book of abstracts - IM2NP

A B S T R A C T S FRIDAY, JULY 2 N A N O S E A 2 0 1 0
11H20-11H40
Ordered growth of multi-walled nanotubes on Ge nanocrystals.
A. Capasso1, E. Waclawik1, J. M. Bell1, S. Ruffell2, A. Sgarlata3, M. Scarselli3, M.
De Crescenzi3 and N. Motta1 (1Queensland University of Technology, Brisbane, Australia; 2Australian
National University, Canberra, Australia; 3 University of Rome “Tor Vergata”, Rome, Italy).
1 – Introduction
Role of catalyst in carbon nanotubes (CNTs) synthesis is still under debate. In the past, transition metals have
been regarded as essential for carbon diffusion and subsequent nucleation of a graphitic tube-like structure.
Recent studies however show that particles of many other materials (metallic and semiconducting) could
fulfill this task, provided their size falls in the nanometer range. Semiconductor nanoparticles can decompose
the carbon gas source and thus result very active as catalyst in the nanotube synthesis. Ge nanocrystals in
particular have a much lower melting point compared to bulk: carbon can then diffuse inside the crystal and
allow the nucleation of a nanotube once the super-saturation regime is reached.
2 – Experimental details
In the present paper, we report a synthesis of CNTs on Si surfaces by using Ge as catalyst. The Si substrates
have been pre-patterned by nanoindentation, creating a grid of micro indents. Ge evaporation in ultra-high
vacuum leads to the formation of small Ge nanoparticles, which result ordered on the patterns. CNTs are
then grown by low-pressure chemical vapor deposition of acetylene. Multi walled nanotubes arise from Ge
nanoparticles in small bundles all over the surface, whereas on patterned areas a more limited yet quite
ordered growth occurs nearby the indents. The samples are imaged by Field Emission-SEM and AFM. EDX
elemental analysis and Raman spectroscopy provide further evidence of the metal-free nature of this
synthesis.
3 – Conclusion
Our results confirm that it is possible to grow CNTs without the use of any metal catalyst. By means of
surface nanoindentation, Ge nanocrystals can be assembled in controlled position and then employed as
seeds for the tube nucleation. This approach could be viable for integrating pure CNTs in specific sites on a
semiconductor, opening a way for the conception of enhanced electronic devices.
11H40-12H00
Boron Nanotubes and its properties: semiempirical investigations.
Zaporotskova I.V., Perevalova E.V., Zaporotskova N.P (Volgograd State University,
Volgograd, 400062, Universitetskii prospect, 100, Russia).
The problem of formation possibility nanotubular structures is actively discussed now. We considered the
fragments of single-wall boron nanotubes (n,n) (n=4,5,6,9,11,12). Calculations were carried out by IB-CCC
method [1]. The analysis of band-gap showed that all of them are semiconductors. Energy of deformation
decreases with increase of the diameter of B-tubes (n, n). We considered the B-nanotubes (n,0)
(n=4,5,6,8,12). In this case deformation energy is increases with increase of the diameter of tubes (n,0).
Calculations of boron tube (6, 6) which contained various defects of structure were obtained by the
semiempirical MNDO scheme. We research substitution imperfection of B atom by atom C, ions С+ , С-.
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