Synthesis of Unique ZnO Structures via Hydrothermal, Solution, and Chemical Vapor Deposition Methods (2009)

Undergraduate: Chuan Zhang

Faculty Advisor: John Papanikolas
Department: Chemistry

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Zinc oxide (ZnO) is a II-VI semiconductor with a wide bandgap (3.37 eV) and a large exciton binding energy (60 meV), that adopts a hexagonal wurtzite structure. These favorable properties have enabled ZnO to be used in many applications such as transparent electronics, UV light emitters, and even catalysts in steam reforming reactions. Recently, there has been much research in synthesizing unique morphological structures of ZnO to enhance its optical and catalytic properties. Researchers have synthesized ZnO using methods such as hydrothermal, chemical vapor deposition (CVD), sol-gel, solution phase methods, etc…. In this thesis, we have focused on synthesizing unique ZnO structures from hydrothermal, solution, and CVD methods. In hydrothermal synthesis, needle-like ZnO rods of up to 15 ?m in length, as well as flower-like structures, were synthesized. We found the addition of polyethyleneimine (PEI) to the hydrothermal method significantly reduced the amount of flower-like structures present. In solution synthesis, temperature dependence on the morphology of ZnO structures was examined. It was found that at low temperatures (60-70 °C), ZnO ribbons were synthesized, while at higher temperatures (90 °C), a morphology shift to dumbbell-like structures was noticed. Lastly, from vapor-solid (VS) CVD, ZnO rods and tetrapods were successfully synthesized from a non-steady-state condition, while ZnO rods, wires, ribbons, and combs were synthesized from a steady-state condition.