A) HIGHLY ORDERED CARBON NANOTUBES ON POROUS ALUMINIUM OXIDE: FABRICATION AND MECHANISM

Speaker: Mr Pang Hui

Abstract
Highly ordered carbon nanotubes (CNTs) are wildly pursued due to their unique properties. Anodic aluminum oxide (AAO) exhibits great possibility for this purpose. Here, CNTs based on AAO template were produced using acetylene or ethylene as the hydrocarbon sources with or without the presence of Co catalysts. CNTs grown on the Co-embedded AAO samples were normally confined within the nanopores of the AAO template. It was found that C2H4 normally requires 100oC higher pyrolysis temperature than C2H2 under otherwise identical conditions. The pyrolysis temperature is greatly reduced with the presence of Co catalysts. CNTs can grow out of the nanopores, if Co particles are present at the bottom of the nanopores, and if the nanopores are short in length or large in diameter. The graphitization of AAO-template grown CNTs was studied by Raman spectroscopy. The CNTs produced from ethylene are generally better in graphitization than those from acetylene, and the CNTs grown with the presence of Co catalysts deposited at the bottom of nanopores are better than those without Co catalysts or with Co catalysts coated on the entire inner wall of nanopores. The growth temperature is found not to play a critical role in graphitization.

B) STM STUDIES OF SELF-ASSEMBLED NANOSTRUCTURES ON GRAPHITE AND Si (001)

Speaker: Mr Sunil Singh Kushvaha

Abstract
A scanning tunneling microscopy (STM) studies performed for Ge and Si grown on HOPG (highly oriented pyrolytic graphite) and Si(001) respectively. In the former case, film remains thoroughly in island growth mode and is affected significantly by substrate defect. In this growth process lateral growth is favorable rather than vertical growth. There is no wetting layer present during the growth process of Ge on HOPG. It is expected that the surface morphology will be better and surface coverage will be nearly 100% if we grow Ge on HOPG at a lower substrate temperature. Furthermore, the growth mechanisms of Ge and Sb on HOPG could be compared. In the latter case of Si/Si(001) homoepitaxy study, step flow growth at high temperature and the roughening growth at low temperature have been well analyzed, but the intermediate state between these two extremes is still largely unknown. For optimization of the growth parameters for steady state in Si(001) homoepitaxy, different substrate temperature, flux rate, and deposition time will be tested. During the steady-state Si homoepitaxy, some nanopatterns will appear and these nanopatterns will be used as templates for other nanostructures growth.
 

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