Universidad Nacional Autónoma de México - CNyN

1st International Symposium on Nanoscience and Nanomaterials
Keywords: Atomic layer deposition, automation, growth rate.
The ever increasing need to build nanoscale devices has led to the search of alternative techniques to
deposit thin films on complex shaped surfaces. The required characteristics of the deposited films include
good conformality, step coverage, excellent uniformity, and high repeatability with precise control at atomic
scale. The atomic layer deposition (ALD) technique fits those requirements; since the deposition is carried out
trough surface reactions that are both self-saturated and -limited. ALD is a very powerful technique for
applications like capacitors for integrated circuits, diffusion barriers in transistor and others. In this work we
present the development of a fully automated atomic layer deposition system built at the CNyN.
Improvements over other similar systems and automation details are discussed. For example the reactant
(H 2 O) was relocated out from the main manifold to prevent oxide deposits on the walls of the manifold. This
help to maintain a constant pressure for at least 2000+ ALD cycles; compared to 200 ALD cycles when the
water is dosed to the precursor’s manifold. To characterize the system, we prepared Al 2 O 3 and TiO 2 films
from trymethyl aluminum (TMA) and tetrakis (dimethylamino) titanium (TDMAT) chemical precursors,
respectively, on silica substrate. We present the influence of the precursor type on the saturation behavior,
which leads to different growing rates of 1.1 Ǻ /cycle for the Al 2 O 3 and 0.9 Ǻ /cycle for TiO 2 . This work was
financially supported by CONACyT grants #83275 and #82984, and DGAPA IN114209-3. We acknowledge
the technical assistance of A. Tiznado, E. Medina, J. Díaz and P. Pizá.
P-013
ABOUT CONGRUENT SPHERE PACKING IN THE NANOPOROUS STRUCTURES
Larysa Burtseva 1,a , Vitalii Petranovskii 2,b
1 Engineering Institute of the Autonomous University of Baja California, Calle de La Normal, S/N, Col.
Insurgentes Este, C.P. 21270, Mexicali, B.C., Mexico
2 Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Apdo. Postal 14,
C.P. 22800, Ensenada, B.C., México
a lpb@iing.mxl.uabc.mx, b vitalii@cnyn.unam.mx
Keywords: sphere packing, optimization, packing model, density function, nanopores,
nanochannel, nanocavity.
In many cases atoms in the structural models appears as a hard congruent spheres. Crystalline
structures of simple metals have so called “dense packed structures”. For example, gold have face centered
cubic structure and in bulk state (that is in infinite volume) has space group Fm3m. While passing from bulk
to nanoparticles, translational symmetry is lost, and new coordination states appears for clusters and
nanoparticles, especially for those supported in nanopores of different supports. In this work the problem of
packing of congruent spheres (atoms) in a cylindrical container (nanochannel) of minimal height is
considered. While diameter of a channel (D) is less than diameter of sphere (d), no filling happens. Starting
from D ≥ d, in the range of relatively low D/d ratios, the local arrangement of atoms in nanoparticles
stabilized inside of nanochannels start to be sensitive to this ratio, in such a way opening possibility for one
more method of tuning of nanoparticle properties. Zeolites can be not only the “molecular sieves” but clusters
sieves too. This problem belongs to the optimization problems of Computational Geometry and is known to
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