Rod-like ZnO on Zinc Substrates

Discontinuous films of ZnO particles were prepared on zinc substrates by air pre-oxidation process.The arrays of rod-like ZnO nano-/micro-crystals on zinc substrates were synthesized through hydrothermal processing with N2H4.H2O solution.It is found that the rod-like ZnO nano-/micro-crystals align well on the substrate surface with a unique crystallographic orientation.The experimental results suggest a free alignment growth mechanism for rod-like ZnO nano-/micro-crystals on zinc substrates.The crystallization habit of ZnO nano-/micro-crystals is to grow along with the c axis fast under hydrothermal conditions,thus the well alignment of rod-like ZnO nano-/micro-crystals only depends on the state of ZnO nuclei on the substrate surface.The states of ZnO nuclei on the substrate surface with a unique crystallographic orientation well agree with others,which regulates the alignment of rod-like ZnO nano-/micro-crystals.In temperature-dependent photoluminescence spectra,the thermal phenomenon of near band-gap edge excitons is observed in the temperature ranging from 30 K to 60 K,which identify two non-radiative processes and one negative thermal quenching process.