SSL Seminar Series 2004 No.1
Combined talks (two speakers)
Date: April 2 (Friday), 2004
Time: 4:00-5:00pm
Venue: Physics Conference Room (Blk S13 #M01-15)
Speaker I: Mr. Pan Hui
Title: Highly ordered Carbon nanotubes based on Porous Aluminum
Oxide: Fabrication and mechanism
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.
Speaker II: Mr.Sunil Singh Kushvaha
Title: STM studies of self-assembled nanostructures on graphite
and Si(001)
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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