CELERINET AÑO 7 VOL 2

CELERINET JULY - DECEMBER 2019
Fig. 1 SEM image of deposited gold particles at 575.15K
Fig. 2 SEM Image of different morphologies of the deposited
gold particles at 600.15K
Fig. 3 SEM Image in Dark Field mode showing closed
figure patterns of the deposited Au nanoparticles at
623.15K
From the SEM images, we can observe how
deposited gold particles make line and square
patterns over the NaCl substrates, this being
more evident for the deposited Au nanoparticles
at 575.15K (Fig. 1) and 623.15K (Fig. 3). This
behavior occurs because the gold particles
follow the most energetic favorable geometries
where it can be deposited with the least possible
energy and also to have the greatest adherence
with the NaCl surface, so as the temperature
is increased, the potential energy difference
between the NaCl substrate surface and the Au
nanoparticles rises. However, at 600.15K (Fig.
2), the square or closed like patterns of the
gold nanoparticles on the NaCl substrate seem
to diminish and the line like patterns are the
dominant ones, the reason for this phenomena
is because of the amount of potential energy
between the Au nanoparticles, and the NaCl
substrate reaches a saturation level for that of the
square or closed shape patterns, then when the
temperature is raised again reaching 623.15K
(Fig. 3) the closed shapes or squarelike patterns
become the most abundant ones again and are
even larger than the ones observed at 575.15K.
On Fig. 3, the darkfield mode was used
to observe the contrast between the Au
nanoparticles and the NaCl substrate. In
this figure, we are also able to appreciate
the abundance of Au nanoparticles and the
smoothness or defect-free NaCl substrate. Due
to the fact that Au and NaCl have a different
electronic density of states (DOS) TEM
analysis gives a great contrast between the NaCl
substrates and the gold nanoparticles. As can
be seen on Figures 3 and 4, the deposited Au
nanoparticles can be easily distinguished due to
the high contrast between the gold nanoparticles
and the NaCl substrate. Short deposition times
(1min) for the gold nanostructures may favor a
mono phase formation on the NaCl substrate.
By these series of experiments we can conclude
that a NaCl substrate makes a very suitable
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