[Todos] LUNES 5 de diciembre - 13hs. - Seminarios DQIAQF - INQUIMAE

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Seminarios DQIAQF - INQUIMAE,  lunes 5 de diciembre - 13 hs.

Aula de Seminarios INQUIMAE - DQIAQF
Facultad de Ciencias Exactas y Naturales
Ciudad Universitaria - Pab. 2  -  Piso 3


INFLUENCE OF TITANIUM NITRIDE SUBSTRATE PROPERTIES ONTHE CARBON NANOTUBES
MORPHOLOGY OBTAINED BY CVD
F. Alvarez
UNICAMP, Inst. de Fisica "Gleb Wataghin"13081-970 Campinas, SP, CP 6165,
Brazil

Recent reports have shown that the growing of carbon nanotubes (CNTs) by
chemical vapour deposition (CVD) is influenced by the substrate
composition and not only by the catalyst material used in the procedure.
These investigations have shown that the substrates (buffer layer) affect
the kinetics of the CNTs growth, altering their diameter and length [1].
These reports also indicated that the stoichiometries as well as the
substrate´s nanostructure intervene in the process by different mechanism
not yet well understood. For instance, the presence of oxygen was invoked
as controlling ripening phenomena by reducing the difusión mobility of
precursor’s atoms on the substrate surface during deposition and thus
affecting the CNTs morphology [2].
In this seminar we shall present a comprehensive study of the effect of
the composition and nano structure of TiN buffer layers on the morphology
of CNTs growth by CVD. The studied samples were in situ obtained by
sequentially depositing TiN films on crystalline silicon and nickel
catalyst nanoparticles by Ion Beam Deposition (IBD) in a hydrogen
atmosphere at 500°C followed by growing CNTs from acetylene gas by CVD at
700°C. An auxiliary electrode near to the substrate polarized the
substrate to obtain well aligned nano tubes. The IBD technique allows a
fine control of the growing parameters as well as the material structure
and composition of the buffer layer. The presence of hydrogen is used to
control oxygen composition in the buffer layer. The buffer layer
composition and chemical Bonds were studied in situ by x-ray photoelectron
spectroscopy (XPS) in a UHV system attached to the preparation chamber. Ex
situ AFM, TEM, and SEM electron microscopy techniques were performer in
order to study the morphology induced by the different properties of the
buffer layers used in the carbon nanotubes growth. The correlation between
composition, nano struture and buffer layer morphology and its relation
with the CNTs characteristics are presented and discussed.

References:
[1] B. Bouchet-Fabre, A. Fadjie Djomkam, M. Delmas, C. Jin b, O. Antonin,
M.C. Hugon,M.F. Mayne-
L’Hermite a, F. Alvarez , T. Minea. Carbon 47 (2009) 3424.
[2] Amana PB, Pint CL, McJilton L, Kim SM, Stach EA, Murray PT, et al.,
Nano Lett 2009;9(1):44–53.