The evolution of catalyst layer morphology and sub-surface growth of CNTs over the hot filament grown Fe-Cr thin films |
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Authors: | M Akbarzadeh Pasha M Ranjbar A Shafiekhani |
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Institution: | a Physics Department, Sharif University of Technology, P.O.Box: 11365-9161, Tehran, Iran b Physics Department, Isfahan University of Technology, Isfahan 84156-83111, Iran c Physics Department, Alzahra University, Tehran 19938, Iran |
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Abstract: | 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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Keywords: | Carbon nanotubes HFCVD TCVD Growth process Catalytic layer Morphology evolution |
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