Mr. Azman Awang Teh Profile

Azman Awang Teh

at Univ Teknologi MARA

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Publications (2)

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Proceedings Article | 27 September 2012 Paper

A novel multi-wall CNT synthesis technique using conventional CVD with controlled pressure

M. H. Kara, M. H. Amir, A. Teh, R. Ahmad, M. Mahmood, Z. Awang

Proceedings Volume 8462, 846204 (2012) https://doi.org/10.1117/12.929351

KEYWORDS: Scanning electron microscopy, Carbon, Nickel, Chemical vapor deposition, Methane, Raman spectroscopy, Carbon nanotubes, Silicon, Argon, Thin films

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In this paper we have demonstrated successfully for the first time, a simple but efficient and reliable approach for the growth of multi walled carbon nanotubes (MWCNTs) with high degree of crystallinity, purity and density under a wide range of growth parameters. Multi-walled carbon nanotubes (MWCNTs) were synthesized at 800 - 950°C by thermal chemical vapor deposition (TCVD) method using a thin nickel film as catalyst and methane gas as carbon source. In this process, two substrates were placed in a long alumina boat inside a double-heater TCVD. One of the substrates was covered with a short upside down alumina boat. The prepared nanotubes were characterized by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) and it was found that, CNT growth on the covered substrate was improved in terms of quality and density compared to the other uncovered substrate. In addition, the nanotube diameter is reduced more than half. Results also revealed that the temperature gradient played a key factor for growth efficiency and purity of nanotubes. In addition, the diameter of CNT can be influenced by growth temperature too. The catalyst thickness and gas flow rate were found to influence the diameter and density of tubes, whereas the effect of synthesis time was on the CNT length. This growth technique is unique because of its simplicity, high efficiency and its ability to yield CNTs of high purity and density. This finding is supported by Raman spectrometry analysis.

Proceedings Article | 27 September 2012 Paper

Modeling and experimental verification of graphene co-planar waveguide transmission lines

Z. Awang, M. Kara, M. Amir, A. Awang Teh, M. Mahmood

Proceedings Volume 8462, 84620A (2012) https://doi.org/10.1117/12.929503

KEYWORDS: Graphene, Etching, Gold, Polymethylmethacrylate, Raman spectroscopy, Silicon, Nickel, Waveguides, Microwave radiation, Carbon

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In this paper we report the use of graphene for microwave integrated circuit transmission lines. Multi-layered graphene films were grown on Si wafers coated with SiO₂ and Ni using chemical vapour deposition. A modified procedure to etch graphene used in our work involved the use of Au on top of graphene which formed defects by breaking bonds of the underlying graphene, but our modified procedure enabled the etching process to be performed with the presence of PMMA masking layer. The etchant was made of 3HCl:HNO₃:8H₂O. Co-planar transmission lines of various widths and lengths were constructed on graphene to ensure compatibility with microwave wafer probes used in the measurements. The lines and the underlying SiO₂ layer were modeled using CST Microwave Studio electromagnetic simulator. The centre conductor width was 30 μm, while the spacing varied from 30 to 100 μm. The graphene parameters were subsequently subtracted out from measurements by curve-fitting the experimental results with simulation. Low frequency I-V measurements revealed conductivity of the order of 2.89 × 10⁷ S/m, but scattering parameter measurements of the samples conducted over 1 to 20 GHz revealed much lower conductivity, an effect which we think was the result of poor quality thermally grown SiO₂ substrates used in this experiment.

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