Study Of Growth Morphology Of ZnO

The morphology of nano-/micro-crystals plays an important role in their physical and chemical properties, such as optical, electrical, magnetic, mechanical properties and catalytic performance. It is crucial to explorate the morphology dependent properties and subsequent applications of nano-/micro-crystals. Chemical bond can reflect the interaction of atoms or ions of materials, and the physical and chemical properties of materials depend on the characteristics of chemical bond. A relation between micro-structures of crystals and their macro-morphologies can be established on the basis of chemical bond, which facilitates the further understanding of crystal growth and design optimal experiments to synthesize nano-/micro-crystals with desired morphology.In this thesis, the formation of various ZnO morphologies is investigated by chemical bond method. In crystal surface, crystal growth happened accompanied with solute-rich clusters bonding to the unsaturated atoms, and meanwhile surface bonding energy was released. In ideal conditions, the mass transfer process is so quick compared to the surface bonding process, therefore, the later is the rate-determining process for crystal growth. A crystal growth model based on the energy change of crystal growth process was proposed, the quantitative relation between the relative normal growth rate of crystal face and the surface bonding energy was derived.With ZnO as a model crystal, the dependences of surface bonding energy on surface structures were analyzed, and diversified morphologies of ZnO crystal were successfully simulated in our model. Many methods have been explored to alter the growth rates on some crystal surfaces in order to manipulate the morphology of nano-/micro-crystals, including the addition of auxiliary agents. We simulated the morphology evolution of ZnO nanocrystals with the variation of impurity coverage ratio in{100},{011},(001) and (001) surfaces, respectively, in order to discover the optimal methods to control and alter the morphology of ZnO nanocrystals.The crystal growth model can be applied to the theoretical studies about the morphologies of various inorganic nano-/micro-crystals, showing good universality. Our work focuses on the formation and transformation of various morphologies at the atomic level, which can not only improve understanding of crystal growth, but also provide the guidance to experimental work.