Papers by Author: Chacko Jacob

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Authors: Joydip Sengupta, Sovan Kumar Panda, Chacko Jacob
Abstract: The effect of Fe and Ni catalysts on the synthesis of carbon nanotubes (CNTs) using atmospheric pressure chemical vapor deposition (APCVD) was investigated. Distribution of the catalyst particles over the Si substrate was analyzed by atomic force microscopy (AFM). Characterization by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopic measurements over the grown species is reported. The study clearly shows that the catalyst strongly influences morphology and microstructure of the grown CNTs.
Authors: Aparna Gupta, Chacko Jacob
Abstract: In this paper, we report a novel route to synthesize nano-sized cubic silicon carbide (3CSiC) powder by a chemical vapor deposition (CVD) technique in a resistance-heated furnace. The nanoparticles were deposited on the relatively cold region of a hot-wall quartz reactor. Hexamethyldisilane (HMDS) was used as the source material for both silicon and carbon. The presence of crystalline 3C-SiC was identified using powder x-ray diffraction (XRD) technique. From the XRD data, the crystallite size was also estimated to be in the range of nanometers (nm). A clear evidence of the particle size (~ 10 - 30 nm) was obtained by transmission electron microscopy (TEM). Selected area electron diffraction (SAED) was carried out on the nanoparticle assembly. The ring shaped pattern is a clear indication of polycrystalline particle formation. High resolution TEM (HRTEM) of nanoparticles was performed to study the crystal structure in detail. The nanoparticles were also characterized by Raman spectroscopy at room temperature. Finally, the influence of the growth parameters is also reported in the present study.
Authors: Yoichi Okui, Chacko Jacob, Satoru Ohshima, Shigehiro Nishino
Authors: Sovan Kumar Panda, Chacko Jacob
Abstract: β-SiC nanowires have been synthesized on etch-patterned wafers in a chemical vapor deposition (CVD) system without using any metal catalyst. The nanowires were grown selectively inside the ‘V-groove’ of etch-patterned silicon (110) substrate which was used as a template for nanostructure growth. Nanowire growth was hardly found on the sample which was not previously etched. The nanowires have a core-sheath structure with the SiC core surrounded by an amorphous SiO2 sheath layer. The etching of the patterned Si (110) wafers was carried out by a 50 % aqueous KOH solution. The SiC growth was performed in a resistively heated atmospheric pressure chemical vapor deposition (APCVD) system by using hexamethyldisilane (HMDS) as the single source for Si and C at 1150oC. The as-grown samples and the patterned wafers were characterized by field emission electron microscopy, energy dispersive x-ray spectroscopy, X-ray diffraction, micro-Raman spectroscopy and Fourier transform infrared spectroscopy. Etching is one of the key factors for nanostructure growth and the patterning in the wafer provides selectivity. The growth process was governed by vapor-solid (VS) mechanism.
Authors: Aparna Gupta, Chacko Jacob
Abstract: Selective epitaxial growth (SEG) of cubic silicon carbide (3C-SiC) was carried out on patterned Si (100) substrates using SiO2 as a mask. The growth was performed by atmospheric pressure chemical vapour deposition in a resistance-heated furnace using hexamethyldisilane (HMDS) as the source. It was observed that voids are the major defect in the case of heteroepitaxial growth of 3C-SiC on Si. Using selective epitaxial growth, the density of voids was reduced. Lateral epitaxial overgrowth (LEO) was achieved at selected areas where windows are arrays of stripes. The effect of temperature, window shape and size, precursor concentration, etc. on the SEG of SiC has been studied. After growth, films have been characterized by Nomarski optical microscopy, SEM, Raman spectroscopy and AFM. Faceted growth was observed along (111) planes inside smaller windows. Raman spectroscopy was used to identify defects and the presence of other polytypes.
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