Co3O4 Nanostructures with Different Morphologies and their Field-Emission Properties

• Published in: Advanced functional materials Vol. 17; no. 12; pp. 1932 - 1939
• Main Authors: Varghese, B., Teo, C. H., Zhu, Y., Reddy, M. V., Chowdari, B. V. R., Wee, A. T. S., Tan, V. B. C., Lim, C. T., Sow, C.-H.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 13-08-2007; WILEY‐VCH Verlag
• Subjects: Cobalt oxides; Field emission; inorganic; Nanostructures; Nanostructures, inorganic; Nanowires; Nanowires, inorganic
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200700038

We report an efficient method to synthesize vertically aligned Co3O4 nanostructures on the surface of cobalt foils. This synthesis is accomplished by simply heating the cobalt foils in the presence of oxygen gas. The resultant morphologies of the nanostructures can be tailored to be either one‐dimensional nanowires or two‐dimensional nanowalls by controlling the reactivity and the diffusion rate of the oxygen species during the growth process. A possible growth mechanism governing the formation of such nanostructures is discussed. The field‐emission properties of the as‐synthesized nanostructures are investigated in detail. The turn‐on field was determined to be 6.4 and 7.7 V μm–1 for nanowires and nanowalls, respectively. The nanowire samples show superior field‐emission characteristics with a lower turn‐on field and higher current density because of their sharp tip geometry and high aspect ratio.
Vertically aligned nanostructures of Co3O4 with various morphologies (the figure shows nanowires; nanowalls were also obtained) are made on cobalt foil in a controlled manner using a facile method. The morphological variations are achieved by varying the reactivity and diffusivity of the oxidizing species by creating a plasma environment in the system. The field‐emission properties of the as‐synthesized nanostructures are investigated.