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3.75×10 11 cm -2 , the value from the TEM planview
images.
images can be also observed that the PF
shape is in better agreement.
Figure 2. Experimental and simulated 2D MEIS
spectra.
To investigate the geometrical shape of
the NPs, the system was modelled in two different
ways: i) as a hemisphere in the SiO 2
side on a pyramidal frustum in the Si matrix
side (further referred as PF) and ii) as a
sphere, half in the SiO 2 and half in the Si matrix.
The parameters of the PF shape are described
in Fig. 3 and the variable parameter
of the spherical shape is the radius.
To determinate the size and number
density of NPs, it were performed simulations
with several number densities for booth
geometrical models, and their the radius was
adjusted in order to keep the same Pb per
area, namely (Nt) Pb,MEIS = 2.26×10 15 atoms∙cm
-2 , value obtained by the MEIS measurement,
which is close to the one obtained
by auxiliary RBS measurements. The number
density obtained for the PF shape is
(4.2±1.6)×10 11 cm -2 , and, (5.3±1.7)×10 11 cm -2
considering the spherical shape. These values
of densities correspond to the values of radii
of (3.7±0.5)nm for PF shape and (3.2±0.4)nm
for spherical shape. The result for PF shape
agrees better to the value obtained by TEM,
namely radius of (4±1) nm and number density
of 3.7×10 11 cm -2 . Through the HRTEM
Figure 2. The PF geometrical shape model is described
by three parameters: the radius, the angle θ
and the depth h. The NPs anisotropy observed in the
TEM micrographs was taken into account, and is
related to (110) and (010) Si plane direction. Above,
(a) a lateral perspective at (110) and (c) (010) direction
of Si substrate, (b) seen from above and (d) from
below.
Here we have shown the capability of
MEIS analysis to characterize buried NPs,
which opens new perspectives for nanostructure
analysis in situ that can be of great interest.
References
[1] M. A. Sortica, P. L. Grande, G. Machado, L.
Miotti, Journal of Applied Physics 106, 114320
(2009).
[2] F. Kremer, J. M. J. Lopes, F. C. Zawislak,
and P. F. P. Fichtner, Appl. Phys. Lett. 91,
083102 (2007).
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