Catalyst-Free, High-Speed Synthesis of ZnO Nanostructures
J. Pedersen, K.S. Teh
San Francisco State University, US
Keywords: Zinc oxide, nanowires, induction heating, vapor-solid mechanism
Abstract:We demonstrate a rapid and catalyst-free method of synthesizing ZnO nanostructures on Si(100) using a low-power (65W) induction heating process. Our preliminary results show that we could grow ZnO nanostructures of specific geometries ranging from ZnO nanocrystals, tetrapods, to nanowires, within several minutes. The growth is achieved purely via a vapor-solid (VS) mechanism, instead of the more commonly employed vapor-liquid-solid (VLS) mechanism that necessitates the use of catalyst such as Au. During the heating process, Zn powder was vaporized on inductively heated Ni in a controlled Ar/O2 environment. Zn vapor combined with oxygen to form ZnO, which precipitated on Si (100) surface, forming nucleation sites for further ZnO growth. We have successfully grown c axis-oriented ZnO nanowires of up to 3um long within 5 minutes in 0% and 1% O2 environment. Lower O2 content and post-annealing at 850C both favored the formation of ZnO nanowires over other types of nanostructures.