Elsevier

Chemical Physics Letters

Volume 400, Issues 1–3, 11 December 2004, Pages 175-178
Chemical Physics Letters

Influence of Au catalyst on the growth of ZnS nanowires

https://doi.org/10.1016/j.cplett.2004.10.115Get rights and content

Abstract

We have successfully prepared dense and uniform ZnS nanowires with hexagonal wurzite structure on Au-coated Si substrate. The growth of the single crystalline ZnS nanowire follows the well-known vapor liquid solid (VLS) mechanism. The initial stages of the nucleation and growth processes of ZnS nano-particles on gold particles have been studied by atomic force microscopy (AFM) to derive insights into the critical nuclei size that promoted the growth of the nanowire. AFM images clearly show the three stages of the VLS growth process. Micro-Raman scattering detects various peaks related to the nanosize effects of the ZnS nanowires.

Introduction

Nanomaterials provide good learning ground for studying the quantum confinement effects and thermodynamic properties specific to the dimensional structures of these materials, which are expected to be different compared to the bulk phase. In a nanotube or nanowire, the finite size effect gives rise to a shift of the zone boundary in the phonon dispersion. Therefore, zone boundary phonons and activated defects due to lattice disorder can manifest in nanoparticles. Micro-Raman technique is a powerful tool for the study of such nano-related effects in nanomaterials. In the case of nanomaterials, quantum size effects come into play besides the enhancement of the surface-to-volume ratio. In addition, resonant Raman effect could give rise to new features in the Raman spectrum of nanomaterials due to resonantly excited zone boundary and disorder-activated modes, which are forbidden in the bulk material [1], [2], [3].

ZnS nanowire, a direct bandgap (Eg  3.7 eV) inorganic material with wide-ranging technological applications, can be synthesized using Au as the catalysts by simple thermal evaporation of ZnS powder [4], [5]. The well-known vapor–liquid–solid (VLS) mechanism [6] can be invoked to explain the growth mechanism of ZnS nanowires. In the VLS process, the liquid metal particles act as catalytic sites for absorption of gas-phase reactants. One dimensional (1D) nanostructures ensue from the supersaturated metal catalyst by precipitation. The size of the growing structure is restricted naturally by the size of the catalyst where it recrystallizes from. However, there are few direct observations of nanowire growth by VLS process. Recently, Yang et al. [7], [8] reported direct observation of Ge nanowires and GaN nanowires growth by VLS process using in-situ TEM. Besides TEM, atomic force microscope (AFM) can also be employed to observe the growth of nanomaterials at the initial stages.

In this work, AFM was applied to investigate the initial stages of the nucleation and growth processes of ZnS nanoparticles on Au. Such measurements allow us to probe the critical nuclei size that promotes the growth ZnS nanowires. Micro-Raman technique was also employed to study these nanowires in order to see if nano-related features not observable in the bulk-phase can be detected.

Section snippets

Experimental

ZnS nanowires were grown by thermally evaporating commercial ZnS powder onto the gold-coated silicon substrate, with the substrate temperature maintained at 700 °C under a dynamic vacuum of 1 × 10−5 torr. The powder was evaporated using high temperature Knudsen cell operated at different temperatures, with the growth time limited to 1 min. Before the cell reached the required temperature, the shutter was closed and the substrate was kept remote from the ZnS source to prevent deposition.

Results and discussion

Fig. 1 shows the SEM micrograph of the ZnS film prepared on silicon. Bulk quantities of densely packed nanowires, with an average diameter of about 80–100 nm and length of 10 μm, can be grown. Energy dispersive X-ray spectroscopy (EDX) shows that these nanowires are composed mainly of Zn and S. Grazing angle X-ray diffraction (XRD) confirms that all the reflected peaks with preferred orientation (0 0 2) can be indexed to ZnS hexagonal wurtzite structure with lattice constants a = 3.80 and c = 6.23 Å.

Acknowledgements

Ming Lin thanks the National University of Singapore (NUS) and Institute of Materials Research and Engineering (IMRE) for the support of a research scholarship. Professor Kian Ping Loh is grateful to NUS (Grants R 143-000-221-112) for funding this project.

References (13)

  • F.J. Brieler et al.

    J. Am. Chem. Soc.

    (2004)
  • X.M. Meng et al.

    Chem. Phys. Lett.

    (2003)
  • Y.W. Wang et al.

    Chem. Phys. Lett.

    (2002)
  • M. Abdulkhadar et al.

    Nanostruc. Mater.

    (1995)
  • J.F. Scott et al.

    Opt. Commun.

    (1972)
  • A.V. Baranov et al.

    Phys. Rev. B

    (2003)
There are more references available in the full text version of this article.

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