Controlling the Growth Mechanism of ZnO Nanowires by Selecting Catalysts

Abstract

The effect of catalysts on ZnO nanowire growth was investigated by comparing the performances of Au, Pt, and Ag nanoparticles. Additional control of growth was achieved by implementing a substrate temperature of either 800 °C with a ZnO/graphite powder source or 500 °C with a Zn powder source. At 800 °C, the vaporliquid-solid mechanism plays a very important role when the Au and Pt nanoparticles are in the liquid phase. On the other hand, nanowires can also be grown on solid nanoparticles, that is, oxidized Ag at 800 °C and nanoscale cracks, that is, Pt at 500 °C, where, the vapor-solid is the only possible mechanism. At 500 °C, the vapor-liquid mechanism still dominates even though Au and Ag appear to be liquid, which is a result of high Zn vapor pressure.

Well‐arrayed ZnO nanostructures formed by multi‐annealing processes at low temperature

“…Firstly, the (002) peak intensity of ZnO nanostructures is significantly increased after step I compared with asdeposited film, then substantially increases after step II and step III. The growing mechanisms of formed well-arrayed ZnO nanostructures might include vapor-solid mechanism (VS) [8] and vapor-liquid-solid (VLS) mechanism [9], as described in our previous publication [7]. When the temperature increases, nuclear islands are quickly formed by the un-reacted zinc atoms on the surface of as-deposited thin film.…”

Zinc Oxide Nanostructures: From Chestnut Husk-Like Structures to Hollow Nanocages, Synthesis and Structure

“…Further study is needed for the knowledge of the process that is occurring in the vapor-solid process and of the role of Au/Pt nanoparticles in affecting the shape and size of ZnO particles, as well as their effectiveness in increasing quantities and homogeneity of the samples. Concerning the Pt-catalyzed growth of ZnO nanostructures, to the best of our knowledge, no systematic studies are reported and only two papers are shown on this subject [43,44]. …”

Growth of ZnO Nanostructures by the Reaction of ZnO Powder with Carbon Monoxide

“…[6][7][8][9][10][11] The VPT process, in which Zn, 6,7 ZnO, 8 and a mixture of ZnO and carbon [9][10][11][12][13][14] are used as sources, has been the most frequently used for synthesizing a variety of ZnO nanostructures. For the carbothermal reduction using a mixture of ZnO and carbon powders, Zn vapors formed in the temperature range between 800 and 1200 o C are transported via a carrier gas onto a substrate and deposited as a thin film or nanostructures of ZnO on the substrate at lower temperatures.…”

“…The reaction temperature used in this study was lower than that [9][10][11][12][13][14] in the carbothermal reduction method. Zn vapor generated by the reduction of ZnO powder by CO at a hot zone is oxidized to ZnO vapor and then deposited on the substrate away from the crucible:…”