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Paper   IPM / P / 14143
School of Physics
  Title:   The evolution of catalyst layer morphology and sub-surface growth of CNTs over the hot filament grown Fe-Cr thin films
1.  M. Akbarzadeh Pasha
2.  M. Ranjbar
3.  M.A. Vesaghi
4.  A. Shafiekhani
  Status:   Published
  Journal: Appl. Surf. Sci.
  Vol.:  257
  Year:  2010
  Pages:   1511-1515
  Supported by:  IPM
In this study a hot filament chemical vapour deposition (HFCVD) technique was used to prepare Fe-Cr films on Si substrate as catalysts for thermal CVD (TCVD) growing of carbon nanotubes (CNTs) from liquid petroleum gas (LPG) at 800 °C. To characterize the catalysts or CNTs, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy were used. The XPS spectra obtained at different stages of Ar+ sputtering revealed that in the depth of catalyst layers, the relative Fe-Cr concentrations are higher than the top-surface. SEM images of samples after TCVD indicate a significant CNT growing at the backside of catalyst layer compared with its top which is accompanied with morphological changes on catalyst layer such as formation of cone-shape structures, rippling, cracking and rolling of the layer. These observations were attributed to the more catalytic activity of the sub-surface beside the poor activity of the top-surface as well as the presence of individual active islands over the surface of the catalyst thin film.

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